Tested: Do Short Cranks Work For Tall Riders?

Sep 6, 2023
by Seb Stott  
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A standard 170 mm crank (bottom) next to a 155 mm crank.

For most mountain bikers, there's a pretty strong case that the standard 165 mm to 175 mm cranks are longer than ideal. As we covered in a previous article, there have been seven scientific studies that compared cyclists' power output, pedalling efficiency and pedalling style between a wide range of crank lengths. Surprisingly, unless you go to ridiculous extremes (120 mm or 220 mm), crank length doesn't seem to affect power output or efficiency much, if at all, even across a range as wide as 145 mm to 190 mm.

Moreover, three of the seven studies suggested possible benefits to shorter crank lengths. One found that shorter cranks reduced the time taken to increase power output in a sprint; one concluded that shorter cranks reduce fatigue when pedalling out of the saddle; another suggested that longer cranks could put more strain on the hip and knee joints. Combining this with the fact that shorter cranks reduce the chance of clipping pedals on uneven ground (a common cause of crashes and stalls), the case for shorter cranks on mountain bikes becomes even stronger - at least for most riders.

At 199cm / 6'7", Pinkbike skills scientist Ben Cathro is running 165 mm cranks and says he'd run shorter if he could.

Surely tall riders need longer cranks?

While the studies we looked at earlier found no downside to shorter-than-usual cranks (at least down to 145 mm), they were looking at the average output of a range of cyclists of different heights. And as rockstar-statistician Hans Rosling often said, averages disguise a spread. It makes intuitive sense that taller riders would perform better with longer cranks, so should very tall riders avoid shorter cranks, or even be running longer-than-standard ones?

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This figure from Martin & Spirduso plots the maximum power achieved by sixteen cyclists using five different crank lengths as a function of crank length to leg length ratio. The results are plotted relative to the maximum power each participant achieved with any crank. The parabolic line of best fit suggests the optimum crank length for maximum power was somewhere around 20% of leg length, but the spread of data suggests the optimum could be anywhere between 15% to 25%.

The biggest study into crank length by J.C. Martin & W.W. Spirduso looked at how maximum power output was affected by the ratio between a rider's leg length and crank length. The data suggested that the best crank length for sprinting was about 20% of the rider's leg length. This has been (over)interpreted by some to say that everyone should ride a crank length that measures exactly 20% of their inseam.

That would suggest the "ideal" crank for someone of average height would be around 161 mm for males or 150 mm for females.

This already makes a case for shorter cranks being standard, at least on bikes aimed at average riders (sizes small to large). But what about for someone who rides an XL or XXL like me? I'm 191cm / 6'3" tall, with a leg length of 93cm / 37", so that "20% rule" would put my ideal crank length at 186 mm. So should I be sizing up? Not necessarily.

Firstly, the relationship between crank length to leg length ratio and power output in the study above is very weak. There are a lot of outliers, with some participants recording their highest power outputs with a crank less than 15% of their leg length or more than 25% of their leg length. In nerd speak, crank length to leg length ratio was not a strong predictor of max power.

Secondly, the effect size of leg length to crank length ratio on power output was small. Looking at the parabolic line of best fit for all 16 cyclists, the predicted power output only varies by around 2% over the (wide) range of crank lengths from 15% to 25% of leg length.

Unfortunately, this study only looked at peak power output (sprinting), but a later study measured aerobic efficiency with nine male cyclists using 145, 170 and 195 mm cranks and, once again, found no significant difference.

All this means that crank length is unlikely to affect your power output much, if at all, if it sits between 15% to 25% of your leg length. For me, that would create a window from 140 mm to 230 mm. For someone properly tall like Ben Cathro, that window would be about 145 mm to 240 mm. Given the obvious benefits of better ground clearance, plus the other benefits discussed in the second paragraph of this article, it makes sense to aim for the lower end of that range. Based on this, crank lengths of 150-160 mm should still be appropriate for riders pushing two meters.



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Putting theory to the test

Despite all this, I wondered if a tall rider like me would find some compromises with short cranks, or if I could derive any real benefit. So I asked Hope for a set of their 155 mm cranks to try out and compare to the 170 mm cranks already fitted to the Hope HB.916 I have on test.

To compensate for the reduced leverage and higher RPM with a shorter crank, you'll want to run about a two-tooth smaller chainring for every 10 mm reduction in crank length, in order to keep the overall leverage between the pedal and the ground the same. So, ideally, the 32-tooth ring on the 170 mm crank should be compared to a 29-tooth ring on the 155's. Since Hope doesn't make odd-number chainrings, I rounded up to a 30-tooth, but could have equally chosen 28. If anyone's interested, the shorter cranks with the smaller chainring saved 34 grams over the stock setup. Whoop!
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Seb Stott
Location: Tweed Valley, Scotland
Age: 31
Height: 6'3" / 191cm
Inseam: 37" / 93cm
Weight: 189 lbs / 86 kg, kitted

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Swapping from 170 mm to 155 mm cranks, the difference is immediately noticeable. This is hardly surprising, but you're straight away aware that the stance is narrower and the pedal circle is smaller. Once I started pedalling, I soon realised that I wanted my saddle a bit higher. This is to be expected as bike fitters usually recommend setting the saddle to the same distance from the bottom of the pedal circle, but it was interesting to experience how the saddle felt immediately too low even though the distance to the centre of the pedal circle was unchanged. Putting my saddle up by 15 mm felt much better as I was able to fully extend my legs.

I went out for a short ride on the 170 mm cranks that features several steep and technical climbs and enduro-style descents, then I swapped to the 155's and did it again. Although the 155's felt odd at first, the differences soon faded into the background. On the steep and punchy climbs that always tempt me to start pushing, I didn't notice it being any harder with the shorter cranks. I also tried the 155's on a Canyon Strive for some longer rides and once again couldn't feel any downside. I had a go at a brutally steep climb that I've only attempted a couple of times before on a non-electric bike and failed both on both occasions, but this time I (just) made it. I'm not saying this proves shorter cranks are better, but it certainly boosted my confidence that they weren't holding me back. Elsewhere, there were a couple of sections where I usually clip a pedal or have to consciously time my pedal strokes to avoid hitting the ground, whereas, on the shorter cranks, I could spin freely.

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Accounting for suspension sag, the pedal is typically only around 100 mm from the ground at the bottom of the stroke, so it doesn't take much of an undulation or bump in the trail for the pedal to hit the deck.

When practising turns on the tarmac, I noticed that when I dropped my outside foot in a flat corner, my weight wasn't dropping quite as low as before. But when riding trails, I didn't notice a downside in the corners. One downside I did notice on the Hope bike was that the saddle was 15 mm higher than I was used to - as if the dropper post had 15 mm less travel. This meant the saddle was a little keener to make friends with my nether regions than I had gotten used to with the 210 mm dropper posts fitted to the bike. This is something that you can adapt to but isn't ideal now that I've got used to very long dropper posts. I also tried the shorter cranks on a Canyon Strive fitted with a 240 mm dropper and here there was no such issue with the shorter crank. I don't think this is a dealbreaker, but it's worth noting that a shorter crank effectively reduces the travel of the dropper post.

I can't say that I felt able to move around the bike any more than usual or ride with a flatter back, as Hope claim in their marketing material, but this may be more noticeable for less flexible or shorter riders. I've also seen it said many times that shorter cranks reduce fore-aft stability because there's a smaller platform between your feet, making it harder to avoid being pushed towards the bars when the front wheel hits a bump. I think this is nonsense because the cranks can spin freely on the bottom bracket anyway, so you can't resist your weight being pushed forward with your feet, no matter the crank length.

One thing I did feel was a reduction in thigh burn on long descents, especially in my front foot. On very long descents I occasionally ride with my weak foot forward for a few seconds to relieve muscle ache, but this seems less necessary with shorter cranks. The main benefit for me is that it's easier to grab quick pedal strokes to regain momentum on awkward terrain, especially when ground clearance is an issue.



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What's the bottom line?

If you're shorter than average height, or even not especially tall, I think it's worth considering shorter cranks for your mountain bike. Or if you are tall, it may still be worth downsizing if pedal strikes are an issue for you, or if you have tight hips or knees that cause issues with pedalling for long periods of time. The key word there is "or". You don't have to be short to benefit.

Both from my own tests and from the published science, I can see no downside even for tall riders, and the extra ground clearance is welcome on technical climbs and descents. In my view, cranks longer than 170 mm don't make much sense on a mountain bike that's designed to be pedalled over rough terrain while prioritising stability (i.e. keeping the bottom bracket low).

There are a couple of caveats. In order to keep your effective gearing the same, you'll need a smaller chainring (2 teeth per 10 mm reduction in crank length), and this may not be possible or desirable with certain frame designs, especially if you're already running a small chainring - some suspension systems aren't designed to run a 28-tooth chainring or smaller. If you always have a lower gear in reserve, this shouldn't concern you, but if you're regularly running out of gears on steep climbs and can't make your gearing easier, shorter cranks will effectively make your gearing harder, and that's likely to create more problems than it solves. Also, if you shorten the crank, you'll need to raise your saddle by the same amount. This could be an issue if you're already near the extension limit of your seatpost, or if you have a less-than-ideal amount of dropper post travel.

To be clear, for someone who is above average height, is reasonably flexible, and doesn't experience knee or hip pain with standard cranks, the only real benefit to shorter cranks that I can see is improved ground clearance. Depending on how and where you ride, that may not be a big deal so I'm not saying everyone should rush out to buy short cranks. But I can see no good reason why most bikes still come with 170-175 mm cranks even in the smaller sizes.

Short crank Pros

+ No perceptible loss of power, in real life or scientific tests, even for tall riders
+ Noticeably improved ground clearance when pedalling over bumpy terrain
+ Easier to grab quick pedal strokes between features
+ Slight reduction in leg muscle ache on long descents
+ Studies suggest possible advantages in the time to "spin-up" to peak power, standing pedalling efficiency and reduced joint stress.
Short crank Cons

- Reduced leverage should be compensated with a smaller chainring (and higher cadence) but this may be tricky with some frame designs
- A 10 mm shorter crank requires a 10 mm higher saddle, effectively making a given dropper post have less travel




Author Info:
seb-stott avatar

Member since Dec 29, 2014
306 articles

420 Comments
  • 225 6
 First off, this is a great article. I love that you cite a source and actually never thought about the seat height issue. We all know that more lever arm = more torque, so long crank arms are a knee-jerk choice for anyone with a basic physics education. However, it turns out that human legs can only spin so fast and they make peak power at some specific cadence. The longer the crank, the faster your foot has to spin at a given rotational speed, so it makes some kind of sense that bio-mechanics takes over and your leg's natural power output is the determining factor. Put another way, imagine using a ratchet wrench that's 2 feet long. Great for applying break-away torque, but quit terrible to use once the bolt is free. You can't spin the bolt as fast as with a shorter handle wrench. Surprisingly interesting for a topic which on the face of it is just a single measurement.
  • 20 6
 I'm interested in whether the shorter crank is a downside in those situations where you can only just grab one pedal stroke, for example on a techy climb, or just to grab a little speed before a drop or jump - if the gearing has been dropped, each pedal stroke delivers less energy
  • 16 10
 @mountainsofsussex: hence why you pair shorter cranks with smaller from chain rings.
  • 11 1
 @TheRamma: Though you get more torque, but with less forward motion, right?
  • 10 0
 @mountainsofsussex:
Going from 175s to 165s is roughly 2T of front chainring. That's not enough to make or break a single power move on tech climb. Being in the wrong gear or clipping a pedal/arm would likely have a larger impact.

On the hard-won tech climbs where every clean attempt is a victory, I'm taking that critical pedal stroke regardless of crank length. For me as a taller rider 165s did reduce the overall number of strikes in those scenarios, without impacting my bike fit in a meaningful way.
  • 19 0
 @mountainsofsussex: I have 175mm cranks on my road bike and 170mm on my mountain bike, and I feel like I'd prefer to have that swapped. I remember one of the articles often cited in favor of shorter cranks stated that longer arms were better for track sprinters who have to jump up to speed quickly from a standing start or low cadence, which in my head seems to be similar to the type of punching you do to make your way up ledges on a tech/steep climb, accelerate out of a track stand, or accelerate back up to speed out of a corner. On the road it's easy to sit and accelerate from 90rpm and you often need to hit peak power just to follow attacks and finish with the lead group, but on the mountain bike you're accellerating from a low cadence hundreds of times per ride/race and almost never have to produce peak power. I'd be interested in seeing a study that studies crank arm length and fatigue after producing an hour of low-high cadence microbursts instead of a steady state effort or maximal sprint.
  • 15 0
 I'm hanging this here in case anyone is intrested in preserving their lower limb joints, reducing rock strikes, and postural fatigue on the downhills
canfieldbikes.com/collections/cranks-chainrings
Canfield has cranks for trail and downhill that go down to 150mm in 5mm decrements. They are a good choice because there is good stock (hopes are harder to find) and are USD 200-300 than the boutique options. GXP spindle, but for 35 bucks they include a BB. Bombproof. Garbaruk has chainrings down to 26t.
  • 5 0
 @beeeefkirky: I was under the impression that track cranks were short to reduce the risk of pedal strike. When they’re going fast it’s not an issue but moving slower on a banked track brings your outside pedal perilously close to the boards.
  • 4 0
 @mountainsofsussex: if you're curious I left a bunch of comments talking about exactly this in the North Shore Billet Talon article on pinkbike. I go into a lot of detail.

In short, I prefer the short cranks overall for tech climbs, but from time to time there are spots where it's a bit harder because I can't quite squeeze in two strokes, and one stroke gives less power. Of course there's also the flip side - spots where I can now squeeze in two strokes but struggled before. And obviously now there are spots where I can just keep pedaling all the way through thanks to ground clearance. Lots more details in the NSB thread!
  • 2 0
 @mountainsofsussex: I think this would only be true if you dropped your chainring size. If you stay with the same chainring size, the energy would be the same with 1 stroke before a drop/jump/techy climb, and with the shorter length requiring a slightly shorter path of movement for your legs/feet, you might be able to achieve that same speed boost in a faster time. The only impact would be a slightly higher torque ask on the shorter cranks. I downsized from 170 to 155 cranks this season, but I stuck with my 30t chainring, besides raising the seat and getting used to the change in stance initially, it feels very comfortable and I do feel like I can sneak in an extra pedal stroke here and there on techy descents or climbs where I may have gotten a pedal strike before. Also worth noting, while technically you can't drop the seat as far once you swap, it may also be possible to switch to a longer drop post depending on frame clearance, since now your post isn't sitting as deep as it was before. So you can likely move from 150 drop to 180, or from 180 to 200.
  • 2 0
 @nosmallplans: They are and the smaller cranks also help with spinning faster (important on a bike with no gears). I don't think the article was saying long cranks were best for track racing in general, rather that they were better than shorter cranks for accelerating from a standing start (like one would in a 1km TT on the track).
  • 5 0
 @beeeefkirky: I have quite opposite experience. Being a 180cm tall, on a 26" Rune with previously 32x11-36 gearing I moved from 175mm SLX to new 165mm SLX. As the 32t ring has been too small I got made custom 34t ring for new cranks.
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With shorter cranks I immediately could accelerate much faster even from track-standing, bunny hopping is quicker and I am always in one harder sprocket (smaller). Even in uphill on rougher trails I am able of gaining higher speeds and preserve it because my pedalling is very fluent. If obstacle surprises me in bad gear I just quickly stand and smash few pedal strokes. With shorter cranks like this the biomechanics is much better. If I realized that before I would got made 36t ring instead of 34t. Also the almost speedless overcoming of higher roots in steep climbs is easier.
  • 2 2
 So what is you're ideal crank arm length and what most people should use??
  • 6 4
 @mountainsofsussex: And then theres the Ebike equation to throw in for all the cheaters.
  • 5 0
 @mountainsofsussex: How often are you actually using MAXIMUM power for a single pedal stroke? Pretty rare, or you'd never get up anything bigger than the first techy climb you ever did.

