Words: Matt Wragg
Photos: Satchel Cronk & Tom RichardsAs reaches have grown, what we think of as "short" and "long" chainstays needs to start shifting as well.It is no secret how chainstays affect the handling of a bike. Even a dry, technical document like the
UCI technical guidelines states very clearly what a shorter or longer chainstays does. Yet to read the forum discussions and marketing material around them, you could be forgiven for thinking that there is some dark magic going on back there.
| If the front or rear center is too short, this will reduce the bicycle’s stability whereas if the front or rear center is too long the bicycle will be less maneuverable.—UCI Technical Regulations |
As a whole, geometry’s evolution from old school to modern has not been a smooth-flowing process—it comes in drips and drabs. Take reach for an example. Mondraker drew a blueprint for longer reaches more than a decade ago, but it is only recently that we have been able to have intelligent discussions about it. I think Matt Beers’ recent editorial represents a growing understanding that reach isn’t some magic number for brands to compete over, but an actual
functional part of bike fit and performance.
To understand the question around chainstays, you first need to fully understand what has happened to reach, and to a lesser extent, headangles. Yes, wheelbases got longer, but by how much? It is hard to find old reach values, if for no better reason than it was not a common metric on geomerty charts a decade ago. But there’s one bike I know, so I’ll use it as a benchmark: the original Ibis Ripley. Yes, it was launched in 2013, but Ibis were conservative even back then. The large had a 406mm reach and Mike Levy liked to tell everyone that
all bikes should be like the Ripley. Today, the current large Ripley has a 475mm reach—a growth of more than 60mm—which is still on the conservative end of the scale compared to some brands.
Indirectly, this goes a long way in explaining the industry’s fixation on short chainstays. If your reach was 406mm, the diameter of a 29-inch wheel prohibits getting your chainstays short enough to even match the reach. With a bike this short, every millimeter shorter probably felt better, and this is how dogma emerges. Unsurprisingly if you add 6 centimeters to the front center of a bike, the overall balance dramatically changes. Balance is the keyword in that sentence—I believe the next big step for progress is starting to have sensible discussions around chainstay length and to stop using descriptors like “nimble”, “playful” or “snappy” around them.
I’m 1.75m/5’9” – an average-sized human, more or less. Last summer I was on a 29er with 465mm reach, 64-degree head angle, and 435mm chainstays. Coming off a few years of almost exclusively running longer-chainstayed bikes, the first thing I noticed was the weight distribution. Initially, it manifested as less weight on the rear axle, so less traction.
The first consequence of me trying to mitigate this was to hang off the back of the bike to keep the rear wheel traction at the level I was used to from my other bikes. Soon I began to realize that this tactic was compromising my riding because I couldn’t be off the back and put enough weight on the front end at the same time, so the bike started to understeer. Realizing this, I turned a few dials and had a little chat with myself about riding properly.
Pushing my weight forward brought the steering back under control, but there was a compromise again. With my weigh forward, there now was not enough weight on the rear wheel. I could feel it in every corner, I had to delay my exit just a little longer to let the back of the bike compose itself. If I tried to be aggressive and exit early, the rear would oversteer and break away. With the rear slightly unweighted like this, I was not getting enough feedback and it felt like it was going away from me without warning. Waiting like that in every corner felt like I was losing so much speed.
Maybe this oversteer is what people mean by “playful” chainstays? Certainly, it makes intellectual sense – less weight on the rear axle will make it easier to pull after you, although I am not convinced there is a benefit there.
In the past I had another bike that was doing something similar. It was a 29er with a 450mm reach, 66 degree headangle and 435mm chainstays. I noticed the front-to-rear imbalance, although since it was a shorter travel bike I noticed it more on the climbs when the rear would slip away from me under power. On that slightly smaller bike, I could solve the issue by adding 10psi to the fork and going from a 50mm to a 40mm stem. This shifted my weight backward and I felt much more centered on the bike and the bike stopped slipping out.
On the bike last summer, though, I was out of options. Maybe I could have found a 180mm fork, or tried a 32mm stem instead of a 40mm, but both of those came with downsides that did not appeal to me. Looking back, I wonder if dropping from a 30mm to a 20mm rise bar might have helped. Maybe there was more I could have done with the suspension? At the end of the day, my feeling is that if you have to go to those lengths to feel balanced, then there is a fundamental flaw with the bike’s geometry - a balanced bike should be able to accommodate a wide range of settings.
After years of experimenting, I now have a preferred minimum chainstay length – 440mm for a 460mm-ish reach bike, although I also have a 450mm chainstayed bike, and that feels even better. The longer stays seem to flex a little more, so the feel at the rear of the bike is superb. I cannot find a downside to running chainstays at that length, in fact, I feel longer chainstays help me be more playful with my riding as I feel centered and balanced on the bike. Talking to a few people about my ideas, I have yet to find someone who has offered me a coherent performance argument for shorter stays - I'd love to hear one.
Maybe what we need is a recalibration of perceptions? A few years ago 420mm was a short chainstay. Today it is 430mm, why couldn’t it be 440mm tomorrow? More interestingly, people like Seb Stott are starting to ask questions about
what happens if we go even longer.
