Opinion: Do We Need Size-Specific Chainstays?

Nov 2, 2023 at 8:13
by Seb Stott  
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A growing number of bikes are coming out with size-specific chainstays, and the effect that chainstay length has on bike handling is a major point of discussion in reviews. Size-specific chainstay lengths (where larger frames get longer chainstays) make a lot of sense intuitively - if the front-end gets longer, the back end should too, right?

But in some cases, the idea is in danger of becoming more of a box-ticking exercise than something that tangibly benefits the rider. Many of the bikes that offer this feature don't make a big enough change to noticeably affect the handling. And even for those that do, the ideal chainstay length for a given rider depends on so much more than maintaining some particular ratio of front-center to rear-center.

To understand why, we first need to talk about what effect chainstay length has on a bike's handling.

Ibis HD6 - Photos by Tom Richards

Chainstay Length 101

Also known as the rear-center, chainstay length is the horizontal distance from the rear axle to the bottom bracket. When you stand on the bike, almost all of your weight is on your pedals - only a small amount can go through your hands and the handlebars. This means the weight distribution between the front and rear wheels is largely determined by the ratio of the chainstay length to the wheelbase.

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For example, in the case of the Ibis HD6 from this year's field test, the size 3 has a chainstay length of 435 mm and the wheelbase is 1,256 mm (pretty typical numbers for a size medium these days). So, the chainstay is 34.6% of the wheelbase, which means 34.6% of your weight will sit on the front wheel and 65.4% will sit on the rear wheel.* In size 5 (effectively XL), the wheelbase is 1,328 mm but the chainstay remains at 435 mm, so the weight distribution becomes 32.8% on the front.

*I'm ignoring the suspension sag here (which affects the wheelbase and chainstay length) and the weight of the bike. This is a simplification, but it's close enough to get a sense of what's happening. I'm also assuming no downward force is going through the rider's hands, both for simplicity and because it's very hard for most riders to put a significant amount of force through the handlebar consistently. Try standing on your bike with your front wheel on a bathroom scale - it's surprising how much you need to lean on the handlebar to make a significant difference to the weight on the front tire.

That may not sound like a huge difference, but if you weigh 100 kg, then on a size 3 there would be 34.6 kg of force pressing your front tire into the dirt; on a size 5, there would be 32.8 kg. That's an absolute decrease of 5.2% load on the front tire. So, if you jumped from the medium to the XL without adjusting your tire pressure, fork setup or riding style, the front wheel would be less pressed onto the trail in the latter case.

But if we fitted longer chainstays in larger sizes, we could maintain the same downward pressure on the front wheel (for a given rider and body position) across the sizes. But how much longer?

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Scale Matters

Let's say we wanted every size of Ibis HD6 to have the same weight distribution as the S3 (medium). This implicitly assumes that the weight distribution is "ideal" in the size medium, which seems a little arbitrary, but let's go with it for now. Running the numbers, that would involve the S5 having a 473 mm chainstay (which is unheard of), while the S1 would need a 406 mm chainstay (which is unfeasible, as chainstays can't get much shorter than 435 mm without running into issues with tire clearance and chain angle).

In other words, the chainstay length would have to change by 15-20 mm per size to maintain a consistent weight distribution. To my knowledge, only Forbidden is getting close to that.

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YT Capra geometry

Looking at it another way, YT is one of the brands ticking the size-specific chainstay box with their Capra, but their chainstays only grow by 5 mm across the range (438 mm for small to large & 443 mm for XL and XXL). On the XL, the weight distribution would have been 34.4% on the front if it had the same (438 mm) chainstay as the smaller sizes, but the longer chainstay changes that to 34.7%. That's a difference of 0.3% of the rider's total weight, or the absolute amount of load on the front tire goes up by 0.7%. Despite the change in chainstay length, the small still has 7% more front tire load than the XXL.

In short, it's a token effort. But it's not just YT; most brands currently offering size-specific chainstays are only making tiny changes - the Yeti SB160 changes by 2 mm per size, which doesn't seem worth the effort to me.

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How Does Chainstay Length Affect Cornering?

Okay, so making the chainstays much shorter on small sizes isn't feasible, and making them 5 mm longer on the biggest sizes doesn't do much, but maybe making the chainstays a lot longer on bigger sizes is worth doing. After all, head tubes can't be made any shorter than about 100mm, so many bikes use the same length head tubes on XS, S and medium, but the large and Xl still benefit from bigger head tubes. Could we see a similar approach with chainstay length, and if so, would that improve cornering traction?

Making chainstays longer in an XL will result in more pressure on the front tire for a given rider position, but how this translates to reducing the risk of washing out in a turn is more complicated than you might think.

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To illustrate the point, let's take things to extremes and imagine you have a bike with a 25:75 rearward weight distribution and another with a 50:50 weight distribution. Just for context, that would be like fitting our S3 Ibis from earlier with a back-end that was either 270 mm or 820 mm long.

Again ignoring the weight of the bike, sag, and any weight on the handlebar, and assuming a 100 kg rider for easy maths, there would be 25 kg of downward force on the front tire for the first bike, while the second would have 50 kg on each wheel.

You might think that since the second bike has twice as much weight on the front tire, it will have twice as much front-wheel grip, so you can corner twice as hard without the front wheel sliding. But that's not the case.

This video explains why a rearward weight bias requires more lateral cornering force from the rear wheels and less from the front.

Imagine going around a big flat turn with a constant radius at a constant speed (this is called steady-state cornering). The friction between both tires and the ground provides a lateral force towards the inside of the turn (called centripetal force) that keeps you turning and stops you from heading off in a straight line. If you have a 50:50 weight distribution, so the centre of gravity (COG) is halfway along the wheelbase, both tires provide an equal amount of this lateral force. If you have a 75:25 rearward bias, so the COG is 75% of the way along the wheelbase towards the rear, then the rear wheel must provide 75% of this lateral force, and the front wheel only provides 25%. This is because, with the COG closer to the rear wheel, there's a shorter lever arm between the tire and the COG, so the rear tire has to provide more lateral force to keep from sliding out.

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But the front wheel also has 25% of the vertical load (weight) and the rear has 75%. You may remember in high school being taught that the friction between two surfaces is proportional to the force pressing them together. So, the bike with the 25/75 weight distribution has half the load on the front tire, so it can produce half the lateral force compared to the bike with a 50/50 weight distribution. But with the COG closer to the rear axle, the front wheel only needs to provide half as much lateral force to get around the corner. This means that if lateral grip is proportional to vertical load, then these factors cancel out and both wheels will be equally prone to sliding. In other words, the bike with the rearwards weight bias isn't more prone to understeering (front wheel sliding) than one with equal bias.

Does this weight distribution doesn't matter? Unfortunately not.

A weight distribution closer to 50/50 is better for cornering because of something called tire load sensitivity.

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In reality (despite what my physics teacher taught me) grip usually isn't proportional to vertical load. On hard surfaces, such as asphalt, the ratio of grip to load decreases with increasing load. In other words, if you double the load on the tire, the grip it can provide is less than double. So, in our extreme case of a 75% rearward weight bias, it's the rear wheel that would be more prone to sliding, not the front, because it has to provide 75% of the lateral force but it has less than 75% of the available grip.

In contrast, on soft surfaces like mud and sand, the ratio of grip to load generally increases with increasing load, so if you double the load on the tire the lateral grip will more than double. Thanks to Steve Matthews of Vorsprung Suspension for pointing this out to me and sharing his knowledge more generally. So in this case, a bike with 25% of its weight on the front wheel will have less than 25% of the available lateral grip, so it will be most likely to slide.

03.06.21. Pinkbike BikePark Wales Rider Seb Stott. PIC Andy Lloyd www.andylloyd.photography andylloyder
The Forbidden Dreadnought does size-specific chainstays properly, with a 464 mm rear center in size XL that grows to around 480 mm at sag. When I reviewed it, this delivered downsides as well as upsides.

Putting it All Together

So to summarise, getting closer to a 50:50 weight distribution helps the bike to handle more consistently. Otherwise, either the front or rear wheel could be more prone to sliding out, depending on the terrain. It's not as simple as saying that having too much weight on the rear wheel will always cause the front wheel to wash out more often. It's certainly not the case that getting X% more load on the front tire will allow you to corner X% harder.