Timing is _way_ more important than absolutely maximizing force. And you'll find that shorter cranks are easier/faster to bring around to get to that high force position at the right time. As well as very likely providing room for more than one single stroke, providing more power overall than a single stroke even with longer cranks.
  • 3 2
 @HappyBiker19: DING! That's why the chainring thing is dumb. Reducing the chainring by 2 teeth from 32t-30t takes almost 6 inches out of the roll-out against a 51t cog. So you might get marginally less power from the 20mm shorter lever arm, but you'll also be losing a large amount of forward motion from the smaller chainring. Lose-lose. Don't mess with the chainring, work on timing instead of max power.
  • 1 0
 @sdurant12: How many of those tight spots that only allow one stroke are you truly using _absolute maximum power_ provided by, say, 175mm cranks? Not many, so the trade-off gets leaned heavily towards the spots where short cranks let you get in extra strokes.
  • 1 1
 @mountainsofsussex: My son's bike has 165 mm cranks vs 170mm on my own bike. My experience is that the one pedal stroke on a techy climb requires less effort but you gain less distance because you go through your stroke quicker because of the smaller arch.
  • 5 0
 @HappyBiker19: I don't think so. 360 degrees is 360 degrees. The amount of force changes but the degrees of rotation, which are fixed to the chainring stay the same.
  • 2 0
 Agreed, great article! If we're getting nerdy, leg length being defined to the inseam is helpful but everyone's anatomical length of femur (upper leg) and tibia/fibula (lower leg) could vary greatly and cause our heads to explode as we go further down the rabbit hole of biomechanical efficiency and crank length. Seb's pros and cons are all we need. Shorter=better most of the time. Wait...but what about Q-factor!
  • 7 0
 @justinfoil: I dunno dude. I've done one of my favorite climbs with "standard" gearing (i.e. 30t w/ 11-48 ) w/ my 155 cranks, and it was terrible. I went to a 28t oval and then in the end a 26t and finally it felt roughly the same to climb with (and close to same climb time) as my other bike (my benchmark hardtail). The higher gearing blew my legs up halfway into the main climb (20min 13% grade). I did 3-4 rides with this bike that sucked until I reduced the gearing again. I figured out that my 29er now has the same gear ratio (including tire height) as my previous 27.5 bike had with a 30t and 175 cranks. And now I am happy. Cadence is still only 80avg, which is my natural cadence anyway on a trainer. I DGAF about 6" less of roll-out, my downhill times have substantially improved with the confidence of being able to rail anything without clipping pedals or the ability to get another pedal stroke in thru rough stuff. In tech climbing punchy stuff maybe I'm just up one gear than normal, to get the extra forward movement. But feels no different and the increased pedal clearance has been more beneficial for me. The ONLY con for me is reduced top end speed, which, honestly for a Downhill/Park Day I could go up 4teeth, but you again lose chainring clearance. So still not 100% a con.

NOT going back to 175s on this bike. Or even 165s.
  • 5 1
 @climbbaby: but 360 degrees of crank revolution now pushing a 28t cog (VS 32t cog with 175mm cranks) IS less chain distance covered. You'll complete a revolution quicker and cover less ground.
  • 4 0
 @justinfoil: Tend to agree here as well. Hate to repeat the 'BMX Background' trope, but in this case it's really valid. BMX starts and the sprint are maximum power down (Slalom/4X to a degree). I don't have much knowledge on Trials, but could see a few situations there. However, there isn't that much max power for most riders in daily MTB riding. Yes pro racers in MTB and maybe XC finish sprints. However, 'max power' on a climb is either a seriously steep climb -OR- someone is in the wrong gear.
  • 1 0
 @bman33: even for sprints and such, remember that power is force by distance over time. "max power" does not depend on force alone, such that a lower force can produce the same power if that force is produced for more time. Getting max force to the ground in a sprint is a combination of force from the crank length and time from the cadence. You might be able to make more force by standing on a long crank, but you won't be able to spin it around as in order to make that same force again. And since a sprint or even a gate start takes more than one pedal stroke, crank length is not the end all be all even for that situation.
  • 1 0
 @mountainsofsussex: I swapped from 175 to 165 a while back and it's true it's a down side. it's rare that it's an issue in the real world but I've had a moment here and there where the clocking of my cranks wasn't exactly right for the terrain and I was used to the 175 getting me over the rock. not a big deal but perhaps something to think about. personally I prefer the 165 anyway.
  • 5 2
 I question your "basic" physics education when you fail to acknowledge the lever arm is attached to a geared system. Let's see your study. The conclusions of this article have been proven over and over and over again, yet plenty of numnuts still object and wander off into their own pseudoscience. Don't look up!!
  • 3 0
 @justinfoil: it's rare. Basically only on climbs where I have to do an endo turn or some adjustment hops or something and I'm starting from a standstill and trying to get up a ledge.

But again, I'm someone who absolutely loves technical climbing, and overall, I much prefer the short cranks. Nicer for climbing and nicer for descending. 6'4 on 145s.
  • 1 0
 @beeeefkirky: John Cobb the tri saddle design guy, has done some research on shorter cranks for road riding. I don't know if his studies are still about on the net.
  • 2 1
 @Moonie2123: it's funny you say this. the study is that: a study. they collect results and feedback from participants. it's different from calculating the theorical torque from a fixed force on the crank. the theorical torque says longer cranks is more leverage, that's.. actually science.

what the study says is "yes but in practice it's not enough for people to feel a big difference and you get used to it". but you _still_ do have more leverage. in other words it's saying most people probably will prefer the trade offs of shorter cranks (I know I do!)

trusting a paper or site without understanding it is just as bad, if not worse, as "don't look up". it's in fact what causes people to no longer trust anything they're told. trust is very hard to re-establish once lost.
  • 3 0
 @justinfoil: Exactly. And let's not forget that input force being put at pedals is result dependant on work of your legs and ANGLE at which you push your feet. The farer you are pushing your feet the less force you put in pedals.
Then there's biomechanics, too.
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Simply, for someone can be more beneficial to perform higher RPM on shorter cranks to gain fluent level of even lower power to the ground. Someone else will prefer burst of low RPM power and then just cruise before another burst.
  • 1 0
 @mountainsofsussex: As someone that went from 170s to 160s i can say they are a huge improvement especially on techy climbs. I did not go down two teeth though, I stayed at 32t. I noticed i was into the granny gear a little more often at first but after a couple rides it was back to normal and after 8 months on the 160s i use the granny gear way less than i used to. I am climbing techy stuff i could never climb before.
  • 2 1
 @beeeefkirky: we’ll said, MTB is constant accelerations, unless you are on a smooth gravel climb where you can spin or a long downhill. Therefore we shouldn’t be talking about power, instead we should be talking about torque when discussing crank arm lengths for MTB.
  • 4 0
 @fluider: Exactly, talking about people mostly consider the bikes side and forget the bio-mechanical side. Yes you will have to put more force through your feet to create the same torque at a shorter crank length, but as you say, since the pedal is closer to your bio-mechanical rotationpoint (your hip) the same force from your muscle will create a high force on the pedal. So basically it probably will even out a lot and is probably the reason why the is so little influence from crank length on power output except for the extreme ends.
  • 1 0
 @mrkkbb: Power is torque over time. And since torque alone won't power you out of a corner because it takes more than one single pedal stroke to go anywhere useful, we definitely need to talk about power.
  • 1 0
 @justinfoil: I think the point is that there are far more low-rpm accelerations out of corners or short single-pedal stroke "punches" to get over a root/ledge occuring during a mtb ride than a road ride (at least in my experiences). Power may be equivalent in those instances, but torque would be higher, requiring more strength, which would place different stress/demands on the body which might not be meaningful in the short term, but could add up over the course of 2 hours.

TLDR: The studies of efficiency and power align well with road demands but we don't have the data to make that claim about how power is delivered on a mountain bike in the real world. They may translate well to mountain biking, but they also may not.
  • 1 0
 @iduckett: "Cadence is still only 80avg"

Cadence comparison being between 30t and 26t? That means you're going slower, of course it's going to be easier.
  • 1 0
 @beeeefkirky: Low-rpm accelerations aren't hurt by short cranks. Data shows that they help acceleration, probably due to reduced foot/pedal speed and reduced leg flex.

When you need to accelerate from standing to running, do you take the biggest steps you can (long crank)? Or somewhat small to medium steps (shorter crank) to get up to speed?

You're not using MAX POWER for getting over ledges. The timing is way more important. If you needed every single inch-ounce of torque from a 175 crank to get over something, you'd fail with just a misplaced foot on the pedal, or a half-second mistiming.
  • 1 0
 @p1nkbike: okay. With the same gear you have more torque. Agreed. But what if, bear with me here, we could somehow adjust the gearing of the bicycle. Could be cool. You could, for example, use a smaller cog on the crank. We could call it a "chainring" and sell different sizes. And then if you switch to cranks that are 10% shorter you could buy a chainring that's 10% smaller to have the same amount of leverage
  • 2 0
 @justinfoil: Comparing 175mm cranks to taking the longest strides possible seems like a false comparison.We're not running the longest cranks possible (e.g., the 220mm cranks tested in the studies - shown to be worse) but something pretty normal/in the middle.

I'm not saying timing isn't important or that short cranks don't offer that advantage in situations where clearance matters. But for the trails I ride, I'm not likely to clip a pedal, and the few situations where I ned to worry about it (e.g., going up ledges) it's all about timing - I'm just as likely to clip a 175mm crank as a 165mm crank because of suspension movement. The very concrete advantages of shorter cranks aren't universally relevant.

But I'm also not talking about advantages/disadvantages like clipping a pedal. I'm curious about power and fatigue. While you're right someone may not need every last bit of torque, it is reasonable to think that reducing the amount of torque needed in high-torque situations by a little bit would add up over the course of a ride or event. It would be a marginal gain perhaps, but cyclists love those.

My main point is - I'm skeptical of making generalizations about efficiency etc. when the sports have such different power-delivery demands. The tests that suggest short cranks are not a disadvantage all most closely replicate the demands of road riding. The little bit of research that has looked at low-rpm accelerations DOES seem to be in favor of longercrank arms in those contexts, but even then I'm not sure that translates because it is looking at maximal efforts (which, as you have noted are pretty uncommon). So we're left with conflicting information all of it lacking ecological validity for mountain biking. I'm not saying you're wrong nor am I saying I'm right, but I'm saying the studies we draw from leave out an important aspect of mountain biking which may (or may not) meaningfully change the results.
  • 4 0
 @beeeefkirky: "I'm just as likely to clip a 175mm crank as a 165mm crank because of suspension movement."

No, not unless you limit the suspension to 10mm shorter when using the 175 cranks. Shorter cranks, just like a taller static BB height, given the same suspension settings, WILL reduce pedal strikes. That's a fact.

As you've said, the science shows different things for different situations, and not all of those situations apply to pedaling bikes on trails. However, what they do show is that the overall concern of "loss of power" from short cranks is pretty much nil. Even the low-rpm accel data is countered by the data that shows short cranks help you get out of that low-rpm area faster. Plus gears. We have gears, we're constantly changing the relationship between pedal movement and wheel movement, and we deal and it's good!

I'm just trying to say that the benefits (clearance, leg flex, pedal speed, "easy-over-the-top" feel, timing) greatly outweigh even the perceived deficits (overall power in all situations? seat height?), let alone the actual deficits (max power in a small sample of situations, a tiny bit of seat height), and both the data and many many experiences support this.
  • 1 1
 @justinfoil: Yes - just pointing out that some people love to think smaller cranks "make you spin faster" or "you'll spin faster", when in fact, you don't. You just spin the same and go slower (as you mentioned). I do think the smaller circle makes for smoother pedaling though.
  • 82 0
 My little daughter is now crying because i stole her cranks
  • 2 0
 Well, jokes aside... My gf is short and looking for short cranks. NX was supposed to exist in 155... Nowhere to be found. Other options are 300€.
So... Looking at kid cranks, and even there, found nothing
  • 3 0
 @R-M-R: bought these Canfields for my girlfriend in 155. They are fantastic.
  • 5 0
 @Uuno: Trailcraft sells a 152mm crank (for children's bikes).
  • 6 0
 I'm going to steal my daughter's balance bike = maximum ground clearance!
  • 1 0
 m.pinkbike.com/news/ask-pinkbike-short-cranks-for-emtbs-axle-to-crown-heights-and-how-to-avoid-going-over-the-bars.html
This article reminded me of this.

No, SX cranks cannot be bought at least in France/Europe, believe me I've tried.
Other options are expensive, like the Canfield at 200€+ and having a less common chainline limiting chainring choices. Thanks for the suggestions but I already researched all those.

Finally found Chinese cheap Goldix children cranks, ultra cheap, bad quality, but perfect to try out something else than 170. My gf got the 155 and that's a perfect starting point to maybe get something high quality for the long term, in 150-160
  • 1 0
 @Uuno: Canfields are not cheap but the chainline is not a big deal, with GXP chainrings you can get just about any offset you need.

Another option that is cheap is the Suntour cranks, I think they go down to 152. But they do have a weird chainring...

I have some Chinese cranks too (can't remember the name) - yet to really test them though
  • 24 1
 In the interests of proper English: the effective drop does not change, a 210 mm dropper still drops 210 mm at full drop. However the effective saddle height at full drop is increased, by whatever saddle height increase one chooses to accommodate the shorter crank arms, so the effective, lowered saddle height is increased (or higher - if that's the way your brain thinks of it) which may or may not mess with one's descending mojo.
  • 5 4
 Exactly. Who needs there seat that low anyway? DH bikes don't run the seat that low.
  • 2 2
 @stubs179: This exactly. Huge droppers are the new 820mm bars. Even with only a 180mm dropper I hit my tire way before I get anywhere near my saddle.
  • 44 23
 The real opportunity here is to build bikes with lower bottom brackets to lower your COG, IMO. I've spent the last decade beating the shorter cranks drum but it's a hard sell. Kudos to PB for following up on this.
  • 76 2
 Man bb's are already pretty low idk about this one
  • 47 0
 I've been on short cranks (165mm 34"inseam) BEACUSE of low BB

Please don't go lower!
  • 5 5
 Agreed! I bought a 29er and put 27.5 wheels on it and 145 cranks and it's pretty sweet with the low BB. Wish I could get a full 29er with a similarly low BB, or at least a mullet set up (with a still reasonable seat angle). Having sized down the frame as well it makes for a very very fun combination.
  • 3 0
 Agreed - I built my last hardtail with 75mm BB drop (unsagged) to take advantage of 165mm cranks. It rides so well I have no doubt this will eventually be a geometry change we'll see throughout the industry.

I'm 6' with long legs, and was riding 180mm cranks before. I very much prefer the 165s.
  • 11 0
 The new trendy bikes are getting so low that soon enough you won't even be able to pedal. When will modern mountain bikers just accept they want strider bikes.
  • 9 1
 I currently ride with 175mm cranks, and a BB of 347mm. Occasionally, this causes a pedal strike while pedaling - but not so often as to be a major deterrent. Does this mean that I could ride a 165 or 160mm crank and expect similar performance from a BB of 337mm? Likely - but with a huge consideration...

BB height is also a determinant in much higher-consequence situations when descending. Assuming I am generally descending with my cranks parallel-ish to the ground, lowering the BB an additional 10-15mm would introduce more chance for toe-smashing/pedal catching incidents and crashes. Unfortunately, these hang ups at speed can often result in foot/ankle injuries and abrupt over-the-bar type crashes. No bueno.
  • 4 2
 This is exactly the wrong answer… Pedal strikes are happening because they’re lowering the bottom brackets. If they lower them anymore they will be bouncing off of the rocks and you won’t have to worry about pedal strikes.