Implicit in all this is the idea of proportional chainstays. If there is a relationship between reach, head angle, and chainstay length, it follows that if you change one you will need to change the others. In the absence of a golden rule for proportion, how are bike companies going to make bikes that give a similar riding sensation at their smallest and largest sizes? Some brands do proportional sizing that addresses this by changing rear-centers along with reach, but most still don’t, and none offer a choice of chainstay lengths. Will the industry as a whole see the importance of balancing bikes, or will the sole chainstay model most brands have continue to prevail?
Maybe the OP needs to buy an Atherton so they can spec exactly what geo they want???
"More analysis might be required here"
Now draw another segment, from the center of the bb shell perpendicularly to the ground.
It will bisect the wheelbase in two, the front center and the rear center.
I have a Commencal Meta with 63.5 HA, 495 Reach and 433 Chainstay, so i have pretty much the shortest chainstays possible in relation to the rest of the bike. I thought a lot about rear to front center balance, and of course, the short chainstays mean that you have about 2/3 of your weight on the back wheel, while the front is relatively light.
This is very noticeable while riding, you really have to weigt the front and adapt a very aggressive position, especially on mellow terrain. Otherwise the front easily washes out and you dont get good front wheel grip.
I countered this to a degree by increasing sag in the fork and decreasing sag in the rear, so that the weight distribution at sag is a bit more front wheel heavy.
I would think that increasing pressure at the fork for less sag like matt suggests would have the opposite effect.
I guess his thinking was that more fork sag means more reach, but we are talking about wheelbase and front- to rear center ratio here. With a slack head angle the shortening of wheelbase and front center as you go through travel is a lot more substantial than the increase in reach.
Your handlebars might still be closer to you, especially if you have a lot of spacers under the stem. As you slacken the steering axis, the stem is pointing more backwards and with some spacers, it might actually come closer to you. but this does not affect the reach measurement, as it is taken on the frame and determined by the head tube, not the actual place your handlebars are at.
Matt's statements also do make more sense in relation to HIS riding style and preferred wheel size. A 420mm chainstay length is still both playful and stable in a 25.7" wheeler bike.
So many words in here where it's all pretty easy to summarize:
1. Around 2017 everyone started noticing that more front center (more reach and slacker head angles) and getting the hands further behind the front axle made bike more stable and less prone to OTB events.
2. The increased above started making seated cockpit lengths too long (even with shorter stems). Seat angles got steeper to compensate. Turns out that on steep uphills this also compensates for rear suspension sag which in many scenarios improves climbing overall.
3. Once the dust settled on the front center increases it was noticed that weigh balance was compromised. Chainstay lengths have started to increase in proportion.
That's it.
The more interesting discussion is what are the tradeoffs of these "improvements"? Is more always better?
The obvious answer: It depends.
Where articles like this seems a little wierd is they make the assumption that these changes are universally better no matter the use case or riding style.
The rearward movement of the handle bars with the angle adjusting headset in the slack position causes the reach to shorten, but the rotation of the bike downward, due to the reduced stack height, counters this and you end up with values very close to where you started: a couple millimeters, it varies depending on the rest of your frame geometry. In my opinion it is basically negligible.
On smooth terrain the only advantages to changing sag in such a way will be the geometry shift, because the dynamic grip is then irrelevant.
This is the reason my elementary school science teacher could lift his car in the parking lot by building a long wooden lever, placing the axis near the car, and using his body weight at the end of the lever arm.
Don't believe me? Try it for yourself. Go sit next to a door and push that door open either from the inside (hand near the door hinges) or on the outside (hand near the handle). Your hand position near the handle will require MUCH less force to move the door.
Archimedes said it best, "Give me a lever long enough and a fulcrum on which to place it, and I shall move the world." He was being literal. Longer levers = more force applied on the opposite side of the fulcrum.
Imagine you are going to be hit by someone wielding a baseball bat. Would you like to be hit by a normal sized baseball bat, or a 6 inch baseball bat? 6 inches is the correct answer (assuming you value your health). The reason is because the force realized at the end of the bat is GREATER if the bat itself (the lever) is longer.
This is also why golf drivers are longer than irons are longer than putters. More force in the longer lever, more control in the shorter lever.
As for the wheel balance thing here, I think there should be a poll. I vote for: shorter chainstay wrt the wheelbase, more weight over the rear wheel. On my previous hardtail, I had a 420mm chainstay and a relatively short wheelbase. Not sure what it was, but I think horizontal top tube was 375mm or so and head tube angle must have been 69deg. This was a DMR Switchback, which has their Trailstar geometry. Especially once I moved my feet from ball of the foot over the pedal axle to midfoot over the axle (effectively stretching the rear center even more) the rear end was completely out of control. It was near impossible to keep the rear from drifting. Which was fun in a way, but hard to maintain speed. And I had some bad crashes because of this. So on my next frame I consciously went with a shorter chainstay and longer front center (415mm chainstay, 460mm reach, 1213mm wheelbase, 63deg HA). Both bikes have five inch travel forks and 26" wheels, so no changes there. Now it is nicely balanced. I can shift my weight rearwards to the point that I get understeer and I can shift my weight forwards to get oversteer.