While this article has already gone on long enough, there's still much more to this topic, such as the ability of the rider to actively lean on the handlebar or the effect of braking to move the weight distribution closer to 50:50. Then there's the fact that most bikes use different tires on the front and rear - having a stiffer tire casing on the rear with a more aggressive tread on the front can somewhat compensate for a rearward weight bias. Also, people on smaller sizes generally have more upright riding positions and those on larger bikes have more forward-leaning riding positions due to a shorter stack height relative to reach, so the rider's weight will generally be further forward relative to the bottom bracket with a larger frame size.

Raaw Madonna V3
We're seeing more bikes with adjustable chainstay length, usually with 10 mm to play with.

The main point here is that you need to make the chainstay a lot longer to get the weight distribution a little bit closer to ideal. As a rule of thumb, you'd need to add 15-20 mm to the rear center per frame size if you want to keep the weight distribution the same. A 5-10 mm difference across the entire size range isn't doing much. Adding 10 mm to the chainstay length will only move the weight distribution of a typical bike from around 34% to 34.5% on the front (ignoring rider input).

In the past, I've tested several bikes with chainstay lengths that are adjustable by 10 mm and hastily written that I can feel a difference and prefer the longer setting. But thinking about it more deeply, extending the chainstay by 10 mm will increase rear-wheel travel by around 2.3% and reduce the spring and damping rates at the rear wheel by around 5%. If you don't adjust the shock settings, this is the main difference you'll notice. Not only that, with a 10 mm longer chainstay there will be about 1.5% more load on the front tire for a given riding position. While this difference is probably negligible, in theory, this extra load will add to the risk of tire squirm, burps and dings, so it should be compensated for by increasing the front tire pressure by a similar percentage. Otherwise, the effect is similar to running the tire softer, which will increase grip when the tire is lightly loaded, but increase the risk of squirming when it's heavily loaded. If the suspension settings and tire pressures are adjusted to compensate for these considerations, the advantage of a longer chainstay will be diminished.

In contrast, if you get your weight forward in a flat corner by leaning on the bar, you're temporarily adding load to the front tire, so it's heavily loaded relative to the tire pressure and generating good grip, but you can revert to a more neutral/rearward position in rock gardens and berms to prevent tire squirm or burping. In other words, increasing the chainstay length is not the same as riding with an aggressive body position.

With dramatically longer chainstays (such as the XL Forbidden Dreadnought with a rear center that stretches to 480 mm at sag), I think the weight distribution is noticeably better in flat turns, but there are downsides to consider too, including a shallower breakover angle (assuming the BB height stays the same); a tripping sensation on steep, technical sections; and a slightly longer overall wheelbase which requires more steering input in tight turns.

But the main drawback people notice with long chainstays is that they make it harder to manual. To lift the front wheel off the ground, you need to get your center of gravity behind the rear axle; moving the axle even 10 mm further back makes it noticeably harder to do this, and that can be a big problem for some riders.

Greg Minnaar
The GOAT appeared to be running his XL V10 in the shorter chainstay setting at Fort William this year (456 mm) despite experimenting with longer rear centers recently. Either way, it's nice to have options.

What's the Bottom Line?

So, in an ideal world, I'd suggest picking the longest chainstay that still allows you to manual comfortably. In general, this rule of thumb would mean taller riders running longer rear ends, but it also depends on the rider's weight, skill, and cockpit setup, as well as how they prioritize consistent grip versus ease of lofting the front wheel (racing versus jibbing). It's not about hitting some magical ratio of front-center to rear-center, because there's nothing magical about that ratio in any frame size, but rather that riders who have no trouble lifting the front wheel may as well benefit from a more balanced weight distribution and the more consistent grip that goes with it.

Forbidden's latest Supernought has a 20 mm adjustment range in addition to size-specific rear-ends, which I think is a great approach.

Adjustable chainstays are better than size-specific ones because riders can choose what works for them based on many factors including terrain and personal preference - not just frame size. But remember that the 5-10 mm adjustment that's currently being offered isn't going to make a big difference to weight distribution. It would be interesting to see a larger adjustment range (at least 10 mm in either direction) become available, perhaps in combination with size-specific back ends, but I wouldn't be surprised if some tall riders still prefer a more conventional chainstay length.



Acknowledgements

Thanks to Steve Mathews of Vorsprung Suspension, Dave Weagle and Joe McEwan of Starling Cycles for their help and advice with this article. While the opinions above are my own and don't necessarily reflect any of theirs, their insights were invaluable.

And of course, thanks to Taj Mihelich for the illustrations.




Author Info:
seb-stott avatar

Member since Dec 29, 2014
298 articles

289 Comments
  • 149 2
 Always thought that more companies should have taken an approach to bike rear ends like Banshee did. Modular dropouts with different lengths and heights to really free up options for the consumer, and for the aftermarket too. Keeps bikes going longer too if they're not stuck to a hub standard / wheel size.
  • 5 1
 Exactly. Or like most higher end hardtails that are built with SS or belt drive options. A modular dropout could deal with chainstay length adjustments as well as mullet wheel options.

Only issue with adjustable ones is that I believe there recently was a bike released that was adjustable (flip chip I think) but it could only run Transmission in the rear position. Probably just modular/replaceable ones would be best, plus it means bike makers can sell more stuff!
  • 61 0
 The Banshee dropouts are so versatile. Want to run mullet? You can do that. Want to run 29+ tires? You can do that. Have an old non-boost wheelset you wanna run? You can do that. It's such a simple design I wish more manufacturers would embrace.
  • 5 1
 Agree 100%. I have 425mm chainstays on my Tilt. 440mm chainstays on my Transition. Both lengths have their advantages. But it would be so nice to switch it up to suit the type of riding I'm doing. Even if it's just a 10/-10mm swap.
  • 3 0
 Salsa does the same type of thing..or did.
  • 3 3
 electronic adjustable on the fly rear end next?
  • 5 0
 I am more the "ride what ya got" kinda person, but adjustable CS's make the most sense to me.

If I want to do a 5 mile ride with lots of tight twisty stuff I could see shortening the rear end up.

Iff I'm going on a 40 mile (long for me) ride where I know I'm going to be exhausted, and won't be trying to throw the bike around every turn as fast as possible, then lengthening the cs' would be nice, plus the added stability on climbs and descents would be great. . . it would also be great if you could change CS without effecting bb height at the same time!

Or you can just get a bike that's somewhere in the middle and learn to live with what you gots. . .I guess.
  • 12 0
 Geometron also allows you to choose your chainstay length with its mutators. It's a fairly simple and elegant solution to give choice to the owner.
  • 5 0
 In addition, you can offer dropouts for upcoming standards like UDH or whatever „the industry“ is introducing in a couple of years. I am pretty sure, that Banshee will offer some UDH dropouts for its bikes in the near future.
  • 11 0
 I sell banshees.....and some other ridiculously boutique bikes. hyperbikes if you will.....and the banshee is the one that I keep going back to for the smiles per dollar factor. it's $7000 spec'd to the moon, and I don't think it's any slower than the $13,000 bikes I sell.

Love Banshee!
  • 7 1
 Exactly, because not everyone wants to run the "correct" size chainstay. For example I prefer short chainstays because fun is fun and they suit me and what I ride, and other people want to experiment with their size as well.
  • 1 0
 I'm a big fan of the adjustability of such systems. The problem is, in a world where low weight is chased so hard, they do add weight and that weight is added at an awkward place. It's such a small weight penalty it's a no brainer for me, but I've no doubt most bike marketing depts would think that the lower weight is a bigger selling point.
  • 1 2
 Size specific chainstay are a must.

Modular chainstays are also a must in combination with size specific chainstays.

So far, the issue was: Tall designers used to built bike with long chainstays amd small designers used to built bikes with short chainstays…… selfishness!
  • 2 0
 @High-Delberg: just talked to Banshee and they can't do UDH dropouts with the current triangles.
  • 3 0
 I have a 2014 banshee Rune that came with 135 dropouts. At the time, why the f*ck would you want 27.5? But it was there.

I did buy the 142 dropouts but last summer I destroyed my wheel at silver Star and the only spare I have is 135 so, change the dropouts.