Everytime I ride with shorter cranks I always feel tippy and off balance from the shorter stance.

Pedal strikes were never a thing until they started with the whole
Long low slack movement.
  • 6 1
 @Saidrick: Trials riders use short cranks and don't seem to have tippy nor off balance issues....honestly, I think it's just a matter of getting used to it.
  • 5 0
 Lower em until we’re making sparks at bottom out
  • 10 0
 Yes to shorter cranks. No to further lowering BB heights. They are plenty low enough as it is these days. I've been running 160mm cranks for a couple years on one bike, still have 170mm on another. Swapping between the two is like going between 27.5 and 29 wheels. You notice it for about 30sec, then you're just riding your bike. What I do notice big time are fewer pedal strikes on the bike with shorter cranks.
  • 3 1
 I’ll take centralized center of gravity over low center of gravity.

Change my mind.
  • 2 0
 Its called your feet are flat when you descend so regardless of how short or long your cranks are your going to start bumping your bottom bracket on things if it gets lowered
  • 2 1
 @nickfranko: Nah, you're free to be wrong and stubborn. Im not gonna stop you.
  • 1 0
 I switched from air to coil shock and needed 165s immediately. No lower BBs ,please.
  • 4 1
 @Bro-LanDog, @markb2392, @Saidrick;

It's true, pedal strikes are more common now than twenty years ago when BBs were high, and it's true we're pretty close to the limit for most people on most terrain to keep their cranks off the trail.

Thankfully, lowering the BB in proportion to crank length reduction won't make things worse, assuming your strikes happen when the crank is at 6 o'clock. If a crank is shortened by 10 mm, a 10 mm lower BB won't change this scenario.

If you're striking the chainring, however, the lower BB will make things worse.

Ground strikes rarely happen at sag; they usually happen when the rear suspension compresses through a dip in the trail. Adding low-speed compression damping to the rear shock (ex. using a "trail" or "pedal" mode whenever practical) greatly reduces ground strikes.
  • 3 2
 @KJP1230: That's a legitimate concern. To be fair, though, in 30 years of riding I can only recall a couple of times I hit my foot/pedal on something hard enough to cause a problem when riding with cranks level. YMMV, of course, depending on your riding style/local terrain/luck.
  • 4 1
 @Saidrick: Better not try riding motos, then. Curious how those trials folks do all that stuff with their stance so narrow...

Seriously, if you put short cranks on and left them for a month you wouldn't notice anything.

That said, the good news here is you don't need to put on short cranks, because your power output is just fine regardless, so run whatever you like.
  • 2 1
 @mjlee2003: What we discovered back when we tried this (ie ~11" BB height with 150mm cranks) is that chainring clearance can become a problem in some places. To some extent this is compensated for by using a smaller ring to keep the gearing feeling normal, but not entirely.

You'll never hit the actual BB, of course. At least not in any scenario I can imagine.
  • 1 0
 @waltworks:

Trials riders are the best of the best at balance. Hans Rey can keep his balance without pedaling. The rest of us, good luck…

That’s like comparing the driving skills of F1 drivers to a daily commuter.

I have tried shorter cranks, extensively: my dh bike has 165mm’s , compared to my 175mm/172.5mm’s. I would put longer cranks on the dh bike, but it would have all kinds of pedal strikes from all the extra sag/ travel.
  • 5 1
 @Saidrick: I was referring to motorcycle trials, but bike trials, same story.

There are beginner trials riders in the world, not just professionals. There are even (ahem) folks who have dabbled in it for 20+ years and still suck...but I digress.

You can balance fine on moto foot pegs with a pretty darn narrow stance, or on 200mm cranks on your custom Zinn humongobike. You'll adjust just fine too any scenario.
  • 2 0
 @R-M-R: I'm not worried about pedal strikes, I'm worried about smashing chainrings
  • 1 1
 Counter intuitivly, lower bottom brackets decrease side to side stability, not increase it. They do however increase fore-aft stability and make the bike more manouverable. All of it is extremely marginal, to the point of being useless, as your cog is somewhere around 1000mm off the ground, moving it to 995mm off the ground by dropping your BB 5mm isn't likely detectable
  • 8 0
 @hughlunnon: "lower bottom brackets decrease side to side stability, not increase it."

It's complicated. And yes, a few millimeters isn't a big difference, so this can be more academic than practical, though there have been bikes with BB heights that differ by many centimeters.

A higher BB results in a slower rate of rotation when imbalanced - i.e. the rider does not tip over as quickly - so, in that sense, it increases stability. Unfortunately, it also means the displacement is greater for a given angle, so the corrections need to be larger - and, therefore, slower - which makes the more stable bike more difficult to navigate. Bit like how an enormous boat is more stable than a small one, yet the handling is slower, so it can be more difficult to keep the large boat traveling within a narrow band.

So, we can see the taller bike produces oscillations of longer wavelength and larger amplitude, and vice-versa for the lower bike. The lower bike may experience a greater number of oscillations, but it has narrower error bands on the intended path of travel and the lateral displacements between the centre of mass and the base of support are smaller.

Stability is often discussed as a proxy for safety. I feel the lower bike is more agile and less likely to result in a crash (excluding the possibility of a crank or chainring ground strike), which makes it the safer bike. As such, I feel the discussion of stability can be misleading.
  • 7 0
 @R-M-R: you are my favourite commenter on Pinkbike. You should have an article series, really. So much design knowledge. Paging @brianpark
  • 1 0
 @Saidrick: yeah they were.
  • 3 0
 @pbandjam: Yes please!
  • 1 0
 @Bro-LanDog: Yeah but we’re talking about reducing crank length by 15mm. Surely that means we can reduce BB height by like 5mm on bikes with already low BB, and around 10mm for bikes with higher BB.
  • 1 2
 @nickfranko: Crank length affects weight distribution but not center of gravity. Putting any crank length on and your center of gravity will still fall over the BB
  • 2 0
 @Tustinite: your center of gravity will be higher. Draw a triangle with 2 equal sides then change the length of the 3rd side.
  • 1 1
 @RonSauce: it's a very small difference though. With a relatively acute angle, changes in length of the third side don't raise the height of the triangle much. So if you shorten your cranks 5mm and drop your BB 5 mm you will end up lower overall! Only changing crank length, you will end up taller if you keep your legs equally straight with both setups
  • 1 1
 @sdurant12: a small difference is not zero difference. You're arguing that the fact isn't facting hard enough.
  • 1 1
 @RonSauce: I didn't argue that it wasn't a difference. I was just pointing out that it's a small difference.

With an inseam of 28 inches = 711 mm (which is apparently the average inseam height for an average height (5'Cool male, an isosceles triangle with a base of 330mm (165 crank length) has a height of 692 mm. If you shorten crank length to 155 (310mm base), then you get a height of 694mm.

Now before you reply saying "you're arguing that 692=694 lol but that's not how facts work", let me clarify. I'm not arguing that 694=692. I'm saying that for 1cm of extra ground clearance you merely raise your CoG 2mm when your pedals are level.
  • 1 1
 5 foot 8 inch male. Pinkbike decided to make an emoji out of the 8 )
  • 1 1
 @RonSauce: note that I'm not the guy you were originally responding to, I just decided to chime in.
  • 1 1
 @sdurant12: if you really want to be a pedant you would factor in hand placement.

If you personally don't feel 1-5mm differences thats fine, and probably good for you. Keep in mind there are people who CAN feel these differences though. I can tell the difference in pedal and shoe thickness, ill get used to it in about 45 seconds but I can tell. I can also tell if my saddle height is a few mm off, so all these inconsequential-to-some numbers are still factually different numbers.

Crank length effects saddle height and your center of gravity. It isnt going to effect reach, but it might make you want to adjust your stack height too.
  • 2 1
 @RonSauce: I never said it was "inconsequential" or that "I couldn't feel it" (although the latter is true in this case, as I simultaneously dropped my BB height, so overall ended up lowrer overall).

I just made the point that the difference in standing CoG is smaller than the difference in crank length.
  • 17 0
 Interesting the see how this develops on bikes over the next 5 years. Right now it seems that major OEM (sram, shimano, even raceface) suppliers don’t make cranks shorter than 165mm, which would have to change for mass adoption of this trend across the industry. Further, if short cranks gain mass appeal will see frame designers creating bikes with lower bottom brackets, or are there limitations with how far is too far on that front? It is an interesting thought that we could see a bigger spread of crank lengths across a size run of bikes (S-145, M-150, L-155, XL-160). This could be a rare case where no frame standards need to change in order for most riders to experience improved ride quality, and I’m all for that. Thanks Seb for this great content!
  • 16 2
 The problem with all the crank length messing about is that on most bikes altering your chainring size will have a significant effect on the suspension characteristics, so while a shorter person might want a smaller crank, you would give them more antisquat. This combines with their less than average bodyweight > damping and means an already firmer than average ride gets even firmer.

So basically if we were to move to a wide spread of crank lengths (and a correspondingly wide range of chainrings to match) then you also need to tune the shock and the frame kinematics to each size. Not just a small tweak but something quite significant.

Where this could be worked easier is to have smaller wheels/mullet chips (on smaller sizes) to eliminate the need for the chainring size reduction and kinematics changed - that would allow you a pretty good spread of cranks without changing the ring size, and hence keeping the bike riding as designed.
  • 14 0
 @benpinnick: My real world experince of dropping 10mm of crank length, i never noticed the "effective" 2 tooth change of the chainring, i've got 12 gears out back, with a huge spread, I just use the gear that works. I did however notice the improved ground clearance, mainly cos i've less snapped pins in my pedals.
  • 2 0
 @benpinnick: The antisquat value is also calculated based on a certain height of the center of gravity. I forgot the sign of that relation and will confess I am too lazy to look it up. But my vague recollection is that tall people get more AS from the same design. If that's correct, it would actually sort of work out well.
  • 3 0
 @ak-77: Yes and no, they get more AS from riding a large size (front contact patch is further away from the rear contact patch) but less AS from having a higher COG.
  • 3 0
 @benpinnick: Shouldn't bike companies already be doing this for riders of different weights/size?
  • 7 0
 @benpinnick: Correct me if I’m wrong, but don’t kinematics already need to be tweaked between sizes of a given bike to accommodate different measurements within the frame? Also, do you agree that having bike designers design those frames around a specific chainring/crank size window, even if they are different then current norms, would create better-riding bikes compared to what is currently starting to happen; riders putting short cranks/small rings on bikes that were designed around a 170/175 or 30/32?
  • 4 1
 @benpinnick: The antisquat difference isn't enough for most riders to detect unless you're changing by 4+ teeth, though. I could sneak in your garage and swap your 30t for a 28t and you wouldn't even know.
  • 3 0
 @benpinnick: True, though there's such a range of pedaling anti-squat values on the market that a change in chainring size barely adds to the noise. Even within your own designs, you've bounced between slightly over 100% to over 150% (modeled on size Medium, 30:42 for 29" and 32:42 for 27.5", using my own CoM location for size M). And I've enjoyed all of your bikes I've ridden, especially the AM9, which was at the high end of the range - which I ride with a 28T sprocket!

@HMBA106: THANK YOU. It's so nice to see people understanding this! I introduced size-specific kinematics (SSK) in 2017 for exactly that reason. As I said at its debut, the difference in kinematics across the size range of a given bike model without SSK is greater than the difference in kinematics between different bikes of a given size (±1σ from median).
  • 1 0
 @R-M-R: What bikes featured your SSK? Or was this more of a theoretical thing.
  • 2 0
 @plustiresaintdead: Stucture SCW 1 was the first, followed by those listed below. Not all of them featured it on all kinematic parameters, and some other companies may have copied without mentioning it in their marketing, in which case I may not be aware of it. Also, bikes using SSK don't necessarily feature kinematics designed by me, only the SSK concept.

Cannondale
Marin
Last
Merida
Prova
Rocky Mountain
Silverback
Yeti
  • 1 0
 @plustiresaintdead: Ah, then in this case my long legs and high COG might be compensated by a smaller chainring.
I ride a frame that was originally designed for a double crank and have a 32t oval mounted currently. I've ridden it with 26/36, 30 and 32 oval singles an I don't remember feeling any clear difference in suspension characteristics so I don't think I am very picky in this respect.
  • 1 0
 @R-M-R: Interesting! I personally believe, without much data to support besides my experience, that riders perceive antisquat angle (Force due to antisquat) more so than antisquat percentage. EG what percent of your pedaling power is transferred to upward motion, rather than the somewhat abstract idea of what percent of your weight shift is countered. Any thoughts on this?
  • 1 0
 @plustiresaintdead: My thoughts are it sounds like those are the same thing.

Also, let's put a question mark beside Prova as a user of SSK. I have it in my database that they're using it, but that didn't sound right and I can't find the source. I may have marked the wrong manufacturer; have to investigate this.
  • 1 0
 @R-M-R: I don't think they are. In this case we will look at a tall and short rider on the same bike. The suspension might be transferring say 40 newtons of force into extending the suspension to fight rearward weight transfer. This will provide say 80% antisquat to the tall rider and 100% antisquat to the short rider. In my experience, both riders will describe the suspension as having the same amount of "efficiency" and traction, or how much the platform stiffens under pedaling.
  • 2 0
 @plustiresaintdead: That's not how it works. The suspension does not transfer a fixed amount of force, it transfers a fixed portion (for a given rider, sprocket combination, and point in the travel) of the chain tension. This portion of the chain tension creates a ratio of the forward acceleration to anti-squat. That's the basis for how the anti-squat percentage is determined.
  • 1 0
 @R-M-R: What units would you use to describe the vertical component of the chain tension? I think this is what I'm getting at.
  • 2 0
 @plustiresaintdead: Either Newtons or Newton-meters (as a torque, about the instant centre). But keep in mind the vertical component comes from the chain tension; it does not exist in absence of chain tension.

For example, when coasting, the pedaling anti-squat force is zero. When pedaling very softly, the pedaling anti-squat force is very mild - but so is the squat force, since the squat force comes from acceleration, and acceleration is low when pedaling softly. That's why pedaling anti-squat is expressed as a ratio.

As you can see, this is why pedaling anti-squat is usually greater when using a higher drive ration (outermost sprockets). For a given chain tension, acceleration is lower, so the ratio of chain tension (and, therefore, anti-squat force) to acceleration is usually higher. The chain force vector acts on a different angle when using different cassette sprockets, so some bikes are exceptions to this trend, but it's rare.
  • 1 0
 Correction: "drive ratio", not ration. sigh ... but if you think my typing is poor, you should see my handwriting!
  • 1 0
 @R-M-R: thanks for all the info, I’ll have to read it a few more times to wrap my head around it!
  • 1 0
 @waltworks: I would, but I design bikes for a living and regularly swap rings in order to manipulate AS numbers, so I guess Im cheating. I also advise tons of customers after the purchase and one of the common threads is 'My suspension has started feeling harsher, is it warranty?' followed by 'Have you changed your chainring size recently?' to which the answer is often yes. Other people would seem to be sensitive to it too.

I do agree though 2T is probably not enough for most people, hence I only brought it up on the suggestion of a 15mm crank length spread, which would be at least 4, perhaps even 6T of chainring difference. At that point these things start to come into play. Especially when you consider that the smaller crank user probably wants less AS ideally anyway in order to offset the additional damping effects of the shock, to then ratchet up the AS correspondingly seems almost perverse.
  • 2 0
 @HMBA106: You're correct, and that of course happens, if you run out today and take a current frame and radically alter the crank length from whats probably a 170 (Does anyone actually supply bikes with 175s as standard any more?) you create unintended consequences which start to offset the upside of what you're doing. In order to fully realise the benefits you'd need to plan ahead of time to ensure those changes didn't create other negative effects. So yeah, you need to plan for it for sure.