S2: 417mm (likely not possible)
S3: 433mm
S4: 448mm
S5: 463mm
My views on this will always be skewed because I'm a long time mountain biker who is big and tall and I only feel like they actually started designing bikes for taller riders in the last dozen years with steeper STA, longer TT's and longer rear swingarms...
I'll try another one. Carry a beam with two people and put one person (considerably heavier than the beam) on top. If the person is in the middle, both carriers experience the same load. If the person walks all the way to the rearwards person, that person will have to lift more weight. If the person walks beyond the rearwards carrier, the front carrier will eventually have to pull down to keep the beam horizontal (and the rearwards carrier will have to carry everything plus what the front person pulls down).
That kinda brings us to the situation of looping out. Of a (motor)bike on an uphill slope, in the horizontal projection the center of mass shifts closer to the rear tire contact patch. This is because in this center of mass is above the wheels hence when the bike tilts backwards, the center of mass moves backwards too. Not just that. The tire contact patches more ahead of the wheel axles in this horizontal projection. So yeah indeed, you'll get more traction over the rear tire contact patch when climbing and at some point you may even go beyond this patch. This causes you to loop out as unlike in the example of the beam, the front carrier (your front tire) can't pull down. In the dynamic situation (you try to accelerate up that hill) you could even loop out even if your center of mass isn't behind the rear tire contact patch (in this horizontal projection again) but I won't dare to discuss dynamics at this point as I can't make drawings in this comment section. But yeah, if this is a concern (looping out, not the lack of traction), people may opt for a longer rear center.
TL;DR: Don't shoot the messenger.
But I think this is the heart of the matter for me. It's climbing that longer rear ends have been a nite and day difference to me. undulating and DH I can still ride fine with a "longer" rear end. So win/win...
I think most people think of shorter chainstays as being more playful because shorter chainstays typically make manuals and bunnyhops easier. The front end is typically easier to lift, so for most that equates to being able to play around a bit more on the trail.
Having had a quick play on bikes with longer stays, they definitely feel like more work to manual or pop over little kickers and jumps. I know someone who switched to a high pivot bike with a decent amount of rear centre growth through the travel, and they ended up getting rid of it because further into the travel as the rear centre extended it made popping the front up on awkward/techy lines harder than they liked.
We're all the rider we feel we are inside.
But I do think longer stays would suite most riders that prefer to plow than play.
Curious, what size Process are you on, and how tall are you?
I had that exact bike (the 29'er variant), but eventually sold it because of what felt to me like "too short for me" chainstays.
Funny enough, the latest revision of the Process 153 has 435mm chainstays (and a slacker 64.5 degree HTA, vs the original G2's 66 degree HTA). So I wonder if they were trying to keep some balance/ratio there with the update vs the original design.
But the thing is, if you want long chainstays you are spoiled for f*cking choice, if you want short chainstays you are increasingly shit out of luck. 435 is now considered short FFS.
There is a reason that every discipline of riding that needs manouverability and "playfullness" goes for the shortest chainstays they can manage. BMX, DJ, Trials etc.
Sure, if you just want to plonk yourself down on the seat of the bike and aim it straight up or down a hill then long chainstays are probably ideal, but there are a lot of us that want to have some actual FUN!
totally agree. Not a pro but I can hop and manual my Remedy no problem and its great fun. It takes a fair bit more effort but I can get the front wheel up on my Session (27.5" wheel) at will and with confidence. I recently got a custom-geo HT. 29r, shortest CS I can go with my current wheel is 445mm, 315mm BB/60mm drop and I can barely lift the front wheel over a curb and even that takes a herculean effort. Its stable and corners very well but overall I'm somewhat disappointed with the thing.
G-spot's comment about plonking down on the seat and aiming it straight down a hill is, I suspect, is largely what we get from bike reviewers.
but i agree on his statement that balance is crucial - having tried several bikes with similar reaches (490-495), and chainstays ranging from 420-445; the longer rc bikes were the best cornering / dynamic handling (best at fast directional transitions, etc).
And how is it physically possible that hopping on a shorter chain stay bike “manifested itself as less weight on the rear wheel”?
**Disclaimer— long-standing short CS advocate here, though presently less dogmatic than I used to be.
Can you explain how shorter chainstays result in LESS weight on the rear axle? This doesn't make any sense to me. The closer your center of mass is applied to an axle (the closer your bottom bracket is to the front or rear) the more weight, and therefore traction will be applied.
The reason people like longer CS bikes is because it applies more weight to the front wheel via the feet.
Consider how weight distribution affects climbing, too much weight back and the front end gets light, too much weight forward at the rear end gets light; simple physics.
A longer RC increases stability, but does not increase traction, weight transfer is what creates traction.