And of course the 142 /27.5 dropouts are longer and I can feel the difference when trying to manual but at the bike part it's definitely more stable. Modular is the way to go
  • 2 0
 @velovirtue: I doubt it. There is a dude who 3D printed titanium dropouts for UDH. Banshee provided the measurements. Check @en_j_oy_life_ on Instagram.
  • 3 0
 @Mtbdialed: great to see a budget bike with high end performance.
  • 1 1
 @NoahJ: your riding slower with short stays, youd trust your front contact patch more with longer stays, IF your pushing that hard.
  • 2 0
 @englertracing: most of my riding is ridges chutes and jumps with jumps being my priority. So while longer would be better when I go out for a DH ride and probably for ridges as well there is a reason every free rider runs shortest stays they can
  • 1 1
 @NoahJ: oh like when remy ran 29 stays on his tyee 5 and spindrift mullets, even though it fkd his bbh.....
to get a longer chain stays...
i suppose when your riding below your limits, and shralping and playing short cs feels more playful, but at full on where your tiptoeing around ever so slightly exceeding and smoothly correcting front end wash the longer chainstay loads the front end up.... and everyone thinks its just 5mm but its got around 1.8X the effect of 5mm change in front center.
  • 1 0
 @englertracing: I wasn’t referring to remy when I said freeriders, he might be one to an extent but I meant classic freeriders like zink, Storch etc, even straight who is more loose runs short stays. I totally agree with you that longer stays are better for riding trails especially rough ones. But I wouldn’t consider back flipping to be riding below my “limit”. I just choose to push myself In different ways than you do and as such short stays benefit me and if like the option of running them.
  • 1 0
 @englertracing: I’d say every bike should have adjustable stays so everyone can get what they want!
  • 87 19
 NO! Its personal preference. Im a tall guy but I like a nice short chainstay. Geometry is a personal choice. Some people like short responsive playfull bikes some like long stable bikes.
  • 17 1
 I’m assuming you’d like to have an axle flip chip? You’d run yours short, I’d run mine long. Everyone wins!
  • 5 0
 Yes! I’m a tall guy, I’ve ridden both and decidedly prefer a proportional chainstay on my XL bikes. It is personal preference, good thing we have options!
  • 1 0
 @joecrosby: I’d run mine long too Joe!
  • 12 3
 I'm on team long/proportional chainstays personally, but I agree, its also a preference.

I would love for modular dropouts/chainstay length flip chips to be more common.

However, I think that SRAMs new Transmission is making life hard on flipchips, because of how the deraileur mounts to the chainstay. Most of those only work with transmission in the longest position (RM Altitude is like this), or not at all (Raaw Madonna has a Transmission specific seat stay).

I'm worried we'll see less chainstay adjustment here in the near future as brands are racing to support the newest bling (like, the RM Altitude/instinct models, Kona Process X, etc).

As a Banshee owner I'll say "MORE DROPOUTS" (Also, see Kavenz V2, another good recent example).
  • 2 1
 But you're not answering the question at hand - should they be size specific. You can still have relatively short chain stays for a given model of bike, but have them size up through the range.
  • 4 1
 Im with you on that, im a taller guy but i prefer shorter chainstays on my bikes. I understand longer chainstays are more stable, but that not how i like to ride. flip chips would be a good compromise though.
  • 19 5
 I’ll take my chainstays as short as possible, thank you.
  • 13 2
 Seriously, not all tall people want long back ends... I think giving people choice in the matter is really nice. I too am tallish (6'2) and love the shortest chainstay/ smallest bike I can still comfortably pedal all day. I want my bike to manual and hop with ease. Everything else does not matter to me. I'm tryna jib off everything! long bikes just feel so stuck to the ground without a lip or bump to help them out. I get some people prefer stability; that's just not me (not really racing these days and slowing down more every year...).
  • 1 1
 @willdabeast410: I think today's market already provides that, with different designs being focused on different things (shorter, in between, longer). That that doesn't mean that the chain stay length needs to be the same across all sizes, which provides a different experience for different sizes of people on the same bike.
  • 1 0
 QFT!
  • 4 2
 I'm with you. 535mm reach, 697mm stack, 435mm chainstays on my custom bike. I can still out corner most of my friends even though this front to rear center balance should be unrideable.
  • 4 0
 Here is an already older article in german that tackles the same topic... it is highlighting thepart about the rider and personal preference a little more in my opinion. However most conclusions seemingly haven't changed too much during the last 4 years.

www.mtb-news.de/news/forschungsprojekt-mountainbike-geometrie-3-8-was-ist-die-perfekte-kettenstrebenlaenge/#Sinnvolle_Gruende_fuer_kurze_Kettenstreben
  • 5 0
 Give the ability to swap chainstays. Get an XL bike with Small chainstays if you want.
  • 8 1
 It’s personal preference and not much else. As far as any “calculations” go, I’m always surprised how willing they are to imply an entirely static rider - no comparison to, for example, cars has any relevance whatsoever.

My personal preference is also for short chainstays. Nothing against size specific ones, if they start at 415 mm for a size S frame and or no longer than 435 mm for an XL.
  • 1 0
 This.

I’m 186cm / 6’1.5” and 440mm chainstays are my sweet spot.
  • 2 1
 This. Bike companies should just give us the adjustability so that everyone can run their bike the way they prefer.
  • 3 6
 I am willing to bet that your stack/bars are too low for your height so you favor a short chain stay to compensate.
  • 6 0
 yup, agreed, i prefer the bmx freestyle method, shorter the better. currently on 510 reach with a 430mm chainstay, works just fine, but i'll go shorter reach next time for more fun-ability
  • 3 0
 @haen: i'm willing to bet all your bike geometry and fitting experience is rooted in pinkbike articles and not from years of experience
  • 1 0
 @hot-beef-sundae: what’s the highest you’ve run your bars?
  • 3 2
 @haen: a frame with a higher stack will actually have a longer front centre than another bike with the same reach number and lower stack. So basically as you raise stack, you would have to keep making the chainstays longer if you follow this philosophy.

Alternatively if you create a higher stack with stem spacers you are shortening the bikes reach, so you would then need to shorten the chainstays (following this philosophy(
  • 2 0
 @ponyboy24: all the points you raised are correct.

If you raise your bars, you dont necessarily need to maintain as long of a reach. You can keep the same front to rear ratio.

In broad terms, if your bars aren’t as high as your seat at full extension, your bars are probably too low. Short chainstays help compensate for a low front end.

You should read this thread for a more detailed discussion on this.

www.vitalmtb.com/forums/hub/general-cockpitcontact-point-discussion
  • 3 0
 @ponyboy24: Then there is bike I just finished 415mm chainstays and all the rise with S&M Husky 4 speed bars (6.25in of rise). I love it.
  • 2 0
 Add another tall guy that likes a playful bike , thank you
  • 2 0
 @fastback570: I think there is a lot of us!

Tall guys don't necessarily want Bikes with crazy long wheelbases that can't get around corners.

Nor crazy long chainstays that take away all dynamic handling characteristics like being able to lift the front wheel off the ground
  • 66 0
 "I'd suggest picking the longest chainstay that still allows you to manual comfortably"
By this logic, I'm stuck riding a unicycle.

As always, great article @seb-stott.
  • 3 0
 If you try to manual a unicycle, you'll trip. Unless you rest your feet on the crown, obviously.
  • 8 0
 @vinay: I'm confident I could manual a unicycle just as well as I can manual my trail bike
  • 1 1
 @FensterM: That's impressive indeed (unless you can't manual a trail bike either). I can ride a unicycle (off road), but I'm not on the level that I can manual it.
  • 8 0
 @vinay:...I can't manual either. I'm not very good at riding bicycles.
  • 8 0
 @vinay: whooooooshhhh
  • 2 0
 @FensterM: underrated comment here.
  • 1 0
 @vinay: how much more practice do you think will be required before you can overcome the laws of physics and levitate your unicycle over the clever jokesters below?
  • 3 0
 @justridingalong1: Oh yeah, that was a wooosh most definitely. @shortcuttomoncton : Don't hold your breath Smile .
  • 1 0
 I guess we all gonna get bmx bikes now
  • 44 1
 Interesting analysis, but all of the math was on flat ground. Take the Ibis S3 example from above. On flat ground, you have 35% of your weight on the front wheel. On a downhill 10 degree/17% slope, that jumps to 46% of your weight on the front wheel. Add a little braking, and the front wheel will easily go over 50%. All of this requires a lot of assumptions about the center of gravity of a rider, but it looks like chainstay length has very little impact on front/rear weight bias compared to actively moving your body position and the slope of the trail.
  • 1 1
 Agreed. Keep short chain stays if you like for straight line functions and performance and lean forward more in attack position, with outside elbow high in corners.
  • 3 0
 Came here to say this! But interestingly I find that longer chain stays do have quite the influence on climbing of a bike and how much you have to lean forwards.
  • 5 3
 and the steeper the trail gets, the more likely most riders are to have a rear weight bias. which means long chainstays are to compensate for lack of skill on the rider's part, stay committed, stay formward, go fast, have fun
  • 3 0
 @Muscovir: All of the math was assuming a static weight distribution in the first place. While this is fine for cars, where the rider will be entirely static and typically represents less than 10% of system weight, on a bicycle the rider has quite a range of motion and typically represents closer to 80% of system weight.