Of course all these things are subjective, as more than one person suggests not everyone would notice the difference, not everyone likes the same AS level and the ring change might improve the ride for 50% of people who do it. But, as a bike designer you want to try to ensure that the ride is similar across your size range.

Don't get me started on gravel bike fork trail! I've been working on gravel bikes recently and you'd not believe the variations in trail that some brands have across their sizes. It's just nuts that you'd allow that to happen.
  • 2 1
 The idea that one needs to reduce the chain ring size is crazy. Keep the 32t and shorten the cranks. Problem solved.
  • 2 0
 @benpinnick: I design bikes for a living too! Very cool. Generally speaking I've found that customers can't detect even pretty large differences in chainring size/antisquat, but YMMV. I know I can't really tell - most of my perception of how the suspension is functioning happens when I'm not pedaling, after all. For folks swapping from 175s to 160s or something on their current bike, a couple of teeth won't be noticed.

But regardless, my interest is not really in swapping cranks on existing frames. It's building frames from the ground up for shorter cranks, where I'd just pick the chainring size/antisquat desired as part of the usual design process.
  • 2 0
 @benpinnick: "as a bike designer you want to try to ensure that the ride is similar across your size range."

Does that mean you're implementing size-specific kinematics? It would be an especially good time to do so, now that you're doing more carbon frames. I know you've always preferred to work solo in your design process, but I'm happy to collaborate!
  • 1 0
 @waltworks: This is absolutely false. I had a Revel Rascal that was two very different bikes when climbing loose terrain when switching between a 30 and 32 tooth ring. With the 30t it squatted and easily broke loose. I did multiple back to back tests on the same climb with both chainrings, it was noticeable.
  • 3 0
 @Henchman21: I'm not necessarily questioning what you felt, but the chassis would have greater anti-squat with the 30T, so that observation doesn't line up with expectations. Breaking loose, however, does line up, as greater anti-squat usually reduces climbing traction.
  • 2 0
 @Henchman21: That's the opposite of what the kinematics should do (the 30t should squat less), so maybe there was another variable you didn't control for.
  • 3 0
 @R-M-R: You're clearly forgetting about Pro-Flex "Dig-in Technology", where the marketing materials clearly explained how anti squat (although that term was not yet in common usage yet) actually pulls the tire down into the ground. ;-)

Just kidding, in case that wasn't clear, and actually I always really appreciate your insights!
  • 2 0
 @thekaiser: Forgetting it? Quite the opposite! I lusted after those things and - moreso - the Givin Vector linkage fork! I'm also grateful for the Vector being the first (slightly) mainstream mountain bike front linkage and the lessons it taught me for when it was my turn to design front linkage kinematics.

Both the "Dig-in" concept and the J-shaped front axle path sounded sensible, but turned out to be incorrect. That's how we learn, though, and Bob Girvin was a pioneer.
  • 2 0
 @R-M-R: Could this observation of @Henchman21 be a case where too much antisquat leads to the reverse effect and causes pedal bob that is 180 degrees out of phase with what you would get with zero AS?
  • 2 0
 @ak-77: Astute observation! Best I can say is ... maybe?

The Rascal has higher than average pedaling anti-squat, especially in higher drive ratios, which I forgot to check before responding to Henchman21.

Bike designers have finally been learning that 100% anti-squat at level-ground sag is not the ideal number for pedaling efficiency. (The reasons for this are complicated: our legs and torsos impart vertical forces, climbing usually occurs on steep inclines that produce greater sag, and the rider-chassis system has a resonant frequency.) There's no value that's perfect for all riders in all situations, but it's clearly over 100%. (Again, it's complicated: lower values result in better traction, which can improve efficiency in extreme situations; produce less chain tug on the drivetrain, which just feels nicer; and can produce a resonant frequency in the suspension that cancels out the vertical forces from the rider's biomechanics.)

As an experiment, I purchased a bike with nearly the highest pedaling anti-squat on the market and fitted it with a 28T chainring. My biomechanics are particularly smooth. This should be an ideal combination to produce pedaling jack (negative squat), yet I still observe a small amount of squat on steep climbs. That's only one data point for a complex system, but it suggests a bike's pedaling anti-squat value may have to be a real outlier on the high end to produce pedaling jack, such that a larger chainring would improve efficiency by reducing this effect. Alternatively, there could be resonance or something else reducing his efficiency.

My guess is that he correctly noted reduced traction from the increased pedaling anti-squat, but incorrectly interpreted the sensations as reduced efficiency. Just a guess, though, and I wouldn't dismiss his observations because they don't line up with the theoretical interpretations - that's the opposite of how science works!
  • 1 0
 @R-M-R: If you look at the Kinematics on that frame (Canfield design) and the location of the main pivot (Instant center) it's designed to be used with a 32 chainring. Smaller than that and chain torque causes the suspension to compress (squat) which is a bad thing for climbing loose dirt as anybody who's ridden a horst link bike knows. A little bit of anit-squat to drive the tire into the ground is a good think in my opinion but not so much as to completely lock out the suspension.
  • 1 0
 @R-M-R: I have personally built myself bikes with ~150% antisquat just to see what it was like and haven't been able to actually produce pedal jack that I can perceive.

I do remember it from some 90s bikes in the granny, though. Maybe I should fire up linkage, find some old photos, and see if I can figure out what kind of values those things were at.
  • 2 0
 @Henchman21: Canfield's designs have changed over the years and are tuned for each client. His latest "perfect" design was imperfect according to his last design. No design is perfect and altering the properties of one design often just bring it closer to the properties of another - both of which claim to be perfect. I'm more honest with my clients and help them understand the trade-offs inherent to whatever properties they choose. And regarding Horst bikes, models currently on the market range from about 60% to over 150% pedaling anti-squat, so the feeling you describe is not intrinsic to Horst designs, it's just the choice of the designer of whatever Horst bike you rode (probably a Specialized, which used to use lower than average pedaling anti-squat).

@waltworks: Yeah, my long-travel bike has over 150% in its current configuration, in the sprocket combination I use for my models. Very stable and firm under power, though with the associated high level of pedal tug when pedaling through rough terrain.

In the triple chainring era, there were bikes with over 200% AS in the little ring. The most extreme one I rode was an ancient Cannondale that definitely exhibited jack, and it was far from the worst that made it to market. Did you ever ride a GT RTS? That was one of the most extreme - certainly among mainstream bikes.
  • 1 0
 @R-M-R: Never rode an RTS for long enough to form an impression but wasn't the pivot *under* the bb or something like that, with a link that took the wheel on a somewhat rearward path? I could see that doing some really weird stuff...
  • 1 0
 @waltworks: It was just inverted from what we would now consider normal - like a new Norco Range, without the idler. Super high pivot and a linkage near the BB.
  • 17 2
 Recently swapped a set of 175mm for 165mm primarily to try and get a bit more ground clearance.

Don’t know about efficiency but I could feel the difference at full leg extension and had to raise my dropper post, which at full extension was now too low

I wouldn’t have though 10mm would have made such a difference….which is also what the actress said to the Bishop
  • 12 6
 You mean Raise your dropper post, not lower it. Shorter cranks mean you have to raise your post by the same amount.
  • 5 0
 I went from 170 to 165 recently, and also simultaneously slammed my cleats back. Didn't touch my saddle height. Think the cleats did enough to compensate. Pedaling feels like i use slightly different muscles. Additional clearance is noticeable. Cleat slam is very noticeable on jumps.
  • 2 0
 @Jvhowube: by slamming them back, you might save your achilles also
  • 5 0
 @Endurahbrah: that's basically what he said
  • 3 0
 @Jvhowube: yeah I recently went to 165 from 170 on my privateer and also noticed the slightly different muscle groups being worked, I don't know if I'd go less than 165 since where I live is mostly winch and plummet, and I do notice the slightly less leverage on the pedals in certain parts. Got a smoking deal on the e13 Helix Alloy I couldn't pass on and the smallest size they have right now is 165. I didn't downsize my chain ring though.
  • 2 0
 @poleczechy: go smaller on the cranks and decrease the chainring size, and after a few minutes of pedaling you'll forget about it on the climb (unless you drop like 20mm in one go, in which case it might take a few rides, and might make slightly different muscle groups sore for a bit. At least that was my experience going from 165>145)
  • 10 0
 It seems the overall result is: If you have pain, they may be helpful. If you need more ground clearance, they will be helpful. If you're a spinner, not a masher, they're helpful. If you don't have those issues, you don't need it.
  • 7 0
 Almost everyone can use more ground clearance. Trails have obstacles, the more often you can keep pedaling over them, the better.
  • 3 0
 I feel like when doing long touring kind of mountainbiking, the long cranks are beneficial. It's fire road climbs most of the time. But on my enduro bike, I sure prefer the 165!
  • 1 0
 @WoS: Ok, but why? You have gears for force multiplication. Are you always in your granny gear? Even if yes, the benefits of less leg extension/flexion and associate joint stresses might actually outweigh the slight loss in maximum force to the wheel.

If your body can create a higher average power for a longer time, isn't that better than marginally increasing the maximum possible force, especially for something like touring/trekking/bikepacking?
  • 5 4
 @justinfoil: well, compared to 175 mm cranks, on 165 you need to either push the pedals 6% harder or spin 6% faster, to generate the same power output.
On the long run, I cannot imagine how this could be more efficient.
  • 2 0
 @WoS: well perhaps read one of the many studies on the subject rather than just imagining. It does vary a bit from person but you are more likely to get either no change or a slight increase in power rathrr than a drop if you are of average height and drop to a 165mm crank
  • 2 0
 @WoS: yup. And it's way easier to spin 6% faster with shorter cranks, and that's what gears are for. Look up "over-square" in the context of piston engines.

And if you go the power route, then it's 6% more power for a 6% shorter stroke (or is it 12% because circles and radii?). Each leg might push slightly harder, but it doesn't push as far each time. Power is force by mass by distance. Power "efficiency" doesn't care how the factors are distributed, just that the total is the same in and out.
  • 3 1
 @WoS: "on the long run"... that theory applies to road bikes or mild spandex XC terrain but for real mountain biking not so much.
  • 3 0
 @WoS: "spin 6% faster" is only cause we're used to looking at RPM. If you look at foot speed (which I'd argue is what matters more) then spinning 6% faster on 6% shorter cranks is actually the same foot speed. You're doing more rotations per minute, but each one is smaller.
  • 10 0
 Anecdotal: I was experiencing hip pain and discomfort with 175mm cranks and the pain lessened with 170mm cranks. I'm now on 165mm and the hip pain has almost gone away entirely. Pedaling feels exactly the same
  • 4 0
 Probably not anecdotal. Your knee won't be swinging out at the top of the stroke and rotating your hip. Or at least this was what happened with me. Went from 172.5 to 165 on my road bike and now living the dream.
  • 1 0
 Same here, only on the right hip, and it was enough to switch from 170 to 165 to decrease the problem. I would have gone to 160, I am 172 cm, but there is not much available.
  • 2 0
 But how tall are you?
  • 2 0
 @DC1988: 5'11 ish 181cm ish
  • 4 0
 Same here. Was using 175mm cranks because I'm 6' tall and all the big bikes come with 175mm. Went in for a bike fit for my cx bike and was fit for 165mm. Total game changer. No knee pain. No hip pain. MORE power for less perceived effort (per Wahoo Kickr and Zwift). Didn't think to change my mtb cranks until this summer and they made a huge difference, especially wrt pedal strikes.
  • 14 4
 Cool so just ride whatevers on my bike, unless i need a bigger or shorter dropper post and i already have axs or something
  • 26 1
 No wait that doesn't involve money or trends. Just who do you think you are?
  • 2 0
 @howsyourdad: his stack is probably too low and chain stays are too short so he doesn't even notice his cranks are too long. s/
  • 8 1
 I'm 198cm and will stick with 175s. I tried 170s and they felt fine, power output felt the same but that little difference in distance was enough to cause distinct knee pain that I couldn't alleviate any other way. Cleats all the way back with 175mm cranks has so far created the most comfortable outcome. I'm glad I tried 170s and if I build a DH-specific bike I'll use them. For pedalling the 175s feel better. I've been riding 175s on low BB bikes for a long time and don't suffer unduly from pedal strikes.
  • 3 1
 @Bro-LanDog:
I'm similar, I thought about trying shorter than my current 175's but I don't currently have issues so have stuck with what I've got.
  • 4 0
 I'm 2m and was used to 180s, since that was the biggest size regularly available.
When I built my latest bike I accidentally ordered 175s and to my surprise I loved them almost right away.

They felt really smooth/efficient and more comfortable.
I might try out even shorter cranks.
  • 3 0
 I’m in the same boat as you. I built up a new MTB earlier this season with 170mm cranks, but after three rides swapped the crank to a 175mm version. I think part of the issue is I have 9 other bikes, all with 175mm cranks, so switching on one bike simply feels weird. If I go shorter, I’m going to need to do it on all my bikes, not just one.
  • 7 0
 Same here, as a tall rider I switched back to 175. When going from 175 to 165 f.e. not only do you have to raise the saddle height, but Handlebar needs to follow to keep the same distance. This also was not mentioned in the article, he just switched cranks, raised saddle, but then just dealt with the higher difference from saddle to bar?
  • 6 0
 @dogdaysunrise: Shorter cranks highlight the poorer saddle to stack height delta compared to smaller sizes. I get jealous of seeing people riding Medium frames with their saddle being level with their 20mm rise bars. I have a Canyon Spectral 29 XL with a 50mm riser and it's still lower than my saddle at max extension!
  • 3 0
 I'm 6 ft 5 in tall and so far I prefer either 175 or 180 cranks. This is just based on how they feel when I'm pedaling. 180 cranks just feel right for my 36-in inseam. I can ride shorter cranks and they feel okay, and I can get used to them, but compared to 180, shorter cranks give me a little bit of that feeling of riding a kid's bike. And once I get used to a crank length, switching to any other length causes some knee discomfort for a few rides. And I just want to concur with a comment here that shorter cranks accentuate the shorter stack and shorter seat tubes on modern frames. My seat post is already up in the clouds and I already need to run riser bars. Shorter cranks will cause me to need to adjust those things even more. And my bike will look even goofier than it already does. Modern geometry is not yet great for the taller riders.
  • 4 0
 I’m 196cm and I’ve found the same thing as you with a preference for longer cranks. The lowest I can comfortably go on road and mtb is 175mm as they feel awkward below that length. I still prefer 180mm if I can find them but I’ve settled on 175mm for mtb primarily because I love the stiffness of eewings and the longest is 175mm.

Also, there seems to be an assumption that shorter cranks are easier on your joints. For some people I’m sure it is true but that’s certainly not true for everyone. My body prefers the greater range of motion of longer cranks for maximum comfort and power output. I’m sure there’s a limit to this but I haven’t found it with 180mm cranks.

For tech descending, the wider fore/aft base created by longer cranks is also a benefit for me. With shorter cranks like 160mm, I feel that I can get pitched over the bars more easily on steep, rough downhills. Think of it this way, the base of the triangle formed by your legs and cranks is bigger with longer cranks and your center of mass is therefore slightly lower.
  • 1 0
 @Scnelson1: at 5"11 I like 165. I don't mind 175 other than rock strikes. I don't like 145. I'd probably still be fine on 160 or what not.