Still, physics don’t lie, but people gonna be what people gonna be …
Yeah kinda unfair I suspect people aren’t quite understanding what you’re saying but I think you’re closest to interpreting what Matt is sensing but not saying: he is compensating for the short CS by putting his weight forward on the bike (which is what you need to do cos there’s less weight on the front wheel), but that he’s finding this compromises his riding style relative to a more balanced bike.
It’s the physics of the compromise which is less obvious, but it seems reasonable to think that a bike which demands you to lean further forward in corners may not corner so well. To postulate, perhaps the problem relates more to consistency of grip generated because of the relatively more limited mobility of having to commit more weight forward and to an extent through your arms (think being on the drops on a road bike as an extreme example), rather than being more centred, driving weight through the BB and being able to make small adjustments more easily.
Anyway, this article all feels like a bit 2020. Chainstays are getting longer. More bikes are coming with size specific CS. This is old news
I like bikes with longer stays, because they feel more 'jibby' (since many get persnickety about the use of the terms 'lively' or 'poppy', perhaps this works better). I've always liked Evil bikes because they definitely have this ride feel. Shorter stays contribute to that feel.
I also like longer and more stable bikes. They feel more stable and composed, and tend to corner and carry speed better.
The one thing I think we need to get away from is the notion that any specific geometry is inherently better.
"Initially, it manifested as less weight on the rear axle, so less traction"
Shorter Chain stay bikes put MORE weight on the rear tire, not less, like you mentioned. This is a pretty simple math equation, lever/load situation. That's not to say what you are feeling is wrong, but your explanation of it doesn't really add up. I believe what you are feeling is that a shorter chain stay bike has more grip on the back tire and thus less on the front. In order to get the front to grip, you need to lean forward more, and thus, you are all out of balance and when the rear DOES lose traction, it is FAR less predictable of a slide than a long CS bike. It "Snap" oversteers quicker.
I too find long CS bikes a lot more fun and playful bc they let you goof around so much more within the bounds of grip. But I believe that is because the edge of traction is far more predictable than an imbalanced short CS bike. There is no "right or wrong" but a 490mm reach bike with a 425mm CS length is certainly an imbalanced bike. whether that is fun or not is subjective.
I'm sure there's a ton of stuff that we're not fully considering about biomechanics like flexiiblity and strength and leg vs torso vs arm length, without even getting in to your riding background, but for a bum average rider like me it''s more predictable, friendlier and more fun to ride than most other bikes I've owned.
This is operating on the assumption that everyone wants similar bikes, and any deviation from that is an error. There is (and should be) significant space for personal preference. If that works for you, great. But its also fine for different people to like different bikes.
I think threre is no other Bike Company out there that delivers the same Frontcenter/Rearcenter ratio between al sizes appart from Forbidden.
And ive been to the Tropy of Nations Race lately, never seen so many Forbidden Bikes. Racers seem to like the Idea of a balanced Bike aswell, atleast some of them.
I do agree with you though that Forbidden is, not the only, but certainly a rear company that is doing the balancing right, with many other companies now touting proportonal chainstays on their new models, while in reality they are just offering a couple of milimeters increase in RC for additional centimeters in reach. Hardly keeping a balance.
TLDR: People who grew up with BMX, or other small bikes might prefer shorter chainstays and the playful/poppier riding style. Whereas people who grew up on dirt bikes or other larger things, may prefer longer.
A buddy and I both like riding. He is 2-3inches taller than me, but was VERY good at BMX/Street riding as a kid (qualified for the X games at age 15). I grew up trail riding dirt bikes (Honda XR's).
Bikes that my buddy describes as being a "plow" feel "twitchy" to me. Bikes that feel normal to me, he describes as an "ocean liner".
Turns out, he rode countless hours more on bikes with near vertical HTA's, and tiny wheelbases (and has the skills to back it up), while I grew up riding dirt bikes with 62 degree HTA's, and 1400mm plus wheelbases. So that colors our perception of what the bike should behave like.
Offhand I think its still fairly split between "short" and "long", although "truly short" may be getting rarer these days. And I do think the average is starting to move up, especially on size L and XL frames.
Here are some random ones I can think of for those wanting "short" to "quite short" 29'er chainstays.
Commencals Meta TR (435mm)
Commencal Meta AM (433mm)
Canfield Tilt (425mm)
Canfield Lithium (430mm)
Specialized Status 140/160 (both with 426mm)
Kona Process 134 (426mm)
Kona Process 153 (435mm)
Kona Process X (435mm in the short position)
Totally— plenty commenting here on how longer CS generally feels more balanced, and “corners” better. I wouldn’t know. On my favorite trails here in the Northeast, and the ones I learned on, not sure I’ve ever “carved a corner”— every change of direction is mid-rock, root, step-up, log-over, off camber, rock ramp, mid-stream, or something else. Check Debacle at Blue MT. Map looks like a bowl of spaghetti but damned if you’d find a corner anywhere on that trail. I learned to ride in a style where you’re lofting the front wheel, or floating the rear, or some other body English to make virtually every turn. Part of my penchant for shorter CS.
What do you think is the ideal BB drop vs wheel size vs rear centre vs etc.?