Moving you hip forward or backward by five centimetres (and your maximum range to do this is probably about 30 centimetres or more) will have a similar effect to a proportionate change in chain stay length - and as stated in the article those often change only by 5 millimetres (not centimeters) over different frame sizes or between manufacturers.
  • 26 1
 I think the angles we ride bikes on (up and downhill) make for so much more of a perceptible geometry/weight balance change than any reach or length adjust mechanisms could do. Exercises on paper on "level" ground are pretty quickly out the window on actual trails.
  • 10 0
 Agreed, and seconded! All Seb's assumptions and weight biases are based on flat ground. As the trail gets steeper downhill, the CG is pushed forward between the wheels, and the weight bias goes more towards neutral. Any trail steep enough to front-bias your wheel feels awful (feels like you're about the go over the bars) and you change your setup/geometry/length of bike to adjust until it feels comfortable again. Then you ride a steeper trail, and repeat.

I've found with suspension data acquisition that your normal weight balance on a DH is more or less 50/50, and you adjust your bike setup but mostly your body position to achieve that. It happens automatically, and modern geos just let you achieve that ~50/50 position without contorting yourself too much.
  • 5 0
 Yea, not only is terrain constantly changing in angle, camber, roughness, and traction, but as the level of rider performance increases, the more the bike gets unweighted, popped, and pulled up and over rough sections. "racing versus jibbing" makes it sound like racing = static plowing, which no one is doing successfully at advanced levels. Sometimes intentionally breaking traction to hit a catch point is the fastest way around a corner. Modern mountain biking is much more dynamic than static weight flat cornering, the bike is closer to a pair of skis than it is to a vehicle.
  • 6 1
 Yep, he over simplifies in order to cherry pick for the argument he wants to support. People also seem to ignore the impact of reach on unweighting the front wheel. Long front centers have just as much impact on moving your center of mass rearward as the chainstay length does and pull your weight forward in steep terrain. Especially when braking. Being able to respond to obstacles in steep, technical terrain requires the ability to lift and move your front and rear wheels.
  • 6 0
 Most of these pseudo-scientific pieces are simply ruled out by Betteridge's Law of Headlines.
  • 16 1
 I once owned an XL Canfield Riot. It was fun, but I'm 6'4" and the chainstays were 414mm according to their website. I looped out trying to jump over anything so many times it was scary. Fun for cornering sure but a bit too extreme for my size so yes, they are necessary.
  • 5 0
 Same here. Also 6'4 on an XL Riot. Super fun, but climbing anything close to steep meant almost guaranteed looping out. (I suppose it didn't help that I up-forked to 160mm, but still...). Still a ton of good times on that thing while I had it.
  • 15 0
 @jsnfschr: I upforked to 160 too! Did we just become best friends?!?
  • 5 0
 @Tmackstab: Maybe you have Multiple Personality Disorder and both of these posts are from you? It's not like you would know!
  • 3 0
 @SunsPSD: just commenting to be able to read as this thread develops...
  • 1 0
 @Narro2: Bump
  • 3 0
 @Tmackstab: Oh snap. I bought my frame from you! Ha ha ha ha.
  • 5 0
 Is there a circle jerk coming soon?
  • 5 0
 @Monkeyass: I think everyone in a circle jer… ah never mind, too easy.
  • 2 0
 @jsnfschr: lol!!! is that for real? is it true?!!
  • 7 0
 A Canadian bromance. A better love story than Twilight ever was.
  • 21 2
 Pick a chainstay length and be a dick about it.
  • 1 1
 Absolutely. Lol.
  • 2 1
 Was specifically scrolling through looking for this comment. Saved me the trouble.
  • 1 1
 @preston67: Happy to oblige.
  • 19 3
 Yes
  • 8 1
 No
  • 6 1
 Maybe
  • 6 1
 So?
  • 5 1
 I don't know
  • 9 1
 I disagree with you all
  • 2 0
 @GFozzz: Agreed.
  • 1 0
 @GFozzz: You’re wrong.
  • 1 0
 Ah, Is this the right room for an argument?
  • 1 0
 @acali: Oh yeah, please make yourself at home. Make sure you disagree with everyone and agree with some.

@GFozzz @FuzzyL : You're equally correct.
  • 1 0
 Can we start personal insults and name calling yet or is it too early?
  • 1 0
 @panaphonic: Everything has already been said, but not by everybody yet.
  • 1 0
 @FuzzyL: Everything. There, I said it.
  • 1 0
 @vinay: Ok, then @panaphonic can start the name calling now.
  • 14 5
 I don’t want to be mean here but this article isn’t your best work Seb. There are so many vital considerations that need to be taken into account here that weren’t.

For example when you lengthen the chain stay on larger size bikes you’re increasing the leverage on the shock. Do we really want different size bikes to have a different leverage rate? Also your largest (typically heaviest) riders would have MORE leverage, which isn’t desirable. The caveat here is some frame manufacturers address this by moving the BB and pivot points in the main frame to increase the rear center while keeping the chain stay the same physical part across all sizes. There are manufacturers that choose both approaches. This should be covered in your article.

Also, for a sport based around downhill you can’t evaluate based on flat ground assumption especially for a sprung vehicle. There are just way too many factors left out here. If this was a fully rigid road bike sure this simple analysis is probably sufficient but for a MTB it’s too simplistic imo.
  • 3 0
 Ignore suspension.

@SebStott shouldn't have even bought this up in the article. Geo should first be considered on a rigid bike to get the dimensional proportions "correct" or as the designer intends them.

The suspension kinematics can be sorted once the dimensions are sorted. Trying get to do both at once throws too many variables into the mix.
  • 8 2
 I don’t see how your criticisms would invalidate any significant part of the article. Of course one could expand the scope and talk about a myriad of things related to chainstay length.
But none of it changes the central point of the article: Size specific chainstay lengths as implemented by most brands have negligible effect on bike handling. And non-size specific chainstays are not necessarily a drawback.
  • 8 0
 Yeah, sorry, I'm gonna nitpick:

"You'd need to add 15-20 mm to the rear center per frame size if you want to keep the weight distribution the same."

This doesn't seem right. Usually the difference between sizes is around 25 mm. With chainstays being one third of the length, their proportional increase per size would actually be under 10 mm.
  • 1 0
 Something seems off with his math. Somehow he ends up with an 820mm rear end for 50/50 weight distribution???
  • 1 0
 A lot of people think that a rider's center of mass is somewhere around the hips. Because seatposts are not vertical, the rider's weight moves back relative to bb as frames get taller. Front end to rear end length ratio is different from weight distribution front to rear.
  • 2 0
 @FatSanch: You're right, that's another one.
  • 1 0
 @uponcripplecreek: I know what you mean, but Seb specifically talks about "all weight on the pedals" scenario, so front-center to rear-center ratio equals weight distribution.