I highly suspect 175 are too much for the average rider but going super small is just as bad as going too long. it's also preference anyway. another pro of 175s.. they're cheaper lol
  • 2 0
 @bogey: I’m 195cm and my e-bike came with 160 cranks. I think I agree with you that on steep trails I feel like I’m more over the bars. But I only have like 10 rides on the bike so I need more time to see how it feels. Might go to 165 cranks
  • 1 0
 @Scnelson1: Exactly, exactly how I feel and no word about stack in the article or about the issue that you and me have the seatpost already way, way up.
  • 1 0
 Just to update. I don't think I was right about this. I've gone back and forth now between 175 and 170 and I actually prefer 170 now, which is a surprise. 175s now feel like I'm pedalling squares and the ground clearance difference is noticeable. I'm even going to try 165s for the sake of science. Part of this realization came as this article came out suggesting that the reason everyone likes short cranks now is because of steep seat angles: we don't want to back of the stroke so far behind us. This makes sense if you think about it. There is an optimum position for the back of the stroke relative to our hip center. If the hip center comes forward so does the back of the pedal stroke and the only way for that to happen is to shorten the crank. I'm going to try 165s and see if that's true for me.

nsmb.com/articles/the-backfoot
  • 1 0
 @alexsin: How about downhill performance? Are longer cranks better for stability on steep descents? Do shorter cranks provide better maneuverability? I wonder what the balance is
  • 11 0
 Pick a crank length and be a dick about it.
  • 19 0
 Pick a dick length and be cranky about it.
  • 18 0
 Pick up your dick and crank it
  • 1 0
 Si, mi amigo!
  • 7 0
 Worth noting that the reason we're even having this discussion is that dropper posts exist.

Short cranks and higher saddle are horrible if you're on a rigid post, it's like having an anti-dropper for the descents. Back in the day 170/175 (which are pretty much indistinguishable to most people) became the standard because it generally gave folks enough room to move their butts around when going downhill.
  • 6 0
 I believe the majority of the riders here are downhill enthusiasts, I would like an article on how the length of the cranks can affect downhill riding. I am 191 cm and I like longer cranks , downhill, I feel more stable and better control, actually even with wider stance some sort of spacer between the crank and the pedal Smile . What do you think?
  • 1 4
 The only advantage for DH is the pedal clearance, you are correct.
  • 1 0
 @DoubleCrownAddict: actually (maybe depending on flexibility) I've found that the short cranks are a benefit for me. I used to get a 'hip pinch' in the forward foot's hip when taking heavy compressions. Basically I was reaching the end of my hips range of motion with the forward foot. With shorter cranks, I have more ROM and the 'hip pinch' doesn't happen as often or as severely.
  • 1 0
 @sdurant12: Ok, they are less stressful on hips. I was thinking in terms of bike handling, where I think the shorter cranks are a disadvantage.
Good riders can use their cranks for leverage to get more traction on the ground or to help maneuver the bike in the air. With shorter cranks you lose some of the leverage of controlling the bike.
  • 5 0
 I'm curous about the cadence affect, power is a result of torque and rpm, shorter arms reduce torque at the cranks, the 2T smaller ring brings it back up at the rear wheel but to move at the same speed the cranks then have to move quicker, 10mm crank length and 2T off the chainring is approx 6-7% so if you normally spin at 80rpm you will have to increase to 85rpm to get the same power, most of us match our gear by cadance so if we try and stick to the same cadance we might end up either going slower or dropping to a faster harder gear, do you just have to accept and get used to a high cadance with shorter cranks? and is that maybe a helpful thing as i suspect compared to efficiancy tests and road riders we mountain bikers usually chug along at lower cadance out of the trails.
  • 2 0
 Same Q here. I had a bike with 165mm couple years ago, always used to 175mm (6.3"), and I never became friends with it. It felt like I was always in the wrong gear, felt weak, rythm was off. One of my bikes now runs 170mm, not as much of an issue there. Feels ok.

I suck at high cadence, and rarely go above 80rpm other than in bursts, even on dropbar bikes. Probably a lot due to habit/muscle memory. Higher cadence also means higher HR for me.

Disclaimer: rolling gnar here, no big mountains, always ride for at least a couple of hours.
  • 2 2
 Put simply: you'll get used to it.

Yes, it's easier to spin higher cadences with shorter cranks, given that your leg/foot has less distance to travel, thus foot velocity is decreased for a given RPM, making it easier to change pedal stroke directions smoothly. However, skip the chainring size decrease. It greatly reduces roll-out, the distance a stroke moves you. If the small force reduction bothers you, you'll just find yourself in a slightly lower gear and able to spin a higher cadence there. If you're already stuck in the granny, the force reduction isn't going to be make or break a climb, since you're not putting max force down all the time, you're doing traction control constantly. And the less foot distance per stroke means it's going to feel easier to get "over-the-top" and back into the power stroke.

Think about when 29ers: longer wheel radius made the same change between forces at the pedals and wheel. But bikes are still specced with 32t cranks. Same with SRAM's 52t Eagle update: still 32t chainrings, not some industry wide switch to 34t.
  • 2 0
 @justinfoil: That's a good point about foot velocity, so you might be going at a high cadance but it might not feel too fast as your foot is moving at the same speed as with a longer crank at a lower cadance.

I'm not too sure what you're on about with chainring size though, i used to run 34-36t on 26" wheels and bikes would come with double rings with big chainrings, now on a 29er i run a 30t and wouldn't even try and run a 34 or bigger on it, Bike brand specs have been slower to drop as low as 30t on 29ers but that's largely down to big cassettes having come around at a similar time to 29er popularity, giving you that lower gear without a smaller chainring.
  • 1 0
 @maglor: I run several bikes, 28t on the fatbike, 30t on the trailbike(s), 34t on the downcountry and 48 on the gravelrig. Different crank arms on these too.

Going from 32t stock to 34t on the DC/XC bike was actually an issue. I needed more top end, but it messed up the suspension settings. More bob, so I had to reset everything.
  • 1 0
 @maglor EXACTLY this!!

All these 'shorter' is better seem to focus on the rider 'feel' of force on the pedal - use a "smaller chain ring" "choose a lower gear" all equates to LOWER SPEED.

What never gets mentioned, some people area already on small chainrings, in the lowest gear, at their max cadence.
Slap on a shorter crank and they are going to have a rough time 'getting it up' !
And then there are those of us that actually enjoy(?love/hate?) climbing to 'earn their turns' and to end up doing them slower or with more effort (ie. the +5-7% req'd per -5mm) may not be worth the minimal gains, I seem to 'still' smack my pedals/cranks as much as ever.
Even with a decent FTP (4.1w/kg) I can certainly feel the extra effort req'd
  • 1 0
 I don't know if you've read any of the studies? I did a while back because i wanted to try shorter cranks on my enduro bike and the only option available at the time for 160s was 5dev. So i wanted it to be an informed decision before i dropped $500 on a pair of cranks. The gist is the crank is, in my case, 10mm shorter, which means you raise your seat 10mm. By raising the seat 10mm your leg is straighter when you are pushing down on the pedal. Basically the power you lose by going to a shorter crank you gain back by having your leg be straighter. Im in CO so all big, steep, chunky long climbs and in my experience the cranks being shorter helped pedal strikes a ton and i noticed the smaller circle but did not notice a loss in "power". I did not go down on the front sprocket, still on a 32. It took a ride or two to really get used to them as ive been on 170s for almost 2 decades. But after 2-3 rides i was PR'ing all my local climbs. I'd never go back.
  • 5 0
 I didn't see any mention of foot/shoe size and I think this is a big miss.

I am tall (198cm) but also have big feet (size 15. 5/euro 51 plus or minus depending on makes).

Other guys tall guys/gals height might be rocking smaller feet, two or 3 sizes smaller which could amount to 10s of mm (sure its not straight down but must factor in somehow)

Anyways, this sasquatch who loves his 180mm cranks thinks it's a miss in the discussion.
  • 1 1
 With proper pedaling technique foot length shouldn't be a factor.
uesca.com/want-more-power-on-the-bike-start-with-your-ankles
  • 2 0
 I'm right there with you at 2.05m tall. Any of the leg length / crank length calculators still put me solidly on 180mm cranks, which is what always makes my ankles, knees, and hips happiest.

And even being the oddball that likes ~50mm saddle to bar drop on my MTB, I wouldn't want to raise my bars up higher to maintain my fitment with a correspondingly higher seat position due to shorter cranks.
  • 5 0
 I think the impact of seat height is not getting talked about enough. I am 192 cm and constantly try to lower seat height on all my bikes by tweaking cleat position, low stack shoes/pedals, and running longer cranks. Getting your body lower on the bike when pedaling improves traction, aerodynamics, comfort (saddle to bar drop), and prevents the imbalance (fore/aft) many tall riders experience. When your seat goes up your ass goes backwards meaning more strain on your back to maintain traction and steering on climbs. Agreed if you are 6 ft and below you may want a shorter crank. 175 mm seems to be the sweet spot for me despite the pedal strikes.
  • 5 0
 BICYCLE CRANKS,
Seven Inches is the Length Used for Road Riding..
"What length should cranks be?" is a question that agitates a great many riders who secure a new mount each year, mainly to keep abreast of the times. In the majority of cases the final decision is left to the agent or salesman. Accordingly more seven-inch cranks are in use this year than any other length, because the greater number of riders who discriminate have settled upon this as the most suitable length for road riding. A few cyclists, who must be classed as extremists, employ seven and a half-inch cranks, and a few who are blessed with particularly long legs ride eight-inch cranks with a correspondingly high gear. On the race track all lengths of cranks are used, but the preference continues, as it has for many years, in favor of the size and a half inch length. Vice Consul H. B. Fullerton believes that six and a half inches is the proper length for road riding, and argues that a longer crank requires an unnatural motion and calls into play muscles that have never been developed in any other sport than cycling. One argument in favor of a longer crank is the ease in back pedalling.

BICYCLE CRANKS - The Buffalo Commercial - Buffalo, New York · Friday, August 25, 1899

www.newspapers.com/article/the-buffalo-commercial-bicycle-cranks/131372620

7" = 178mm, 1899 = "safety" bikes, single speed, fixed, coaster or rim brake
  • 1 0
 Love this, nice find. >;D
  • 5 1
 I (196cm) tried a few lengths of cranks on my drop bar bike a bunch of years ago, trying 175, 170, 172.5, and 180. I did NOT like the shorter cranks, even after a few weeks of getting used to it. Eventually I settled on 180s for that bike. I've got 175s on my mountain bike now, and I'll probably keep those for a while, unless I get a screaming deal to try something different.
  • 3 20
flag BurtMcBurburt (Sep 6, 2023 at 6:41) (Below Threshold)
 193cm... Shortest I've tried is 170, also settled on 180. Mostly to reduce saddle height, but also for sustained climbs. It looks like Tweed Valley's tallest climb is 1000m or so, and I'm guessing long climbs aren't ride of choice for Cathro.

Horses for courses, also why ya'll pedaling through chunk anyway... just hold the cranks level & keep your heels low, get with the program.
  • 12 0
 @BurtMcBurburt:
"also why ya'll pedaling through chunk anyway... just hold the cranks level & keep your heels low, get with the program".

...Not sure that works for climbing.
  • 3 0
 I'm 198. I have 180s with an oval chainring that I really like on my hardtail but that combination does not work for me on any of my FS bikes - on those I stick with 175s and a round 32t ring. I recently put some time on 170s and while efficiency wise they felt fine, ground strikes weren't lessened appreciably and I started getting some knee pain which went away when I switched back to 175s. So I'm staying put on 175s.
  • 2 0
 I'm 6' tall. Obviously have ran 175s like everyone forever, but switched to 170's on my Transition Patrol a few years ago. Very noticeable, but I was like "meh" and ran them. Been 4 years now and going back I can tell that 175's are a bit more comfortable. My buddy who is 5'8" went to 165's and it was distracting to ride his bike, but he loves them.
  • 1 0
 @alexsin: Yeah, I think there's more to this. It's a great article, but further studies should include measuring the riders carefully as well, and putting them in categories accordingly. Hip to knee, knee to ankle, ankle to toe, as well as torso and arm measurements, preferred reach, etc. That's maybe overkill, and an individual test such as you and Seb did is the only way to find out what works for you and whatever bike you're riding.
  • 4 0
 @BurtMcBurburt: I tried holding the cranks level and getting my heels low, but somehow that doesn't propel me uphill through chunky terrain. Please tell me how you do this.
  • 1 0
 196 or 6'5 and I found 175s I was losing power on my downstroke because of a hip angle that just felt like a dead zone to me at the top of the pedal arc. Felt I had to use more effort to get the power started vs a consistent push. In 2019 a new bike came with 170s and I feel like that dead zone is gone and they're more comfortable for me and no drawbacks. Have kept 170s on my bikes since then.
  • 4 0
 You have to be careful using science to make equipment decisions. The problem isn't correctness - the problem is other cyclists. There's a small mountain of scientific evidence that flat pedals have the same efficiency (and most of the time lower system weight too) as clipless pedals. But if you slap some flats on your road bike, you're going to catch a LOT of (wildly incorrect) lectures from roadies. Ask me how I know.

Short cranks seem to be safe because no one can tell you're running them. I'm 6'2" and I put short cranks on my bike three years ago and I haven't been pulled over to catch a lecture about long cranks and power transfer (yet). With flats, it's absolutely constant.
  • 2 0
 Spot on, I've been ridiculed before just turning up at work on flats before
  • 3 0
 It's great to see the norm of 170-175mm cranks being questioned in the media. They get specced on all sizes of bikes because it's easy for companies to do.

Moral of the story is that everyone has a usable range of crank length depending on their application and terrain. For mountain bikers, generally shorter is better because pedal clearance is better while pedalling power and efficiency isn't effected negatively too much (or not at all) and can be compensated for with adjustments to you bike.

The big benefit is for short riders forced to ride 170-175 when they buy a bike. There are a lot of benefits to 150-160cm cranks for riders shorter than 5'8" to fit their biomechanics, resist injury and increase performance, not just reduce pedal strikes.
  • 2 0
 Don't get me started on kid's bikes specced with 165 mm cranks omg.
  • 2 0
 @fabwizard: Kids need lots of leverage to push around bikes that weigh 75% of their body weight
  • 2 0
 @VtVolk: that seems to be the theory huh.