If the point is that chainstay length should generally scale with reach to allow a weight distribution balance, then just say so up front (and for the record I agree).
Really, though, the underlying issue is that for 99% of us (me too) there's not an *objective* ideal. There's just a subjective one, where we feel the speed/flow/whatever and just have a blast.
-W
Im a firm believer in fully adjustable bikes, why cant i have a 435 or so CS for my locals and then adjust to 450 for the park etc? does this compromise sales?
Theres many that disagree which is fine, They just dont understand how suspension works lol
"Theres many that disagree which is fine, They just dont understand how suspension works lol"
If you're going to school us all about it maybe try a bit less hyperbole and stick to the facts.
BTW, there is a spell check on here.
“Coming off a few years of almost exclusively running longer-chainstayed bikes, the first thing I noticed was the weight distribution. Initially, it manifested as less weight on the rear axle“
"Coming off many years of exclusively running shorter-chainstayed bikes, the first thing I noticed with the longer chainstays was the weight distribution. Initially, it manifested as less weight on the rear axle, and consequentially less traction"
And while impressions are a personal thing, these impressions in particular, unlike Matt's, are backed by facts. It's undeniable that the shorter the chainstay, the more weight is concentrated on the rear axle.
As a taller person on a short bike, I have to get back over the rear tire or I feel like I'm going OTB. Then my weight is back and it's hard to get good front grip going into the turn. Short bikes just take a lot more weight shifting vs a longer, 29er wheel bike where you are more centered in the bike instead of sitting on top of it.
Seems to be why DH bikes have been getting longer in the last 10 years, especially for the tall DH pros.
But longer CS's also give you more front end grip if nothing else is changed. So you have more room to play with stack, without having to keep it super low to keep weight on the front. So you can move your weight up, which helps body positioning, and bunnyhopping and manualing (as you're not folded over the front quite as much).
So for me, manualing and bunnyhopping feel about the same on my long chainstay bike, as my old short chainstay bike. But thats because my long chainstay bike has 20mm more stack, so I'm "starting the manual further into the process", so to speak.
But totally agree it is a factor to consider. Just saying its not been as noticeable as I thought it might be personally.
Totally with you on that, but thanks for calling it out .
I've got only 5mm of spacers, and a 38mm riser bar (I'm borderline between L, and XL, and went L), in an attempt to maximize the reach I have.
But that means I've got 20mm more stack from the frame + 13mm more rise from the bars, at about the same reach as my old short chainstay bike. So its not felt as much different to manual/bunnyhop as I was worried it might, thats all.
Probably why I cant manual very well lol
Ironically, I’m a newer rider to the sport, so I didn’t really have a dogma to start with. I started riding late in 2018, and my first bike was a G2 Kona Process 153 29’er with 425mm chainstays. And I found I had to keep removing stem spacers and go to shorter rise bars to keep weight on the front tire, so I started exploring other bikes. At 6’1”, I’m now on a Banshee Titan, with 452mm chainstays, and I’m considering trying the longer ones.
My favorite way of comparing bikes weight distribution is finding their front center/rear center ratio. This accounts for reach, head tube angle, and travel. It’s really interesting to see how some bikes are VERY differently weighted than others. The forbidden dreadnought in XL, vs a Canfield Lithium in size XL for instance.
I also am starting to think flat pedal riders may prefer a bit more chainstay length. As you drop your heels for stuff that shifts your weight back, which means a more rearward weight distribution than someone on clipless pedals.
Cleats increase control and allow a rider to manipulate a longer chainstay.
I'd think a shorter chainstay would be more agile, no matter the pedal type. And agile is another way of saying "less stable", so no argument there. And agree on shorter CS bikes being easier to manual.
Ironically, I don't notice chainstay length at all in a straight line going "mach chicken". For that I'd think that wheelbase would be the main thing you notice.
Personally I notice it entirely in turns, where, I find weighting the front wheel much more intuitive. I'm not having to fight front end washouts really anymore.
Then again, I'm relatively tall (6'1" barefoot), with very long legs (36.5in saddle to pedal height). So even if I stand and hinge at the hips the same way as most folks, my torso being shorter, and legs being longer means my weight is usually farther back.
Stuff like this though is why I love seeing adjustable CS lengths in bikes now (RM Altitude, Kona Process X, Stumpjumper Evo, Raaw Madonna, etc). So both of us can have our cake and eat it too .
The only thing I really like about short CS's is easy manuals, and exceptionally slow techy steep riding. But, as I get better, I'm riding those steeps faster anyway so the benefit is waning.
One takeaway is that quote about Levy 10 yrs ago and the Ripley. Whatever we say/think now, probably can't treat that like Gospel unless its been extensively tested with a proper sample size of people, track types etc.
Also, why are you on such a long bike at only 5-9? Hell even transition says you'd but on a medium Spire lol...with 455-460mm reach (albeit with their 35mm stem too...further shortening things).
Are we sure you aren't just simply riding a size too big??
Chainstay length doesn't change bike's balance that much, if at all.