He later even argues taller riders tend to have a more forward-leaning stance due to relatively lower stack, which sound plausible. But that would be the opposite effect of what you're saying, so I still don't know how he came to the 15-20 mm number.
  • 1 1
 @paja-tousek Hate to say it, but I think your math is the math that's a bit off.. Chainstays being 1/3 the length of the reach? You are getting confused with reach and wheelbase. My bike has a 480 Reach and 448 CSL. If the reach grows 25mm (to 505mm) the proportional CS would need to grow 23mm to 471mm. 448/480=471/505
  • 1 0
 @misteraustin: But that calculation is also off. The center of mass is not where the chainstays end, and a change of weight distribution between frame sizes is not solely influenced by the change in reach, so calculating the chainstay length based on reach alone will never work.
  • 1 0
 @misteraustin: I never said reach, but I should have specified that I'd meant length as in the length between wheel contact points, i.e. wheelbase.

Also, watch out that not just reach changes between sizes, also headtube lengthening contributes to the overall wheelbase difference between sizes. I assumed the wheelbase differences between sizes would stay similar, but would be distributed between reach, headtube and chainstays changes.
  • 8 1
 Absolutely yes, make the rear centre ratio more consistent, but it's personal preference and can be taken too far.

At 1.93m tall I prefer a longer rear but have also enjoyed bikes with a short rear end.

I do find the ~2mm difference per size by some brands to be a token / joke effort, but I'm not a bike designer or engineer so what do I know.

STA , stack, ETT all play into it too.
  • 4 0
 This is where manufacturers will have their preferred F/R ratios and you pick a manufacturer to suit your preferred handling.
  • 11 1
 It's good to have a choice. For example, I like wearing extra small speedos.
  • 8 2
 "But the main drawback people notice with long chainstays is that they make it harder to manual."

And benefit for right sized chainstays is a more comfortable riding position on steep, technical terrain. A well balanced front:rear center ratio means you won't loop out AND you don't have to eat your handlebar when climbing. This is probably why you don't see stack grow proportionally with reach on larger sizes, especially when stay length doesn't increase significantly, or at all. If it did, the rider's weight would be shifted even further back while climbing in a neutral position, requiring the "eat the handlebar" position on lower grades.
  • 16 7
 Hear me out,
There is no "right sized" we, as humans are incredibly adaptable, as noted in the earlier comments, Peaty, MInaar, and Chausson of 20 years ago would still destroy you, and 99% of us on their 26" wheeled bikes, that were super short. Its not holding you back, you, are holding you back, and you, along with all of us become obsessed with pointless details as the "reason" for this and that.

People are all different, ride different trails, on different terrain, with different styles and abilities. There is no "right sized" for everyone, which is why its great that theres so much variety out there
  • 6 0
 @onawalk: I agree with what you're saying, people are shockingly adaptable (and 90% of bike setup conversations are faff), but are you suggesting that people are so adaptable that there's no point in ever thinking about, talking about, or developing bicycle geometry and setup? Because that's what it sounds like, and that seems like a stretch.
  • 3 0
 @onawalk: The geometry of the Orange bikes these men rode back then were quite up to date (to modern standards) actually. Not sure about Commencal. For the Athertons they made quite long really but they deemed them impossible to ride for their customers so the production bikes were a good bit toned down. Wouldn't be surprised if ACC also received something special. The Athertons were still legends in the making back then, ACC already was a legend (just lacking the first ever Olympic BMX gold medal at that point).
  • 3 1
 @onawalk: Ok, maybe I should have said the inverse of the quote in the article instead of the word "right"; "And the benefit of longer chain stays...etc". Aside from the semantics of the one word, the rest of reasoning is objectively true. I'm also talking in the context of climbing. The pro's you reference are in the context of DH, so I'm not sure of your point other than arguing that I used "right" vs. "longer" (pointless detail?). No sh*t a pro will destroy a non pro.

Sure, agreed people are adaptable. They adapt to short stays on steep climbs by "adapting" into a "eat the handlebar" position. I'd prefer to obsess with my "pointless details" that are an objective cause for an adaptation I don't need to make on my person and leverage the available variety that you're touting so my bike is more comfortable to ride.

I'm also pretty sure one of the main points of the article is that there isn't much effective variety in chain stay length out there when you look at the actual different ratio deltas between sizes.

Also; "it's", not "its". Sorry, but details matter.
  • 5 6
 @onawalk: you’re that clueless dude that is way too confident about things you don’t know about.

Your entire statement is baseless and fallacious with the only semi-factual thing being that different trails are different.
  • 2 1
 @TEAM-ROBOT: Theres benefits to all sorts of things, what there isnt is a benefit to is deciding (based on nothing other than opinion) that what you believe is "right" and that all others are wrong (wheel size, flat vs clipless, sizing numbers, etc)

In fact, I think im advocating for the exact opposite to what youre suggesting, I just think that we need to be more open to the idea that there is no "right" theres just "different". For different people, places, trails, styles, etc.

Mainly my point was that very little of the things we as mountain bike enthusiasts obsess about is either holding us back, or has that large an impact on our overall enjoyment. In fact, we seem to lean into every little detail as reasoning to why this, that or the other thing is better or worse, and defend that position with impressive vigour.
I just think we should move away from the hard and fast ideas of what we think is "right" cause its not a one size fits all.
  • 2 1
 @vinay: I mean a first and second gen V10, had a 67* HA, and a wheelbase much shorter than 1200mm in a size medium. I dont think thats close to todays numbers.

All those mentioned were spectacular riders, but did so with much less faffing around than today. I wonder how those riders would do in the DH WC field of today?
  • 3 1
 @robporkbelly: Apologies, wasnt trying to offend.

Hear me out, the idea of what you believe is "right" or prefer, or whatever might suit YOU while climbing, but might not suit another while cornering, or while descending. With most modern trail bikes being asked to excel on so much, on such varied terrain, under vastly different riders, etc, ones preference for a longer, or size specific chainstay might be exactly the opposite of what someone else is after.

For me, and maybe I'm alone in this, its all a compromise, every little detail is a compromise in one way or another. Whats right for me climbing, has its drawbacks on flatter sections or the descents. I'd almost prefer to walk up than trade off some of those details, again, we are all different, and what suits me might be unacceptable to you, and thats cool.

The idea of an additional 5-10mm of CS length is going to make or break a ride is comical to me, but that might ruin your ride, and thats a bummer, cause I want you and everyone else to have a great time when they are out pedalling around.
We are never going to experience the same trail the same, and the pursuit of that seems like a fools errand to me (hell I dont experience the same thing every time I go riding) We all excel at different aspects, have different levels of skill and fitness, and prefer different types of trails. How would 10mm of CS change that, and why on earth is that the goal?

All that being said, if YOU want additional CS length, friggin cool, i dont judge in any way. If you want to feel more comfortable when climbing, thats awesome, go after that.

What I dont want is every bike manufacturer to think this is the way that things "have" to be. We are trying to make a recreational activity in the woods too specialized, and that makes it more expensive, and puts it out of reach for lots of people, and thats a shame.

My computer doesnt bother to add the apostrophe automatically, and I cant be bothered to go back to change it.
Some details matter, most are just something to obsess about, and eventually become points to argue about, and in the context of recreational activities for adults in the woods, that seems silly doesnt it?
  • 2 1
 @nickfranko: Prolly, I mean, who cares really?

I think I had a couple more semi-factual statement in my comment, but thats just like my opinion man, and maybe yours is different, and thats cool.
Not much reason to get to worked up about it
  • 1 0
 @onawalk: You were talking about 20 years ago, right? He was nowhere near a Santa Cruz back then, he still had to start with Honda! I was talking about the Orange bikes. Peaty was still on them, Minnaar was on Haro but had a good few years on Orange before that.
  • 1 0
 @vinay: Cool
Not sure I looked into it too deeply, just going off memory.
Appreciate your fact checking, but you get what I was hinting at yeah?

We are adaptable animals, and the bikes of 20 years ago, were/are still very much rideable, regardless of what some think
  • 2 0
 @onawalk: Yeah, the confusion was that Orange bikes had quite modern geometry (whereas Santa Cruz was indeed quite short and steep). But I do get your point, people could ride some pretty amazing stuff on them back then. People (luckily) can indeed adapt to a lot. Probably also the reason I'm not one for such a systematic approach as suggested when setting up the suspension. Like consistently ride the same section, change one thing at a time etc. When my suspension behaves differently (within limits), I use my arms and legs differently. I think it could work well for a rider who is really dead set on what the suspension should behave like. But I think I'm more dead set on how I want to ride my trail and just compensate for what the bike does to get where I want.