Child centric brands seem to mostly have their poop together on crank size. Spawn, Vpace etc.... But big brand just put big cranks on no matter the rider size. Absolutely stupid.
  • 4 0
 I thought the biggest news of the GX Transmission release was that the cranks came in 170mm, 165mm, and 160mm. Running 165mm eeWings with a 30T ring on my Tallboy here in Park City and I looooooooove it.
  • 1 0
 How tall are you and what size is your bike?
  • 2 0
 @HappyBiker19: 6ft, large frame
  • 4 0
 I tried 165 cranks earlier this year and ended up not really liking it, although I'm not sure why. I may try them again in the future, but I settled on 170s for now. I used to only run 175.
  • 3 0
 @sebstott thanks for talking about the need to raise the saddle for proper leg extension. Can you comment on if you also raise your bars? When I ride with shorter cranks the saddle to bar drop is pretty extreme, raising my bars for a comfortable seated position usually results in my bars being too high for my standing position.
  • 4 1
 Good point! Your standing height is also going to increase by around 4mm after moving from 175mm to 155mm cranks as well.
  • 1 2
 You don't need to raise your seat the same as the crank length reduction. The top of the stroke is already lower, reducing leg flex even without raising the saddle. Try going halfway, split the different between less extension at the bottom and less flex at the top. Try the same half-change for the bars, although as has been pointed out, your standing "height" will come up with shorter cranks, so raising the bars 10mm will only bring the effective height when standing up by 5-6mm, and with a 10mm saddle raise, you're even when seated. I ended up raising my saddle only 5mm for a 10mm shorter crank, and my bars 2.5 mm (already had the spacer for Shotgun Seat clearance against my stem). Means the bars felt pretty much exactly the same when standing, and only 2.5mm lower when seated. When combined with less leg flex through the whole stroke, the bars feel higher anyway since you don't get folded up as much: knees stay further from chest, feels more upright/open.
  • 3 0
 One thing to note about the dropper post issue is that if you have an adjustable post with shims (like a OneUp), you might be able to get more drop with short cranks. I went to 165 cranks on my Dreadnought and it was great. I got more ground clearance, was able to get 10mm more drop from my post, and overall felt like the bike fit was better (I have short legs for my height). I’d be curious to try a 160 or 155 crank in the future.
  • 3 0
 The biggest thing I agree with on this article is 175 cranks being the default is silly. I'm 5"'11" ride an YT Jeffsy XL frame and run Canfield150 cranks with a 30T oval. I first tried them on a Polygon D7 size L when the pedal strikes were ridiculous and the dropper was too high, the new cranks fixed all of that. I rode the Jeffsy for 2 weeks with the stock 175 cranks and round ring, pedal strikes galore, pedal stroke felt all "lopey" and the XL felt a tad too big. Once I swapped in the 150 cranks all was well and the extra size melted away.
  • 1 0
 100% agree.
  • 3 0
 At 6'4, I've been a huge fan of 145mm cranks on my enduro bike for winch and plummet riding and bike park. I don't feel like I lose anything on the climbs for that style of riding (and I'm pretty picky about climbing efficiency). And it lets me get away with a very low bottom bracket (I mulleted my bike but didn't do anything to raise the BB back up, and I actually lowered the fork a touch to keep the head angle reasonable) which has noticeable advantages when descending imo.
  • 1 0
 That is really surprising but it just goes to show how different things work for different people.
  • 3 0
 Recently changed from 170mm to 152mm cranks and I'm 181cm tall. I wanted less pedal strikes as I have an XL enduro bike (long wheels means low breakover angle). I have only a couple of rides on this setup but I see no downsides. On the initial ride I felt like the pedals spun up a little faster on short steep climbs but everything else felt pretty normal.
  • 4 0
 Now it's time to try wider cranks, nobody seems to be looking at stance width and all MTB cranks are 170ish Q factor. Really want to try some 220mm width cranks with 155mm arms
  • 1 0
 +1, I would love a wider Q, it's blasphemy that nobody makes cranks that can adjust that.
  • 3 0
 @DoubleCrownAddict: the article is a good reminder of how to pedal but has nothing about height, leg length or foot size. Maybe the argument is shorter cranks are better for bigfeets so the heel can drop further and vice versa. I don't see how (anecdotally) that it's a non-factor. A lot of ink is spilled over cleat/foot positioning. Now more ink about height but I don't think it can be ignored. Would love to see a study on it.
  • 4 0
 I went from 175 to 165 and hated it. I couldn't sprint at all - I sold them after a few rides and went to 170 and have found that a happy medium. Shorter isn't always better for sure.
  • 1 0
 I haven't tried 165 but 170 feels better than 175 to me at 6'2"
  • 1 0
 Did you size your chainring down or no? Just curious.
  • 1 0
 @iduckett: I went from 32 to 30. Honestly it was awful
  • 1 0
 Same. I learned on 175s, tested both 170s and 165s and really disliked 165s on my pedal bike and consistently was missing my explosive climbing abilities, although my e-bike has 165s and it's fine.
170s however are really quite nice for the pedal bike for me at 5'11" with longish legs.
The extra height on the bike is a real concern with short cranks as you are throwing off the entire geo really.
It's odd to me that some people can't even feel a difference in crank lengths.
  • 3 0
 This is a cool article. Not being a tall person myself, been happy with 165mm cranks for a long time. Kind of an off the wall question, I wonder if there are any riders out there who run mixed crank sizes due to previous injuries or body composition.
  • 3 0
 I can't think of an imbalance that would favour one crank reaching both higher and lower than the other, though I suppose it's possible. I do know of riders using insoles to raise or lower one leg, different cleat placements to move one foot fore or aft, and cleat placements or axles to create asymmetric stance width.
  • 2 0
 @R-M-R: Fun idea. I'm not an engineer or a physiologist so any idea I have is meant to be called dumb by folks in forums. Could you imagine going to a bike fitter and them telling you that you need a 170 right and 172.5 left crank?
  • 1 0
 @noodlewitnosteeze: Some unconventional ideas are unconventional because they're dumb, but some lead to interesting thought exercises. Yours was the latter!

Most bike fitters are just following a set of simple formulae based on body dimensions and flexibility measurements. It would take a more insightful process to spot whatever situation would lead to different crank lengths. Not every bike fit is ideal - I've even seen one cause a serious injury in a rider whose position was fine prior to the fit - so anyone who remains uncomfortable should continue to investigate, especially from the medical practices.
  • 3 0
 Excellent article. Thank you to Ben and Seb. I've done a fair bit of crank length (as well as many other) size experiments. The key to interpreting results like the graph shown here is the *range* of results. Just because the average of peak power output came at 20% leg length doesn't mean it will for you or for me. No one thinks of themselves as average. Yet we are quick to accept the average results. Different strokes for different folks.

A critical issue that Ben very briefly mentioned is the relationship of gearing to suspension. Shorter cranks require lower gear ratios which can negatively effect suspension. The butterfly effect of changing one bike component effecting seemingly unrelated ones is oft overlooked.
  • 2 0
 This is one thing I didn’t consider with my bike. I have a linkage driven single pivot and doesn’t seem to have affected anything much (no noticeable pedal kickback or anything). I wonder what the detriment is with something like VPP or Ibis designs where the chain is used to enhance climbing efficiency.
  • 3 0
 @iduckett: The chain interacts with climbing properties on all non-URT suspension bikes - yours, VPP, i-Drive, dw*link, Horst, single-pivot, etc.

The effect of changing chainring size is less than the spread in pedaling anti-squat between popular suspension designs, so it's unlikely the change would put any given bike outside of what we might call "normal". To put numbers to it, changing from a 32 T ring to 30 T ring typically increases the pedaling anti-squat by about 4 - 5%.
  • 4 0
 Good write up! I have 165mm cranks on my Transition Patrol and smash the cranks alllll the time, and was considering going 155m but was worried about downsides. Thanks!
  • 2 0
 I got 145mm cranks (PINND) on my ebike (2023 Orbea Wild M-Team) and I freaking love them. I would definitely put 155mm on a Patrol or even 150mm.
  • 4 2
 @PJSANAB: e bike may as well have mx foot pegs lol.

Just poking a bit of fun. All you ebikers don't get your charging cables in a twist.
  • 1 0
 I ripped the 165s off my patrol after 2 rides and went 155. That bike was unrideable in techy terrain at 165 for me. At 5'8" with a 29" inseam the 155s are absolutely perfect and I actually feel more powerful bc I'm using bigger muscles through a larger portion of the stroke.
  • 1 0
 @Nwilkes: What size chainring did you use?
  • 2 0
 @dmackyaheard: 28T. I could use a 30T but would end up in the 50T granny too often so I opted to try to do most of my pedaling in 2nd gear for better chain line.
  • 2 0
 I have 155 canfields and 26T chainring (Passquest direct mt) on my Process 153 29. I haven't had any pedal strike issues since. Downhill I have zero fear of bottoming the chainring or pedal strikes. It's been an awesome setup for an out of shape dad, albeit a lower geared one w/ the 11-48 cassette. I tried 30T, then 28T oval, but even that was too big a gear for me to push. 26T seems shamefully small, but the granny ratio considering tire height is actually the same as my old 27.5 134 w/ 30T chainring, 175 cranks, and 11-46 cogs. I don't know HTF people push 30 or 32 chainrings on 40lb 29ers. Animals. ANYWAY, I considered removing my OneUp bashguard since I maybe have hit that once and it's extra weight. All in all 155 cranks have been a great experiment, and my confidence downhill has skyrocketed between that and a full coil setup.
  • 1 0
 FTR I'm 5'9" (175cm) w/ size 11 shoes. With the lower gearing, I've kept my cadence pretty much the same, 80rpmish (my natural cadence on the trainer). I go between 175 cranks on my fatty, 170 on my gravel bike and these 155s and don't feel much of a difference in cadence. If anything the 175 cranks I am spinning a little slower, maybe 70-75rpm. They feel less natural to me now, as a result.
  • 3 1
 I personally don't like short cranks at all!!!! Not only does it feel like I'm an energizer bunny on the bike (I don't care what the science says), it just feels weird. The increased saddle height ruins my stack. And on top of everything else, I feel more stable in the attack position as the distance of my feet on the pedals is bigger. I feel less safe with short cranks, feels twitchy.
  • 4 0
 Science says 3 of 4 sources found possible gains. Science says this is called confirmation bias. In reality its all just a discussion on random fitments. Some people like twitchy, some hate it.
  • 2 0
 Maybe we can send the whole PB crew out to test this? For a longer period of time? I like the concept of the article but it hasn't really surpassed any of the thicked boxes done in previous articles posted on the matter.

It kinda stops at the.. it could be a solution for you, but...

- On the downhill, this narrow(er) stance makes it feel 'better' because you are prone to use muscles that maybe aren't beaten up from daily / regular fatigue?

- I seriously wonder if reducing in cranksize and then accordingly reducing in teeth on your chain ring will make you reach similar topspeed at your desired cadence / rpm - as everyone has their sweetspot of power output versus at a certain amount of rotations. I can understand that you can spin it up faster, but to really maintain topspeed? Or at a certain point you are doomed because you reached 'the end / max speed at x rpm' of your chainring.
  • 1 1
 In my experience the top speed is the same. Think about it as 'foot speed' and not RPM. If you go from 200mm cranks to 100mm cranks, and cut the chainring size in half, then you have the same leverage. But now you'll be pedaling at double the RPM? But that's okay, because the foot speed is the same. (Note, for such an extreme example maybe it's not okay, because something something physiology, but in my experience on cranks from 145 (enduro bike)-165 (xc bike), there's no issue once I adjusted chainring size (30t vs 34)
  • 1 0
 @sdurant12: You would get the same results (or not better) with shorter cranks and stepping down from 34T to 30? Just to get some confirmation, as it's still difficult for me to understand the whole.
  • 2 0
 Regardless of whether shorter cranks work better for a 6ft bloke or not, it did always strike me as bonkers that short cranks are typically 170mm, medium 172.5, and large 175mm when the percentage change in people's leg lengths is so much greater than that. Indeed, Bradley Wiggins broke a world record using a bike with 172.5 amd 175mm cranks and he didn't even notice the mismatch
  • 2 0
 6'3", 165s on multiple bikes idk.. feels much better? And I actually lowered my post from when I had longer cranks. My legs don't move much, my hips don't rock anymore, and I've been getting *much* faster lol. Maybe just because I'm chilling in my saddle n comfy so I ride more.

Not saying this would work for anyone else, but uh yeah I'm done wit long cranks Smile
  • 3 0
 @ 194cm I run 165mm cranks for clearance and have no qualms with power or saddle height. Would I go swap my 175mm road cranks for better efficiency? Costs money.
  • 2 0
 Same reason my Stumpy now has 160mm cranks and my Checkpoint all-road will forever have 172.5mm cranks. Spend for clearance on the trail bike, no need to spend on the graveler!
  • 3 0
 I love my hope 155 crank.. No lose of power. Actually, I am faster on a climb and after the ride, I don't have that pain on my legs anymore.
  • 1 0
 Thanks for the in-depth testing. I’d like to get a bit more detail about the type of riding you were doing, as I suspect this comes into play when deciding what cranks may work best for a specific rider.

Are you mostly climbing / descending or are you also riding longer XC / traverse type trails? My hunch is that the higher saddle and reduced leverage will have a greater [negative] impact for riders who are spending more time in the saddle over undulating terrain. I also suspect the reduced leverage might have negative impacts on acceleration for technical moves… like quick acceleration to get up / over obstacles. Would you be up for doing the same test with an XC bike on more traditional XC terrain?

I’d also like to note that some of your ‘cons’ could be addressed by designing bikes around shorter cranks. The bottom bracket could be lowered for riders who prioritize low CG over pedal clearance. And suspension designs could be adjusted to optimize for 28t rings… food for thought.
  • 4 1
 I don't understand all the talk about reduced leverage. You simply adjust gearing to get the desired leverage between foot and contact patch. What changes is the stroke length. You can either increase the gearing to get the same power output at the same frequency, or increase frequency (=cadence) to get the same power output at the same linear speed, which according to some studies is what people tend to do.
  • 2 0
 @ak-77: Am I allowed to site other publications here? ...
nsmb.com/articles/shorter-cranks-for-downhill-performance

I'm getting my information from this other in-depth article which offers some contrasting opinions to what Seb has published here. It tracks for me that swinging a bigger circle might have advantages for acceleration and technical moves. In the same way that having a stance that is closer together (more Moto) might be preferable for DH. I hope to try all this out for myself at some point. All I've done thus far is go from 175 down to 170mm cranks on my Ripmo and I do prefer the 170s on that bike. [I'm average height at 5-10 /178cm]
  • 3 0
 @basic-ti-hardtail: I immediately noticed this tester swapped cranks without also swapping chainrings and adjusting saddle height. I don't think a like for like comparison of pedaling performance can be made on such a setup.
Also the 'moto' argument can be countered with surfers IMO.
In any case I think personal preference plays a big role. The only thing independent from that pedal strikes. There is a huge parameter space when it comes to optimizing the interdependent parameters cadence, stroke length, force and linear speed. That sort of parameter space cannot be sufficiently probed with a single measurement on a group of 16, as the totally uninformative graph in this article shows.
Best thing to do is go out and try for yourself, give yourself time to adjust, and draw your own conclusions, realizing they have limited validity.
  • 3 0
 I did go from 175mm to 165mm, noticed that my hips and knees feels much better, I have less fatigue. Wheelie, manual, balance on technical terrain improved.
  • 2 0
 Wife is super short. Switching to 155s with a 28 was a game changer for her. Moving the seat 15mm up was a huge positive for leverage and got the seat above her bars for the first time ever.
  • 3 0
 What about "virtual" chainstay lengh? Some articles into the past here said it feels longer, so with the benefits without the downside of a larger WB ..
  • 2 0
 That is exactly what I felt after switching from 175 to 165. Like I need more efforts to bunnyhop and make initial into-manual movement.
  • 2 0
 @Velosexualist: You must be heavy on your back foot, then. Stance center doesn't change with crank length reduction: front foot gets closer to the rear axle the same amount that the rear foot moves away. Will not change the effective/virtual chainstay length if you're balanced over the BB.
  • 1 0
 TLDR my response; All points are valid although first point in second paragraph proposes the also valid point that to maintain momentum uphill takes more effort as well since the rotation is increased no-matter chainring size(32t is for 175mm btw). The third positive of the pros list is an aspect of this; less about force and more torque related as your stroke gives less propulsion, again being detrimental to riding hills. All this means is that for hardtail/XC freaks and all-terrain adventurers that's a large portion cut off of your fun. What was well spotted by Seb though is that long cranks give more leg burn on long descents so I'll stick with short ones with this primary reason, and the rest is relatable as well.
  • 1 0
 "less about force and more torque related as your stroke gives less propulsion"

Torque is a force, can't be more or less about either.

If the gearing is the same, "your stroke" will give the exact same propulsion, it's just that your foot travels less distance during that stroke. You'll need marginally more force into the pedal to get the same force at the wheel, but the distance travelled is the same. If you reduce your chainring, you reduce the distance moved, and by much more than the needed increase in force.
  • 1 0
 @justinfoil: it very well may be, if you catch the phrasing and the actual point in the positives as well you see I mean it's a more direct delivery of input between a whole rotation rather than a smooth DC-type input -- all the while the opposite is true for your muscles for uphill(you guessed it, maintaining momentum). The bicycle is just a machine, think of your own mechanics.
Also please no one ever come to me with high school or university science again it's getting boring. Just putting this out to the universe
  • 2 1
 Good article, nice broad review, but are you going to stay on the 155mm cranks?