A big part of riding your bike is to move your CoG at the right place. So a longer reach gives you a CoG that will probably be a bit more forward, hence giving you a longer rear center, without adjusting anything. Maybe that'll put more pressure on your hands.
Everything in the article could be related to others factors, like suspension characteristics, tiredness, or the color of the bike. you are trying different bikes, you'll have different feeling.
Yeah.
Horses for courses, but we all know there is no magic formula because every bike is different, every trail is different, every use is different , and every rider is different.
The fundamental flaw in this argument is:
bike manufacturers choose the chainstay length due to tire clearance. A longer chainstay is required for larger wheels (29 vs 27.5/2), a longer chainstay is required for bigger tires (2.5 vs 2.0), and a longer chainstay is required for more travel and for sone suspension designs.
So yeah, just another opinion from a non scientific rider who has an ideal that is based entirely in their experience.
Thanks for sharing!
Then do it. We all dare you.
However, short chainstay bikes with a long front end can be a blast. Not as fast, but easier to manual, cutty, and throw shapes in the air.
Like setting up a car for drifting, a short rear end is a blast…..but not as fast.
What? Shorter chainstays will put more weight on the rear wheel.
@adamdigby I agree that on XL and over the CS needs to grow a little. But for anything under XL, no.
most large size bikes are pretty good if their reach isnt in XL zone like some are getting.
I mostly notice it on fairly flat sections. When it's steeper, I'm somewhat automatically weighting the front, so it's not an issue, but a couple of times lately I've scared myself a little on the more open, flatter, faster runouts at the bottom of the trail. Part of that is me - as I relaxed more than I should have, part is the conditions as a heavier than usual monsoon left a lot of sand and small rocks on our trails, but part I think is the need to keep weight on the front more aggressively due to chainstay length.
That being said, I wouldn't want them that much longer. Maybe 445. I'm not an amazing bunnyhopper, wheelie dropper, slow speed bike handler to begin with and the short stays do help me on the tight, janky section of the trail at times.
As I said before, it's not bad, I just am conscious of needing to move forward more on flat, loose turns and wonder if something with just a bit longer chainstays would make me less cognizant of that need.
And then there's the whole size/scale issue. Bikes tend to be developed in their medium/large sizes, and the very large and very small sizes tend to be just scaled up/down - chainstay length is one of those things that don't get scaled - but the same is true of the wheels. A 29" wheel feels very different to a 5' rider than it does to someone well over 6'.
i never thought this was a large issue or grounds to take a stance on.
companies of all different brands have been trying to find the sweet spot and good on them. like commencal went to mixed wheel size and actually extended their rear on the meta sx by 10mm and shorted reach 10mm to find that balance. a balanced ride is a predictable ride, especially if it fits you properly.
Top Fuel Stack: 600
Stumpjumper EVO: 639 roughly
I also have a 2022 Top Fuel and damn does that bike corner. I'm impressed with it's handling characteristics, considering the travel and shorter length.
Insta: vessel_bike_project.
A lot of fun to ride.
This feels like the trail building equivalent of making every trail a flow trail. Although with 450mm+ chainstays that’s probably all the bike is good for.
I did not interpret the article to not be talking about DH bikes, I read it as Matt's attempt to start discussion about chainstay lengths on all mountain bikes.
Lengthening chainstay while keeping everything else equal will do the opposite of what you say and require less effort to pressure the front wheel.
I am tall and have long femurs and feet, it's likely that I am upwards of 5" further behind the BB when I bend at the knees than the average medium frame rider. I believe an XL or XXL frame should have CS >18mm longer than a medium frame. I have also noticed on my new 55mm longer reach bike that I need the bars to be significantly taller having to purchase the 76mm tall bars and higher rise stem to feel anywhere near comfortable while pedaling and descending. Stack heights should have much larger gaps between frame sizes (some brands keep stack the same from small to XL and that's just silly)
Without sounding a know it all, I knew all of this statement to be true for years now since bs intro of LLS.
Anyways... Must be a slow day in the cough office cough ;d
& A good day for tacobell eat in place lol
But hang on, isn't this what Paul Aston has been saying for ages now?
1) axle path. a long chainstay is one thing by itself. a long chainstay with a rearward axle path is a whole other animal.
2) rear wheel size. BB drop in relation to the rear axle has a tremendous impact on how the rear feels.
That said, the idea proposed of being able to select the CS that you want when you purchase your bike sounds great. I would be going 430 every time.
stupid auto-incorrect
Save your LBS and buy local; they exist so that you can ride a bike before buying it.
Somehow this writer has bike geometry fundamentally wrong (and gets paid for it), yet bike companies would have you believe that buying bikes blindly online is what's best. It's a lie: go, ride, find what's best for you, and support the local shop that enables you to do so.
Anyway, switch to using ***CS length & WB length*** for balance, and you'll be closer to where you want to be. WB length figures in the reach, HTA, and also fork length and head tube length.
A 435mm CS bike will lack rear traction if the WB is very short (less than 1210mm). A 435mm CS bike will lack front traction if the WB is very long (>1250). Going by reach and HTA is lacking, as this difference in WB could be entirely accounted for by the fork length and head tube length, with the reach and HTA the same.