However for bigger changes in geometry and suspension it really does take a good bit to adapt. A few months ago I broke a more modern hardtail and for the time being started to ride my 2007 Cannondale Prophet again. It really took a good while to exit a corner more or less where I intended to!
  • 9 4
 After watching old Syndicate videos showing Minnaar and Peaty dusting the field on V10s with 26” wheels, 67 deg head tubes and frames more akin to a S or M today (with associated chain stay lengths) my only conclusion is…we absolutely need need size specific chain stays.
  • 7 1
 The question is would they dust the field on those bikes today, against all the other bikes of today. And I’m going to take a leap and say no.
  • 4 1
 @BiNARYBiKE: I omitted the “/s “ but amend my contribution based on your well thought out reasoning.
  • 10 1
 What if I can't manual? How do I choose a chainstay length?
  • 31 1
 Go for an automatic instead.
  • 2 1
 Get 2 chains: longest chainstays that will work with only 232 links.
  • 8 1
 Then you're free to go Full Aston and run a tandem with the stoker seat removed.
  • 1 2
 @bigtim: underrated
  • 1 0
 Keep making your chainstay shorter until your bike turns into a unicycle and you have to manual everywhere, problem solved
  • 4 0
 Solution:

Same size rear stays or swingarm or triangle depending on design with modular 3D printed dropouts with open source 3D Print designs and material requirements.

Don’t like your existing setup? Print another.

Brands can charge for the design files and lay-off the manufacturing to the consumer, reducing sales price and increasing post sale engagement.
  • 4 0
 I definitely noticed a difference going 6mm longer on my Spire. It felt it felt like I could ride more from the middle of the bike and not have to go for an after as much in corners maybe it was just the suspension and tire impact that you mentioned though interesting read
  • 1 2
 Sorry voice to text!
  • 7 2
 @Agleck7: comments are for keyboard warriors. This isn't a dictatorship
  • 5 1
 I’m on team “meaningfully size specific chainstays” personally. I’m also a taller rider (6’1” barefoot), which means personally I want long chainstays.

And like the article says, it’s all about proportion. Bikes with shorter front centers (steeper HTA’s and shorter travel) don’t need/want as long of a rear center.

I think people who value speed/racing tend to prefer longer stays than people who tend more in the “jibb and pop” style of riding. I mean, look at all the DH bikes with super long stays (Supreme, Legend , Supernaught, etc), then look at what bikes the Ride or Die crew or rampage riders are riding (sizing down for ease of throwing around, etc).

The other thing is what long chainstays allow for. My first bike had 425mm chainstays, and a low stack height (I assume to keep weight on the front). My new bike (Banshee Titan) has 452mm chainstays, and has a much higher stack height, because the longer stays put more weight on the front natively, allowing the stack to grow. And more stack helps in the steep stuff, and helps with the manual situation a bit.
  • 4 0
 I've got adjustable dropouts and can definitely confirm the huge difference in ease of manualling. The longer setting is a better balance to the front end and the bike generally rides better like that, but I missed being able to get the front wheel up with ease so much that am back to the short setting now.
  • 9 3
 Can we please stop with the over customization? Pros will always get that ability, but weekend warriors will notice the cost increase more than the benefits.
  • 4 0
 This fickle MTB consumer community needs 100% size specific EVERYTHING top to bottom. I want size specific tire tread thickness, compound, side knobs tailored to my exact lateral cornering ability specific to the geological attributes of my favorite trail. Got that?
  • 4 0
 Proportional head tube length is probably more important than proportional chainstays. I hate it when a tall guy needs loads of spacers or other fixes to keep from being hunched over on an XL frame, when a short-to-average person on a S or M frame has nearly the same headtube and a reasonable body position. Sometimes a shorter person on a bike with a long travel fork will be standing nearly upright in the pedals, without so much as a big riser bar.
  • 2 2
 Так, друже: 30мм проставок + 75мм кермо, бо виробник вирішив, що 110мм рульового стакану для L-достатньо.
  • 2 0
 @Beskyd: ми в згоді!
  • 6 0
 Wait, so I have to be able to manual to make a decision on this? I’m f*cked!

Doctor, will I be able to play violin after this operation….
  • 2 0
 Underrated comment.

Obviously my chain stays are far too long. ;-)
  • 3 0
 Seb, I enjoy how much thought you put into the nuances of bike fit and geometry. The very tall and very short rider is often overlooked by bike companies when they design their bikes. It’s nice that PB has at least one properly tall editor to get a perspective that isn’t 5’10”.

I think that geometry is in an interesting place. The industry seems to have a found the limits of longer/slacker and will be doing smaller refinements vs the major changes that happened in the last 6-7 years. Seeing bikes get proportionally longer rear centres with higher stack heights is a trend I want to see more of going forward. The new v10 has 455-460-465 adjustment in the XL via 3 position flip chip which I think should become a standard. Let the end user figure out what they want with options to change it themselves.
  • 3 0
 @seb-stott why not ask the Geömetrön boys to help you test this as G1 has 4 mutators to lengthen the chain stay. The mutators are 33mm, 41mm, 47mm and 54mm and grow the chain stay from 447mm to 468mm on a size large, also depending on the seat stay mutator. But that offers 21mm of adjustment to play with while otherwise keeping the bike the same
  • 3 0
 This one really makes me wonder how my weight distribution is. Shouldn't be too hard to figure out with one bathroom scale under one wheel and a tile under the other (to keep the bike horizontal). My current bike (hardtail) has a 415mm rear center and a 1214mm wheelbase. I feel it is perfect for cornering as it is now. My previous frame had a 420mm rear center but the front was a whole lot shorter so at least a good bit closer to that 50/50 balance. But I felt it was really hard to keep the rear wheel in check (without pedaling and/or braking obviously). There is some fun in oversteer but it also means you keep losing your speed, let alone that you can gain speed. I'm not going to argue with the theories here but it doesn't jive with my experience. Obviously riding bikes (and riding corners in particular) is a dynamic process and even though a constant radius and constant speed turn do allow themselves to be modeled as done in this article, it is not how we mountainbikers (like to) ride our corners. That said, I won't ever argue with Taj artwork so whatever comes with his giraffes and corgis I'll take for granted.
  • 3 0
 Seems like this debate could be mostly distilled down to solving this challenge:

Creating a properly balanced fit and weight bias for taller riders.

Which the rider will then decide if they want to... bias (slightly compromise) their particular setup towards either climbing or descending.

And it seems like - with rare exception - the only part of the available arsenal that gets thrown at this problem is more reach, and more chainstay length.

And occasionally seat tube angle. but that debate seems to have settled down into the 76° - 78° range, with plenty of available fore and aft adjustment for most anybody.

So this current debate seems to dictate that we create the supposedly ideal (theoretical) proper bike fit for a 6'-5" (195.58cm) rider, by only using more reach and chainstay length.

And by following these supposed ideals, you could quickly end up with 520+ reach and 450+ of chainstay length. Without my geometry calculator handy, and with today's slack head angles that's gotta be ~1300mm or more of wheelbase.

Now you've got a bike that handles like a 70's station wagon on anything that isn't plowing straight down the hill.

Yet, why is it blindly assumed that the best stem choice for EVERY rider is 40-50mm? And don't get me started on the 6'5" guy who thinks that the latest 35mm stem is a performance upgrade.

And for some reason it's also blindly accepted for many taller riders to automatically go with a stem in 0° (maybe 6°) rise, often with 2"-3" of spacers under the stem.

Does anyone ever consider how DORKY this looks?! Let alone how less-than-ideal this is.

Does anyone ever consider how much flex might be happening in this extra steerer tube length - especially with a 6'-5" 220lb guy torquing on a set of 800mm bars? And extra useless weight with steerer tube and spacers?

So the only direction we've been heading (we've been allowed to go) over the last handful of years since modern geometry has taken it's course, says that as the rider gets taller, his body mass can ONLY shift rearward, along with the upward that he has no control over - and this can only be addressed and compensated for with longer chainstay length.

Consider this: For taller riders, as the handlebar height (which is actually hand position we're talking about) gets taller, through stack height (headtube length), stem spacers, and handlebar rise, did you ever think about how far rearward your hands, arms, and body mass are being pushed, further amplifying the effects of what this article is about?