I've been riding short cranks for many years, started riding short cranks on mountain unis (muni) and continued the trend with mountain bikes. On muni, my fav length was 150mm, but for mountain biking I run 155-165 depending on the bike.

I'm 6'/33" inseam, I ride lots of tech and do big climbs, most of my riding is in the mountains of Utah and Nevada.
  • 1 0
 I’m 2 rides in on some hope 155mm cranks from 165mm riding a medium kenevo ebike , I’m 5.10.5 ! I’d bent the previous ones so thought I’d try the shorter as heard good things about them .
Bike feels more stable , nice and tight , no more pedal strikes and don’t need the leverage with the ebike so very happy !
  • 1 0
 I'm Seb's height. Always thought I needed at least 175mm cranks. I was worried about the shorter cranks when I got a Spire (Which I think they stocked because of the low BB) but after a couple rides I didn't even notice it anymore.
  • 1 0
 The cornering thing secondary to shorter stance is more noticeable to shorter people because they naturally have shorter limbs and less leg "travel." Similar to why it makes sense for smaller frames to have higher stacks/riser bars because again shorter people tend to have less arm "travel." Both of the above allow easier flexibility in maneuvering the bike.
  • 1 0
 This is where the low BB + deep dropper insertion designs (e.g. Transition Patrol) have a huge leg up. You can fit at least a 210mm dropper on almost every size, so you get all the benefits of low BB and short cranks, while still being able to lower your saddle and hips (your center of gravity) for maximum range of motion. If I tried 15mm shorter cranks on most bikes, I'd have to raise my seat height 15mm but may not have enough insertion for a longer dropper. So I lose that vertical range of motion on the bike (raised center of gravity), which would be a disadvantage on steeps.
  • 1 0
 I don't know if short cranks "work" (as well?) for tall riders, but in my experience as a vertically challenged rider they have performed admirably. I find them supremely comfortable and I am able to spin up to speed faster. They additionally helped me clean 95% of the janky climbs that I'd get stuck on in the past.
  • 1 0
 All this time we've been messing with bar height/ stem length. I certainly like the idea of less pedal strikes, currently running 175 at 5.8". Not sure I like the idea of messing with my gearing however; -one other slight negative might be more chainslap with a smaller front chainring.
  • 1 0
 199cm here and changed out to 155mm cranks a while back and have had no negatives. Climbing technical trails is now enjoyable without pedal strikes, and stability going down is a bit better. Had to raise my seat a tad, but that’s fine by me. It’s easy to get sold on the hype but with bottom bracket heights being as low as they are now, they’re definitely worth a look.
  • 1 1
 You don’t think having feet closer together reduces base stability when going down steep stuff? Having feet further also lowers your CoG a touch
  • 1 0
 @Tustinite: perhaps, but it’s a more similar feeling to riding a motocross bike where you have pegs. The biggest difference is the pedal clearance which is well worth it for climbing on the shore
  • 1 0
 I went to a shorter crank (170 from 175) when swapping to a frame with a 10mm higher BB height. The bike felt tippy pedaling and felt noticeably higher overall especially in corners. I would think that if there is a trend toward shorter cranks there would also be trend to lower the BB drop.
  • 5 0
 Shorter cranks are terrible on single speeds
  • 1 0
 I have a relatively short inseam and from my point of view, a shorter crank will make it easier for me to fit some frames where the dropper is just that 10mm or so too long despite my overall height being correct according to the manufactures. Shorten the cranks instead of swapping the dropper.
  • 1 0
 One thing not mentioned is that a high cadence on rough ground does not work well at all. The rider will start bouncing a lot. A cadence of 70 or so works better for my riding on the rocky trails where I’m pedalling. If it’s nice and smooth a higher cadence is fine. I would think that shorter cranks would be less effective, less efficient in those circumstances. The studies I’ve seen seem to be road oriented and somewhat inconclusive. I read some that used non cyclists and low cadences were more efficient but they only tested for endurance or steady state riding. Other tests found trained cyclists were most efficient with the crank length that they were used to.
  • 1 0
 So just move into a lower gear and that will slow your cadence
  • 1 0
 @Dogl0rd: higher gear? Sure. But then you’re pushing a harder gear with less leverage. Maybe it doesn’t matter. I don’t know. But that’s what people are suggesting with shorter cranks. Lower gearing and spin faster.
  • 1 0
 I put in an order for Hope Evo cranks this weekend, wanted 155mm ones. They said end of September stock returns but they have 165s in stock ready to go, so just got some of them as I'm currently running 165s anyways. Looking like the dude in the shop lied about stock as I've no dispatch notifications. Tempted to change my order to 155s and just wait till the end of the month after this article!
  • 1 0
 Or cancel and get Canfields! Seems like they’re always in stock. Need direct mount chainring though.
  • 3 0
 @iduckett: I got an email like 10mins after this comment and my cranks are coming tomorrow. I like the Canfield stuff but Hope are like 10 miles from my house so I gotta rep the local brand > anything.
  • 1 0
 @curtiscycles: Totally! Hopes look awesome!
  • 1 0
 One thing I do wonder is that our squat strength reduces as we go deeper into the squat, to improve the range you have to squat lighter weights deeper and slowly increase.
By shortening the crank, you're not using the "extremes" of your motion you used on the 175mm cranks, therefore you always have nearer peak power available. Over time as your range of motion has decreased the ends of the stroke will weaken. Therefore short term short cranks help as you can always squat more when it's not as deep.
So if we trained on a spin bike with cranks 10mm longer than our actual bike we'd gain in the same way, maybe then 175mm cranks are better than 150mm?
I prefer shorter cranks for clearance, but my bike came with fancy carbon cranks I won't pay to upgrade unless they failed
  • 1 0
 If I was a car engine, I'd be a BL 1275CC A-series. Long stroke, and if RPMs go high, the piston (leg) speed gets too high, and kaboom. But torque at low RPM is rather good, because that's what they tuned'em for.

Modern engines are, of course, all short stroke because they learned how to make them breathe better.

You trendsetters all need bigger lungs for those RPMs!
  • 1 0
 Leg speed at high RPM is lower if you use short cranks...
  • 1 0
 @ak-77: yes, just poking a bit of fun. I suck at high RPM, no matter crank length or leg speed.

Never mind the science, I think our bodies adapt. I currently alternate between 4 bikes with different crank lengths already. All good. So I don't plan on going amok on crank changing any time soon - I'd rather upgrade something else.
  • 2 1
 Ive tried this whole short crank thing, but i always end up with knee problems and my post nearly out of the frame(thankfully 240 now exsists)
I think the story here is poor pedaling technique if you are smacking cranks.
The pro list to longer cranks is bigger.
Lower saddle
Better knee health due to proper extension circle
More leverage, bigger gearing.
More open leg platform for stability
More outside foot weight
  • 2 0
 Bring back the IRD stroker cranks! 190mm or 220mm your choice.

At what point in the conversation does the effect of having 170mm of suspension travel become part of the pedal strike conversation?
  • 2 0
 Suspension travel is always - or should always be - part of that conversation. That's why bikes with less travel usually have a lower static BB, and vice-versa. There have been some bikes with loads of travel and a static BB that looked about average, compared to bikes with less travel, and - predictably - were ground strike nightmares to ride.
  • 1 0
 Shorter cranks are great when you need less leverage so something firm to push against. In mountain unicycling (where your cranks typically spin at the same rate as the wheel unless you run a geared hub), 150mm is actually quite long. On my mountainbike, chainring size was limited to 36t so the biggest oval ring I could fit was 34t. Smallest sprocket in the rear is 11t so I just wanted the shortest cranks I could get (and afford at the time). Been running Zee 165mm cranks and quite happy with them, though I'm open to try something shorter at some point. Fair enough, it is also a coordination thing. I'm not great at spinning super high cadences when standing so I need something heavy to push against. But I've seen BMX racers who do spin those high cadences (standing up, obviously) so obviously it is doable and then you can get away with a lighter gearing. But yeah, I think this is an important aspect. If you can't get a heavier gearing on your bike, shorter cranks will give you more resistance so that it won't feel as if you're spinning in thin air.
  • 2 0
 Im 6’2” and my element came with a 170mm crank. Dodnt notice a difference at all from my last bikes 175mm.

Issue im having is pedal strikes so im thinking of going to a 165mm.

Looks like no issues power wise
  • 1 0
 I might still just be an outlier, but short cranks don't work for me. I end up with knee pain with short cranks. I'm currently riding my gravel bike (actually on a taco break) with 170mm and I am suffering with sore knees. I went to a professional, well regarded* bike fitter (he has worked with state and national champions) and just moving my saddle down a few inches screwed me up. On the other hand, I have never had discomfort on my road race bike with a way more aggressive position and 172.5mm cranks, and my Enduro with 175's are wonderful. I just ordered a new roadie, and specifically ordered 172.5mm or 175mm cranks. My first gravel bike was 165mm, and I couldn't even ride that bike, I didn't even know why until I looked into my other bike setups.

So, I guess I'm an oddball once again.

*Same bike fitter did wonders for my GF on her road bike, and she's looking forward to returning to fit her XC bike too. Not sure about her trail bike. I do want to get her the shortest cranks I can find though.
  • 1 0
 I’m short (5’7) with a 29” inseam (or less) and started using 165mm cranks a few years ago on all my bikes. Recently, I decided to try 155’s on a low BB bike and man, does it feel weird. I was not expecting it to feel so different, but I’m not sure I’ll get used to it. I didn’t change my chainring (and the bike is SS) so I’m not sure if that matters. The lack of pedal strikes is nice, but the weirdness might be too much for me.
  • 1 0
 My experience riding flat pedals on a new 29er trail hardtail with 175's. The thighs burnt more with the 175's as expected but one unexpected negative was when I was spinning higher cadence on super bumpy terrain, my foot slipped off the pedal! I put this down to having to shift weight more from side to side and thus slightly off the pedal at the high point of the pedal stroke. I swapped to 170's, feel much more comfortable and have not had this happen again.
  • 1 0
 I’m 6’2” and have been running Canfield 155 cranks for a while now, on two bike and just ordered another set for a third. Knee and hip issue went away which was the main driver for trying, plus the add clearance is a game changer. I rode the bike with 175 cranks today and my knee hurts again, and I was pedal striking all over the place… No drawbacks from down sizing what I can tell either. As for the chain ring, one bike has a 32 oval and feels really good, and the other has a 28 ovals and often feels way too fast, and I’ll typically be in 3rd for more climbs where I’d be on the granny on the other bike… I’d stick with the ring size you are used to and only change it if you notice a difference (which I doubt).
  • 1 0
 But in the senario where your on a climb in the lowest gear and your have to push harder then you want to keep your cadence above 80 longer arms have to be better , right? I mean if your spinning slow and you have more levage you have more power. The only way the shorter arms make the same power is they feel good spinning a bit faster. But on a climb where your spinning to slow and just have to push hard to get up it your going to be weaker, right?
  • 1 0
 190cm and I've been on 170mm cranks for about 5 years, up untill recently decided to test 155mm cranks and the benefits were instant. Have to admit I was struggling with the low bb of my frame and was hitting pedals and cranks on almost every ride. Now 3 rides with the 155 and I love it! And yes if you are going for the change, consider a smaller chain ring.
  • 1 0
 At the other end of the spectrum, I experimented with 180 mm cranks for several years on my road bike a few decades ago. These resulted in lower cadence and more mashing. I immediately noticed a positive difference, on all terrain, when going back to 175 mm cranks. Now I just ride whatever is stock on the bike (always MTB now days), and it's great.
I'm 192 cm with almost a meter of spider leg.
  • 1 0
 Great article. I’m 6’5 and love the 155mm Hope cranks. Went from a 210mm to a 240mm dropper to keep the saddle low for descending. Running a 50mm rise bar instead of the 40mm I was used to keep the saddle to bar drop about the same. My old hips don’t complain are happy, fewer pedal strikes and less fatigue on descents are the benefits as Seb stated. Never going back to longer cranks on my Mountain bikes.
  • 1 0
 Of course you won’t notice a difference in power, because power is torque times rpm, lower torque compensated by higher rpm and vice versa. The real comparison should be done with constant rpm. You will note a difference I. Steep technical climbs where it’s all about torque
  • 1 0
 Sorry if this has been asked already, but what about a single speed? I currently ride 175's as "longer is better" is the common thought among the single speed type. I'd guess that dropping the gear ratio the bike will go slower, especially as I'm not much of a spinner. Thanks!
  • 1 0
 I've been riding SS on 180s for the past 15 years, swearing long cranks are the key (I'm 6'). Then I decided to go crazy and design a frame around 165s, assuming I'd hate it. Turns out I love the 165s. I didn't change my gearing either. They seem to roll over quicker and easier, especially through the low power dead spot. I ride mostly technical New England trails with lots of steep punchy climbs. I haven't found a terrain type where I miss the 180s.

It doesn't make sense to me, but that's my experience. A friend on SS also went from 175 to 170, and has had the same positive experience.
  • 1 0
 @gschwell: Cool. I’m intrigued.
I’ve built another bike with 170’s… and it’s sooo much slower. It’s also an older (retro cool), full ridged toy. So I totally accept that there are many factors between the two bikes beyond 5mm of crank length.
But when you’re getting older, have limited ride time and need to stay within a budget then these experiments get harder to do. And the less I spend on cranks the more purple parts I can buy!!!
But you have me inspired to experiment a little more.
  • 1 0
 I happened to get 175s on my bike from the factory, so that's what I've been riding... but man with how low BBs are these days, the even 5 mm of extra clearance would be great. 10 would be even better- but that'd probably mean a new dropper for me, so it's just not worth it. Very interesting read and definitely will be on my mind if I ever need to replace my cranks- I won't be afraid to go shorter, for sure.
  • 1 0
 So basically, trade ground clearance for ride-height (stablity). If I'm raising the saddle 10mm, then the bars should go with it.
and I DON'T want to reduce dropper travel!

This is another craze that will land somewhere in the middle, I used to spec 175s on my L/XL 6'2, now I do 170.
  • 1 0
 5-11" I went to 155 canfields( least expensive, available and trustworthy option i found) on my stumpy Evo because of pedal strikes on that chassis that i dont have a problem with on any other bike i own. i PR'd all my first climbing the first day out on them which i found funny as i never changed the chain ring. It's been a great experiment with no real issues or downsides that i have personally felt other than more confidence on chunky climbs, and getting deeper into corners . significantly less pedal strike issues. I will say it takes a hot minute to get used to especially cadence shifts in your bigger back cogs, shift timing , and a slight stance adjustment as mentioned above not being so far apart for balance and stability. All that said it was worth the ,money and effort, on that ride to reduce the striking and dial it in.
  • 1 0
 For what it’s worth a company called Aerozine makes an adjustable length crankset with an oval (flip chip) insert type pedal boss. They allow you to change from 165 to175 in 2.5 mm increments. Not sure how well they hold up but I’ve always kinda wished that other companies would offer this option.
  • 3 0
 So why doesn't Sram make dub cranks shorter than 165mm? I'm cheap and like my simple reliable dub BB, but I'm stuck at 165.
  • 1 1
 because SRAM makes millions of parts. Not 10's of thousands of parts. They spend millions on tooling up mass production machines. It's not cost effective and 165 - 175 is good for "most" riders in the market.
  • 5 3
 So the only real benefit is ground clearance, but you need a new crank, a new chaining and your dropper post is effectively shorter, wow, take my money Smile
  • 1 0
 I'll take your money and give you some more kool-aid. Way to take everything the article said exactly at face value and not think critically about anything that was said.