There's also other things to consider like a high pivot's chain growth and rider weight. A larger rider will have more weight on the rear, which requires longer CS to offset. A size XL will have a longer WB, mostly from the increased reach and head tube length, which also requires longer CS to offset/balance out.
Easy to make simple predictions going by WB and CS. I predict that a 440mm CS bike's balance will feel pretty good with a 1250mm WB. A 445mm CS bike with 1270mm WB should feel well balanced too... for every 5mm CS change, add/subtract 20mm WB to get a ballpark figure. For example, a Commencal Meta AM 29 in size small has 433mm CS and 1231mm WB, which I predict should have decent balance. A Commencal Meta SX in size med has 442mm CS and 1253mm WB, which I predict should have decent balance. If I were between sizes, I'd might notice the size med Meta SX is maybe a bit on the racier side, coming alive if I let go and get my butt back, my back flat, and chin behind the stem cap, while a large Meta SX feels radder, more willing to get airborne, at cost of reduced front wheel traction that makes it more challenging to carry race-level speeds through corners.
Going off of rear center (horizontal CS length) and front center would be even more accurate, but virtually all geo tables have WB and CS listed. Don't do division/ratios, like with FC:RC, as I don't believe it works. Validate using scales under each tire, and finding the actual weight distro, trying to use consistent positioning from one bike to the next. I recommend a neutral stance, where you're balanced enough on the pedals to not need to use more than a pinching grip (between the finger tips of thumb and forefinger) to stay upright.
Suggestion for next article: "it's time to pick bikes more based on WB length, rather than travel amount." How do you feel about having a two-bike quiver, both with 130-140mm of travel, but one is 1230mm WB and the other is 1170mm WB?
when I say 'long' I'm longer then the modern Slope bike where the rear wheel is a close as it can be to the BB.
After coming across this, it's impossible to continue reading. Where is the glitch? Is the error in judgment, in print, in writing? What's going on? There is no dispute that the shorter the chainstay, the more the rider weight is concentrated on the rear axle. So is the whole article one long... fluke?
The rear can't oversteer by itself. OVERsteer means the whole bike is turning _more than expected_ for the provided _steering input_, and that input is the front wheel. So you need to consider both ends in any conversation about over- or under-steer.
That means more molds, more SKUs, and likely a slightly higher cost across the model range, but it means bikes will perform consistently for different size riders.
I can read a review of a Ripmo written by a reviewer who is 5'9" and riding a size medium and it will ride completely differently for someone like me, 6'6" riding an XL (true story, tried that). We look so closely at front center numbers, seat tube angles (I have another rant about "virtual" vs "actual STAs), and HTAs that the wheelbase and chainstay length are often overlooked until I'm moving up a techy climb and CAN'T keep my front end on the ground because my tailbone is behind the rear axle in the saddle. An XL Ripmo will not perform the way a medium will, rider and terrain proportionate.
Cost-saving by using the same rear triangle across a whole model range just degrades the experience as you move further from the peak of the rider-height/size bell-curve. Huge shout out to Transition, Specialized, YT, and Canyon (to name a few, reply with your favorites) for making a full size-range of bikes AND having AT LEAST two rear triangles to accommodate the range.
Maybe trying to get timed laps and measure performance from bike to bike is why geometry is so critical to you. I think lots of us are just out to have fun. And race spec doesn’t always translate to fun.
My 2015 Santa Cruz Tallboy almost killed me 50 times going down Whole Enchilada in Moab because of it’s 70°+ head angle and it’s 445mm chain stays.
So many drops into uphill faces- and I couldn’t wheelie off any of them! My 2021 Tallboy is worlds better all around, but still doesn’t like to wheelie on a steep downhill with it’s 445mm chain stay.
Luckily it doesn’t have a UDH, so I can shorten the chainstay for that ride. Go back to the long setting for most others.
CS should increase as the sizes increase, just to give the different sized riders the most similar experience of the bike (Stack should really also increase more than maybe 5mm, you can't tell me that the dude that is 6'4 only needs maybe 10mm more stack than the guy at 5'8, yes you can get higher rise bars to help with this).
I think that the most "playful" bike is the bike that feels the most balanced to you. At least IME then if you naturally have a neutral position on the bike (where both ends are weighed correctly), then it's very easy to throw your weight around and make the bike do what you want it to do.
On a sidenote, then being a XL rider I have for many many years delt with short CS that felt like I was seated over the rear axle and I am really happy that we have recently seen this wave of longer CS bikes
As nerdy as it can get, but still very interesting.
From full suspension bikes I had banshee scream, balfa 2stepHD, commencal supreme dh (the on Gee had one his first races on), Giant glory 00, kona entourage, rocky mountain slayer and altitude, specialized spumpjumper, santa cruz bronson, norco aurum 2 generations and I probably forgot something. The reach was probably 400-420 on all of them.chain stays were 450-something on supreme being the longest and entourage with 414 mm being the shortest.