Did you ever think about the "normal" hand position that the average 5'-10" (178cm) guy or gal has on the average large bike, in vertical relation to the front axle?

Think about how much further rearward a 6'-5" guy's hand position is once you get your stack, stem spacers and handlebars up to the altitude you want them. Which, along with their mega seat height, has their center of mass WAY BACK over the rear wheel.

What if the real sweet spot for taller riders - along with modest (500-510mm?) reach, and maybe 10mm more chainstay length), might be in moving their body mass... not so far rearward, as dictated only by the seat tube angle and how high the seatpost is extended, but instead use a strategic amount of stem rise and reach, along with a similar amount of handlebar rise to get their hand position somewhat further forward. Thus allowing for easier control of weighting the front tire.

So here's what I'm proposing.

And trust me here... the world will not stop spinning on its axis if you go over the 50mm line on your stem length. Taller riders will have more than enough extra arm length to compensate for a bit more stem length. It's a non-issue.

**A case study of sorts**

I have two lifelong friends who are 6'-4" to 6'-5", 210-215lbs, who have always struggled with finding or creating a bike that fits them properly, feels right, climbs well, and inspires confidence.

Modern reach numbers have gone a long way to help their situation. But they were still struggling to find something that truly felt like THEIR bike.

So one of them asked for my help in creating the mythical/magical ideal bike for him, starting with a blank canvas (which doesn't mean a custom frame).

In watching them ride their current bikes - both of them being Horst Link arrangements - the first thing I noticed was how deep into their rear travel they would run / wallow. The "chopper" effect was always there, extremely so with their height and rearward weight (shift).

Don't get me wrong, BOTH of my bikes are Horst Link, and for certain riders and situations, they are awesome. 5'-10" 155lb me thinks so.

Always balanced and active, predictable and plush. But you know the downsides that come with the uphills, and the Band-Aids that we have to accept with Horst Link bikes, be it the blue lever, or on my Scott Ransom the REAR ONLY Twin-Loc (which is actually VERY effective in controlling the wallow and raising the bottom bracket for climbs).

But Horst Link bikes may not be the best choice for taller and heavier riders, because all of the leverage and weight shift that their height and weight generates... just doesn't work so well on such an active suspension design.

I'm getting off track. But my point here is, maybe first choosing choose a rear suspension design that works better with your height and weight is the best starting point.

For my friend, our starting point was the latest model Ibis Ripmo. An XL has a modest 500mm reach, and it's reputation as a magical do it all bike is earned and well deserved. What about the horrifically short 435mm chainstays?

But a major key in my friend's equation is that a DW link design (at least Ibis' particular one) doesn't sit very deeply into it's travel, or at least doesn't respond so radically to the extra height and weight (shift). And it pedals and climbs like a raped ape.

So fast forward... all of the relatively Gucci - yet robust enough to handle his size and weight - parts were carefully chosen, the bike was built.

Yet the two most carefully considered parts were the stem and handlebars.

The goal was the aforementioned strategic amount of stem rise and reach, along with a similar amount of handlebar rise to get his hand position somewhat further forward. While hopefully using zero stem spacers.

For the stem we chose (oh, the horror...) a 25° x 80mm Profile Design Aris, which is forged, safe, beautifully crafted and relatively lightweight (around 140g with titanium bolts installed). That got him part way to the hand height he needed.

For the other part, we chose a set of Specialized S-Works Carbon DH bars with 38mm rise, weighing a reasonably light 235g. We specifically chose 31.8mm.

You may be thinking that this combo would look gangly and awkward. The 80mm reach NUMBER on the stem may remind you of the early days of MTB, and the 80-100mm tillers that we used to run.

But, however they measure this 80mm appears to be NOT on the 0° plane, but along the 25° plane. They also have 60mm and 70mm, which look very normal ACTUAL reach, with some extra rise.

So it looks remarkably natural, and along with the bars - in using both of their rise, reach and sweep to get the grips up to where the hands want them - looks remarkably correct... and actually ELEGANT. You have to see it to believe it, especially watching a 6'4" to 6'5" guy ride by.

"Well yeah... how could it be any other way?" was my reaction

Fast forward... as we're doing some final fitting and fiddling before the maiden voyage. Only a few experiments were made with the fore and aft position of the saddle, simply 5mm each way to try it, and a bit of handlebar roll for personal taste.

The first test ride? It was an absolute revelation to my friend. Never before has he so instantly felt comfortable on a bike. Instantly felt properly centered (weight biased) between the wheels.

The next few rides - after fine tuning suspension, saddle tilt etc - produced similar WOW! moments. To him, no bike has ever felt so automatically comfortable, confident, flowy, and connected directly to his brain.

I've since done the same experiment with my other tall friend, this time starting with an XL Ibis Ripley V4. Same bars and stem, nearly identical components. The results were equally mind blowing for him.

So rather than knocking it, or dismissing this out of hand, maybe give it a try.

Are you less tall (6'-1" to 6'3"), or want to split the difference? Give a 17° FSA V Drive stem a try, in 60mm or 70mm reach.
  • 1 0
 Cool post. I too have gone longer with stems - 50mm (I’m 6’) and it’s been great.
  • 1 0
 Great write up, however you are completely disregarding the impact on steering when your weight is pushing in front of the wheel axle.
  • 2 0
 @ponyboy24: I'm actually fully attuned to the effects of this.

For the extra 10-15mm of actual effective stem reach that we're talking about, I'm suggesting that taller riders should be including this variable within their experiments to create the best possible front to rear weight bias, rather than giving it all to longer chainstays.

Also, at which point, and measured within which plane is this "in front of the axle" happening?

Have you considered that your handlebar sweep (creating your actual hand position) erases all of this?

Even on one of my bikes with a 60mm x 17° stem (equals zero spacers), my bar sweep brings my hands back slightly behind the wheel axle (figuring for the forward axle offset), and approximately equal to the steering axis.

You could have an absurd theoretical 150mm stem, and as long as the equally absurd handlebar sweep brings your hands back to their ideal position...

Bottom line, for taller riders, stem rise and reach should be one of the variables in play, rather than short or shorter stems being a religion that cannot be questioned
  • 3 0
 Taj art > AI generated, and most pictures too.
Banshee dropouts ( in the shop i used to run) solved so many problems , that certain customers asked how/ if / why we couldnt and if we could use them in all bikes…..
the idea is actually really good, so big time 2013 kudos to banshee ….

With so much of THE MOUNTAIN BIKE pretty sorted, the stand out development to sell ALL OF US ( the freaks and hard core, the nerds and absolute shreddiest of shredzzz) newer and greater bikes each hear is either gonna come down to ( you decide with your dollRs ) new electronic gadgets or supreme dialed maybe adjustable maybe not perfect geo for that certain buyer.

Given the choice of exact same dirt bikes i chose the more expensive orange one because the seat hight was taller and the fork was damped better for a bigger rider. If that means anything to a product mgr, the austrian moto product mgr won that day for both of us……

Bikes are so good right now!
  • 2 0
 One thing that's never really mentioned in these discussions: people don't sit upright while riding a bike. If the seat tube angles are the same, a taller rider's weigh bias is going to be further forward of the cranks than a shorter rider because their entire upper body is longer and further forward.
  • 1 0
 That depends on the seat angle. The taller the saddle height, the further back you sit. But cornering grip while seated is a moot point anyway.
  • 3 0
 I would like companies to offer options for chainstay length. I like as short as possible lots of others like longer. It would great if we could order chainstays like hangers and frame bearings.
  • 1 0
 Nicolai/Geötrön does this
  • 4 1
 I think all of us are in doubt now that the first major player went Paul Aston sized chainstays (Forbidden). At least for the short king that the XL was designed for. I will still have to custom order a properly sized bike.
  • 3 1
 You can't ignore the handlebars, otherwise you're doing the same thing you complained about the physics teacher doing. Yes, normal force proportional to friction force is idealized and not real world, but is working out all this with the idea of the rider putting all their weight solely above the BB. You could at least try to find an average location for CG, it will be in front of the BB, and compute the front-rear weight distribution from that. Or even get a couple scales and measure it on a few bikes with a few riders and get a general formula that takes into account the handlebars. Doing it with just the BB is pretty silly.