You don't need a new chainring (should _not_ reduce it, perhaps), your dropper length doesn't change, effectively or actually.
  • 1 0
 @justinfoil: Your dropped saddle height increases if you keep your pedaling height equal (wrt bottom pedal). Your feet remain at the same height with pedals level. I would call that a effective reduction of dropper length.
  • 1 0
 @ak-77: and you are higher by the crank length reduction with one pedal dropped, so same effective seat height in all drops positions.

You don't need to raise the seat the full length change either, because leg flex at the top is reduced by as much as the bottom. If you raise the seat to to fully match the shortening length, your overall leg flex is reduced by double, and that can feel just as uncomfortable as having the saddle too low.

In other words. Don't worry about "losing drop", it'll be fine, and you'll benefit more from freer and smoother pedaling.
  • 3 0
 Good Read! Are your findings based on flat pedals or clipped in? Do you think this would change anything? Cheers!
  • 1 1
 "To compensate for the reduced leverage and higher RPM with a shorter crank, you'll want to run about a two-tooth smaller chainring for every 10 mm reduction in crank length, in order to keep the overall leverage between the pedal and the ground the same."

All this talk about rigorous studies and science, and you just throw this out there with no backing evidence. Did the studies you cited make changes like this?
  • 1 0
 Surely the main influence for non XC mountainbiking would be how it affects your stance. Are feet closer together more or less stable, more control descending, or have no impact?
  • 1 1
 If the RPM is higher* with a shorter crank, wouldn't you want a larger chainring to slow it back down?

*** Except it isn't. RPM doesn't go up just because the crank length goes down. Shorter cranks tend to make it easier to reach and maintain a higher cadence/RPM., thus making a smaller ring easier to manage, but not necessary.

If you do want to make it feel the same, relative roll-out is the key thing to look at: how far the wheel goes around compared to how far the pedal goes around. Going from 170mm cranks to 160mm cranks lose about 60mm of circumference, so the pedals travel just over 2 inches less in one rev. Taking 2 teeth out of the chainring by going from 32t to 30t takes barely an inch (5%) out of the roll-out on a 51t cog, and almost 6 inches (~15%) less on a 10t cog.

In other words, don't worry about your chainring size. It doesn't very much alter the ratios in the big cogs, but makes pretty decent changes to the ratios in the smaller cogs, so you'll be relatively spinning way more in the high gears.
  • 1 1
 'A 10 mm shorter crank requires a 10 mm higher saddle, effectively making a given dropper post have less travel"

It does not effectively reduce dropper travel. Sure, the bottom position will be higher, but it's still going down the same amount. Your pelvis will also be raised with the pedals at 9 & 3, about 2.5mm per 10mm less crank length, thanks to the lower stance. So a 20mm crank shortening, like in this example, lifts you up ~5mm when standing pedals level, and a whopping 20mm higher with either pedal down. Any claim to "dropper reduction" needs to take this in to account.

And don't forget that the top of the pedal stroke is also lowered as much as the bottom of the stroke is raised. So the total leg flexion is reduced by twice the crank length reduction. I have found that raising my seat by exactly the crank shortening length makes the saddle feel very tall, since my legs have drastically reduced flexion at the top.

For a 10mm crank length reduction, just over half that (6mm) of a saddle height increase feels the most comfortable for me, since it splits the difference between changes to the top and bottom of the pedal stroke. And that brings the seat a whopping 3.5 mm closer when it's fully dropped and I'm standing up pedals level, and actually ~4mm _further away_ when I'm standing with one pedal down... An _increase_ in "effective dropper length" by this article's logic.
  • 1 1
 This is the mountain bike journalism we deserve. I will probably say the only downside to this, especially with going to a significantly smaller front chain ring will be all the top end speed you will lose if you ride high speed terrain. If this is only in bike parks for you, then ignore it. A place like pisgah though with hard single track climbs to to super fast descents, this could be interesting for some.
  • 1 0
 You don't lose top end speed though. The leverage you have ends up being the same. And you can spend at a higher cadence on the shorter cranks, because the foot doesn't have to move as far with each rotation. So by adjusting the chainring size top end speed and low end speed stay the same
  • 1 0
 @sdurant12: In theory yes. But if you’re spinning out at the same cadence for both crank lengths (say 120rpm), it just comes down to gearing for top speed. The question is (and to your point), is it easier to hold a high cadence with shorter cranks than longer ones? And I think the answer to that is yes. FWIW on 155 cranks I’m still pedaling my natural cadence (80ish) compared to my trainer w/ 170 cranks. So other than the gearing reduction, it actually feels pretty normal to me. That’s with a 4tooth chainring reduction (to 26t on a 29er), though.
  • 3 0
 But why aren't they still used by professionals in XCO or road cycling where efficiency is most important?
  • 1 0
 Tradition.
Remember how long it took for 29ers to be adopted in racing?
Or wide tires on road bikes?
Or the benefits of aerodynamics?
  • 1 0
 IDK, I'm really short (5'4") and went up from 165 to 170 / 30t to 32t and it just feels better to me. Some pedal strikes at first but I got used to it and instinctively position accordingly now. To each their own, I guess.
  • 1 0
 I went from 175mm to 165mm cranks and the only differences I noticed where less pedal strikes and having to raise the seat a bit. I didn't notice a bit of difference as far as pedaling.
  • 1 1
 This is a great article topic! Thank you pinkbike! One more factor i'm considering is the ability to wedge your feet when riding platform pedals. The front foot needs to point up while the rear points down. This provides enough traction to lift up on the bike without losing the pedals. Being slightly closer together could affect how easily or effectively that is done.
  • 1 0
 If your dropper post would be higher then with shorter cranks, would this also mean it would be marigianlly easier to get over the back of the bike?
  • 4 0
 If you are talking about a standing position, probably not, as most movements would be from level (ish) pedals.
  • 3 0
 Wouldn't it be a bit harder (since the saddle is a bit higher, while the center of the crank = feet height remains the same)?
  • 2 0
 Probably not as you would likely be doing so with your cranks level (horizontal), which might bring your front foot back but would also take your back foot forward so net position fore/aft would remain the same
  • 2 0
 I don't think so. Your stance height is based on leveled pedals, and that height doesn't change with crank length.
  • 3 0
 If you mean seated position, your saddle will be a couple of mm further back. If you extend your seatpost by 10mm the saddle will move backwards by 2.5-3.5mm on most bikes. Idk about standing up position, I suspect having your back foot further forward would be more important than having your front foot further back, so it might actually feel slightly harder to extend yourself backwards. I'm just guessing though.
  • 2 0
 Why do you want to get over the back of your bike?
  • 4 0
 @paja-tousek: Actually, it does. Feet closer together will raise up your "stance height", about 2.5mm per 10mm crank length reduction.

Geometry! Or trig? Maths, in any case!
  • 1 1
 @BrianColes: steep descents, drops, etc.
  • 3 1
 165mm was the sweet spot that fixed ride height for me, without needing to drop saddle height...
  • 2 0
 Been there twice (165 and 170) and gave it a full month both times.

Hated it both times.
  • 3 0
 love the high IQ, thoughtful content pinkbike!
  • 3 0
 Hah! a 29-teeth narrow-wide chain ring does not compute!
  • 1 1
 Y'all please stop talking about crank lengths, holding your cranks (level), smashing cranks, etc. I'm trying to work and snickering uncontrollably is a bad look at the office.
  • 1 0
 Anyone running 165's and an oval chainring? Love my oval, not sure I want to give that up for the shorter crank length. Maybe it doesn't matter at all?
  • 1 0
 I'll bet you'll find shorter cranks alone give a good chunk of the oval feel, specifically that "getting over the top of the stroke faster/easier" feel. I found ovals gave that feel but also made me try to pedal a faster cadence than the average gearing of the oval should have. This burned out my legs, despite the added traction from smoothness of pedal stroke thanks to the over-the-top feel.

In other words, short cranks might obviate your need/want for ovals, but they also will work just fine with ovals.
  • 2 0
 @justinfoil: Thank you for the insight. I'd like to think I have a medium cadance, not a masher but not a high spinner. Probably 80ish RPM on average.

I've been thinking about new cranks for my bike and I might just try it!
  • 2 0
 I’m running 155s with oval and it’s great.
  • 2 0
 Sounds like bike geometry isn't so perfectly sorted yet as we're all assuming.
  • 2 0
 In a short, they are still selling us bikes for 10k with wrong cranks lenght
  • 3 0
 Y'all are still using cranks? I only use pegs
  • 7 0
 technically, ur girlfriend uses the pegs.
  • 3 0
 @savagelake: wife actually
  • 3 0
 Another suron rider, thinking they are on an MTB
  • 3 0
 Cook Bros RSR 181mm...anything else feels like shackles!
  • 2 0
 i just built a nomad with 165s, and i'm 6'1". only diff i noticed was less pedal strikes.
  • 1 0
 Bike industry - We got containers of short cranks to move since we messed up in the pamdemic, you all got new bikes so here… Time to upgrade
  • 1 0
 I ride 170 because guess what? It came with my bike…

At 5’5”, sure I’d like to try shorter cranks but… it should be specced on the bike…
  • 2 1
 While I appreciate the article, endless comments perseverating about crank lengths make me want to throw my bike into the ocean and take up pickleball.
  • 1 0
 IF short cranks are so great when tested in a lab, why do my 165s climb like garbage? Also technical power moves are weak with 165s.
  • 1 0
 You what works for all riders? Cranks with steel pedal inserts. How often have you replaced a Saint or Zee crank? That's what I thought.
  • 1 0
 Wonderful comprehensive video and very interesting take on crank length! Can't wait to break my current 175mm carbon cranks Smile
  • 2 0
 Appreciate the in depth look at this!
  • 2 0
 Besides Hope and 5dev who makes cranks shorter than 165?
  • 13 0
 Canfield has been at it forever
  • 5 1
 @crs-one: Don't you love it when a new brand comes out with a 160 crank and everyone is like "wow, first of its kind!" Canfield, meanwhile...
  • 1 0
 Bought my 155mm NX cranks in 2019...not sure if they still make them though. (5'10"/177cm and long legs for my height.)
  • 3 0
 @WaterBear: also loved the Jedi review here, where the truly smart commenters accused Canfield of jumping on the high pivot bandwagon, copying forbidden and deviate.
  • 2 0
 Appleman - but they have chosen a 104 BCD mountain bike spider rather than a direct mount standard which limits one to 30T chain rings so not really ideal for smaller/ weaker riders who need to gear down.

Northshore Billet are considering a run of shorter cranks if the demand is there. They have gone with Raceface DM standard.
  • 1 0
 @andrewbikeguide: They have 155's in stock right now
  • 1 2
 Check AliExpress.
I got mine for 25$. The brand's name: Cruz bike.
Working just fine.
  • 1 0
 @crs-one: And they're great at it!

Although, FYI, they don't cooperate with the Wolf Tooth BashSpider. I had to caress my 160mm Canfields with a grinder a bit to get the spider to sit properly.
  • 2 0
 @knightmarerider: those savings only count if you live in a country with socialized medicine.
  • 1 0
 @TheRamma: it's an option to try ergonomics without shelling out crazy money for pair of spindles.
  • 1 0
 @andrewbikeguide: one up solves that problem, FYI.
  • 3 0
 Hopes cost a fortune. Which I grudgingly paid for 155 cranks on one bike, after 10 years on 165. Another bike was cracking rocks at 170, but this time found MIRANDA 155s. Very cheap but fitted fine, arrived fast from Portugal(?) looked ok, haven’t broken and for me no difference in flex or feel compared with the Hopes. They have a huge range of lengths and fitments online and the descriptions can be confusing at first so select with care, then celebrate sensible pricing.
  • 1 0
 I may have to give this a try, I'm on a verrry modified XXL top fuel and a little more ground clearance would be nice.
  • 2 2
 So many people just had their ego boosted after arguing to their friends about crank length, and now there is decent science to back it
  • 6 0
 The "decent science" is from 2001. The only thing new is this PB article about the old research.
  • 1 0
 And the science, like most sports science papers, is not very decent. They all suffer from too small group sizes and too few repetitions. Not the researchers fault, this is not medicine, nobody is willing to pay a few million euros for a study about crank lengths.
  • 1 0
 Ive gone from 175, to 170, to 165 and now to 160 and each decrease definitely makes a noticeable improvement
  • 1 0
 When your feet rest on the BB,you've reached nirvana!
  • 1 0
 @lenniDK:
You mean, like moto’s?
  • 1 1
 I've always felt that crank length should be a percentage of inseam/leg length. End of story. If you need more ground clearance, choose bike with a higher BB
  • 1 0
 Even going from 170mm to 165mm cranks made a huge difference for me in the pedal strike department.
  • 3 5
 Seb always does fantastic work, but I hate this trend of shorter and shorter cranks. I've got a bike with 170s, and another with 175s, and the 175s always feel better to my long legs. A bike that comes with or necessitates 165s will be a deal breaker. When you've got guys like Jeff Kendal Weed saying bottom brackets are too low, you know something is wrong.
  • 1 0
 Went through this last year, spent the money on 165's and 160's including a new chainring. I ended up back at 170mm. The biggest issue for me was the 10-20mm closer foot stance when the cranks were horizontal. I'm tall guy and I like my legs more spread apart for stability when jumping and pumping. The 160's felt like I was mono boarding on my bike (not in a good way). 175's feel the best but it's almost impossible to ride with all the rock strikes.
  • 2 1
 @dirtdiggler: That's a valid point that the short crack advocates don't acknowledge, and is probably more noticable for taller riders. Long cranks also allow you to have more leverage in maneuvering a bike with your feet, especially if you are clipped in. Pros instinctively use footwork and foot pressure to manipulate the bike in turns to get more traction, or in the air to scrub, without even thinking about it.
  • 1 4
 So because you have long legs, all bikes should have long cranks? Stellar reasoning.
  • 1 0
 This has given me the motivation to put shorter cranks on my Transition Spur. Way too many strikes.
  • 3 1
 choose a crank length and be a d!ck about it! 180mm's for life!!!!!!
  • 2 0
 You running 2009 Hussefelts?
  • 2 0
 All I know is my knees hurt less on 170 than on 165.
  • 1 0
 And what about the Q factor!!!!!?????
Over 800mm wide handlebars but our feet must be tied together as half a century ago?
  • 6 6
 So now instead of having pedal strikes during climbing, you hit your nuts on the saddle during decending. Revolutionary!
  • 3 0
 Huh? Shorter cranks would let you run a slightly longer dropper length.
  • 1 0
 Pros and Cons when descending would be good. Sorry if I missed something
  • 2 0
 Bikes
  • 1 0
 Shimano, please make 155 & 160mm SLX and XT cranks.
  • 1 0
 Cut some old ones down and drill then tap em out. 135mm
  • 1 0
 well I guess noone makes odd-numbered narrow-wide chainrings Smile
  • 1 0
 As always, more Seb articles!
  • 1 0
 I have 175s on my mtb now I feel guilty?
  • 1 0
 Dear PB editors- you've struck a nerve! Good luck! : D
  • 1 1
 Anyone know where I can get a 29t narrow/wide?
  • 2 0
 Take some air out of your shock and ride chunky trails; you'll soon have 29T ... then 28T, then 27T ...
  • 1 0
 Greate article
  • 2 4
 I had 155s on my tricycle when I was 3 years old, when I grew up I switched to 175s on my mountain bike!
  • 1 4
 invalid test. You can't change two variables and come to any sort of conclusion. Basic 1st year high school science.
  • 2 5
 Very well written. Ai? Lol
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