I used to not care about chainstay length at all until an eye opening moment. I had a giant glory 00, chain stay was about 440 mm and I tried my buddy's demo, chainstay was 420. It was eye opening how fun it was to ride, it was nimble, but stable nimble. super easy to bunny hop and to turn. since the I had a kona entourage, chain sty was 414! super fun bike, check out reviews on that, even on larger sizes.
so, to summarize. there are theories being created about ideal chain stay lengths, how front end got longer so the rear end needs to get longer etc. but I do not trust any of that because people like to make up things and try to believe them. why have we been riding such short bikes for so long? there were theories about perfect geometry back then too. for me, it should not be longer than 430 mm otherwise it get really hard to manual and bunny hop if the reach is somewhere in the reasonable range.
For years I ride trails on a zero offset mountain unicycle.
People would comment on how it must be really “loose@ in slippery surfaces.
Think about it, a single contact patch, you’re centered over the wheel always, pretty much the most stable ride on a slippery surface!
I gotta laugh at sone of these king chainstay arguments, maybe folks need to spend more time driving off road so they get a sense for how a longer vehicle acts; ie Wrangler vs Cherokee.
When you watch Jeff Kendall swap between long chainstay bikes (I think he did it with a mondraker), he lost some of the pop that he likes to ride with. At some point there's a trade off with long FC (as shown in his article) but also with RC as well as Jeff pointed out a bit. Where should we be in that balance? I'm not sure, but it'd be nice if someone could fully test and modernize some of the stuff Lee McCormick did and start to standardize bike fitment. Cause as you saw in the article, the bike has stability but its coming with significant fitment compromises. I think we are over prioritizing stability a bit these days.
I kinda always got the same vibe from his reviews. He basically decides what he thinks is gonna happen before he's even ridden the bike, then approaches the review full of preconceptions. If the preconceptions don't fit the experience, then dammit the experience must be the thing at fault.
Hi Gabriel. The project is still going. It didn't "all fall apart around me" but it's great that you know so much about my life. There was never any money to start with, so it didn't really run out. It just got very very difficult when I spent lots (for me) of money on all different kinds of bikes and every single one of them broke.
I think it's a good concept overall and the business is starting to work despite the difficulties of starting this during cvid times, changing countries, buying a house in a foreign language etc etc. If all the products I had bought had worked properly then I would have had many more positives to say and nice things to sell - unfortunately I can't say things are good if they are not and sell them to people.
Maybe it's a mad idea, but someone has to try these things, otherwise, I would just be another paid-for independent reviewer getting paid 4-10k per subjective review. This option was fully on the table (and would have been much easier and more lucrative for me) before I decided to try and do something more positive for the consumers and the bike world in general.
I was planning and still am planning to do more objective work in the future, but without a big budget or backers it's hard - I'm trying to get some dynos and other machines for the future. I don't see much objective work from any online reviewers/sites regardless of how much budget they have. If you want to help out and create something really special we can do something together: I have the space, time and platform. You can bring a 50-100k investment and we can start with a couple of dynos and start measuring stuff. From there I have designs to build jigs to test frame flex, wheel flex and full bike testing jigs too. Plus the space to build specific test tracks where we can test bikes on exactly the same features with my Stendec, BYB, or AiM systems fitted.
There have been some big positives from my independent testing model, though, as multiple brands have already changed and improved things off the back of my work. Now some MTB consumers like you guys will get a better product! Woohoo, that's what I like to see.
As for me being full of preconceptions and changing my review experience to fit: I'm sure we argued about my testing process and methods years ago in PB comments. I seem to remember I invited you to come and visit me in Morzine and do some testing together? That invite is still open if you want to come to the farm in Italy: buy and bring some bikes with you that you would like to test, we can test and film them together for my channel, then you can keep them or we give them away in a competition and get your investment back? If this works well we can discuss the testing ideas above in person. DM me for my phone number if you want to discuss further.
Cheers, Paul
Banshee have done a running change on the Titan frame section I broke (and replaced my comp winners bike under warranty with no problems), though I think they knew that was an issue before.
Fasst Flexx are updating their website copy about bar geometry/suitability
Starling have modified/repaired all Spur frames
Unfortunately:
DT Swiss ignored me/the shop wouldn't comment on their broken shock.
Commencal and the top 15 MTB media (including this one) ignored me about Supreme frames cracking.
DVO, Fox and Ohlins ignored me publically about their products being shipped incorrectly assembled.
I'm sure there are some more bits and pieces too!
As far as bringing a load of bikes to raffle off after we've ridden them, (aside from my ethical concerns with the whole buy-to-raffle business model) I fear I wouldn't get anywhere close to my investment back. This is my worry with the whole arrangement really. I honestly hope you can make it work, but it looks like a money pit to me.
Apologies if I was mistaken about the project being over. I ditched FB and Insta a while back so haven't been following, but was told by a mate who's a big fan of yours that you posted on socials that it had all come to a end, and you were selling up due to financial issues. Glad to hear it if thats not the case.
Can you please straighten out this mess ?
Very much agree with all of this. The more articles you write, the more things I find we agree on. Keep on being right about stuff, cos currently yours is some of the best stuff on PB.