There is also the "window of movement" aspect. Weight distribution pushed too much to either end means you have less freedom to make adjustments before going outside the window of viable movements. That 25/75 distro not only means the rear is more likely to slip, but also that it would only take a small movement rearward to push it well beyond 25/75 and force a slide.

Or a loop out: you didn't talk about climbing at all...
  • 4 0
 Poor Paul here is struggling so much his 490mm long chainstays. *sarcasm* www.youtube.com/watch?v=COx76_HApRw&t=435s
  • 3 2
 He likes to steer boats, but doesn't appear to be particularly quick?
  • 2 0
 Man, if only Aston was as quick on a bike as he is to complain. Then you might have a point.
  • 1 0
 @TheRamma: For my style of riding, which is point and shoot and really hauling it, I believe his ideas will continue to inspire future designs.
  • 2 0
 @joni0001984: which is fine. There's no one "right" way to bike. Having read a lot of Paul Aston's stuff, I don't disagree with his preferences, I disagree with his certainty that his preference are universally correct or better.

He's also a ridiculous whiner.
  • 2 0
 @TheRamma: My first comment was to call him a bit of a Diva, and he didn't like that. But I had just watched 20 minutes of him ranting on Norco for him loosing a pivot bolt in the mountains. But it turned out he was right because (this is from my poor memory) 1. it was badly designed with only 2-3 threads. 2. Even with their solution (loctite) the bolt rotated and came loose. 3. They spent 6 months finding him a new bolt. 4. Boss wrote an appology letter to him, but missing a few points.
  • 1 0
 @TheRamma: To change things for the better you first have to identify the problem, and that usually starts with some whining.
  • 2 0
 @joni0001984: except when the whining is "why does it take so long for things to get shipped to me/to get good service?"

Dude moved into a dilapidated farm house in the Italian countryside for the cost of "a few ebikes." Of course shipping and support is going to kind of suck when ordering DTC. There is a downside to moving to places like that.

The mechanical issues he has (chains falling off, loose bolts) would frequently be handled by a good shop mechanic, yet he complains he doesn't have a crank pulling tool or a brake mount adapter as though that's the company's fault. Most of his problems would be sorted in a day at a decent shop. Yet it costs him "weeks" of time off the bike for every problem.

He takes no responsibility for his own role in these "sagas." Still doesn't mean his observations are bad, but he's supremely biased by believing his unique preferences are somehow universally "right." Dude gets high on the smell of his own farts.
  • 2 0
 @TheRamma: Ouch!

Yeah, Ebay had some warnings about even shippping things through the entire country of Italy. His new Nicolai frame arrived completely scratched up.
  • 2 0
 @TheRamma: I doubt the LBS can magically CNC a custom Norco Shore pivot bolt. Or braze a cracked Starling frame in the bottom bracket, that should have been welded in the first place. Or weld a Commencal Supreme with a very common cracked bottom bracket, without knowing the specific alloy and heat treatment.
  • 2 0
 @joni0001984: yeah, I still pay attention to him because he has some valuable insights. You just have to accept and account for the fact that he has a tendency to whine endlessly, and take what he says with a big grain of salt.
  • 2 0
 in other words, If you can weight your front tyre you can get away with shorter stays much easier.

I have several bikes and one has a 22mm longer chainstay than the rest(average lets say) - I can notice the extra on the rear instantly, the bike is much more lazy on slow trails etc - it also cant be ridden hard or aggressively or the back end just slides around - however this can also be good on some steeper corners as you lean forward and the rear snaps down and around.
i also find it harder to ride steep tracks as it feels like the rear is still back up the hill and its pushing me forward.
  • 5 0
 “Does this weight distribution doesn't matter? Unfortunately not.”

This passage from the article sums it up perfectly.
  • 1 0
 Girl, you phrased that so weird.
  • 3 0
 6’4” and the longer the chain stays the less the front wants to wash in corners. Going back to an older bike when my new longer chainstay bike was in the shop really revealed it - almost scary.
  • 1 0
 Funny, for me the shorter chain stays make it harder to control the rear end from oversteering. I think I adjust to getting front grip without thinking about it much, but the result is different behavior from the rear I have to adapt to when switching between bikes.
  • 2 0
 I love short chainstays because I grew up riding trials. I expect my bikes to pop onto the backwheel at the slightest shift of weight backwards. Unfortunately bigger wheels and longer stays mean I can't manual for shit anymore.
  • 2 0
 Fractions of a percent in the right or wrong direction matter-- We can all notice 2mm of seat height, 2mm of bar height, 1 degree of handlebar bend, 10mm handlebar width differences. Of course we can also notice a few mm of chainstay length.
  • 2 0
 @seb-stott

Legit. Seb is always giving proper content to read and learn how to improve your setup. With proper backing information to support his thoughts. Need to give credit where it due. Rest of PB staff please take note. Dont care about you not wanting to ride with other people or if you are late to ride.... Or commenting on what people do with their personal lives on youtube.
  • 4 2
 You can more easily compensate for short rear center by being more dynamic with your body position (getting your weight over the front wheel) but you can’t necessarily get farther back on a bike to try the reverse type compensation for longer rear center bikes. Not trying to say the problem isn’t amplified as you make a bike longer without increasing rear center. Just saying don’t take away my 435mm RC on Large bikes!
  • 3 0
 You refer to Forbidden, and state that there's no magical front-centre to rear-centre ratio, but I found it curious that the Druid V2 maintains a 1.78 or 1.79 ratio from S1 to S4, which is pretty much 16:9.
  • 2 0
 Always love Seb's articles. But the weight given to the flat corner weight distribution is too big IMO.
Thinking of BMX, chainstay length is a big part of the bmx handling. mostly for how the bike accelerate, pumps and gets airborn (think race bmx vs trail/street bmx). MTB is a mix of flat cornering, berms, jumps, rocks, .... Defining a golden rule based on grip or flat corners only/mainly is definitively not the way to define the single truth. It's the beauty of MTB geos, it's always a take on how you want the bike to handle and toward which riding style you push it.

An Idea for Seb, take two similar geo hardtails with only CS length that change (XC vs dirtjump), go on a pumptrack (tires on the ground, not even jumping), and see how the CS affect the pumping rythm, super intersting comparison and this difference will be found again when you pump and push in a MTB trail.
  • 1 0
 I'd like to see these free body diagrams redrawn with the bike on an angle and the giraffe in something representing the body position used when descending challenging terrain. I wonder if the merits of shorter chain stays could be considered as the breaking power biases to the front wheel as the trail gets steeper ...
  • 1 0
 Bought new this week, on its way (Marin RZ3). Last new bike was $99 CCM “MTB” from Canadian Tire in 1995. The forums on this site were very helpful. Also a rabbit hole of spec obsession. Don’t know my chain stay length, just looking forward to having brakes and stopping. I point my bike down hill, gravity controls my top speed and hope I stop without assistance from a tree.
  • 1 0
 I noticed all of this on our fullsus mtb tandem. The captain's weight is almost twice the weight of the stoker. Weight distribution wass around 51/49.This made the tandem react the opposite of my solo bikes. And indeed the front tyre needs a lot more pressure and a stiffer carcass not to burp(over 2.3 bar for a 2.4 tyre on a 30mm internal diameter rim. The rear tyre slides a lot more. The rear tyre has less rolling resistance than the front. The front fork needs way more pressure and damping, the rear shock less. The chain stays measure a bit more than 49 cm. The rear tyre never loses grip while climbing but does loose grip on the flat in the mud.I had to change the stem for one with 45° rise. and a lot longer to keep the same reach but get a better weight distribution. .An 80cm bar did not work, 74cm was fine.there's a lot more difference I notice but can't explain. The fact that a longer rear end gives more travel explains probably while over 3 cm of difference in travel between fork and shock works best.
  • 1 0
 Nice to have both options. Chainstay length selection would be a cool offering from companies. It was nice on the RM Instinct to be have chainstay adjustment. Definitely preferred it long for bikepark but chill xc short was way better.
  • 6 5
 Betteridge's Law of Headlines says...

Betteridge's law (of headlines) is an adage that states "Any headline that ends in a question mark can be answered by the word no." The sweeping generalization refers to the poor journalistic practice of writing sensational headlines in the form of a question to compensate for the author's lack of facts.

Next year Pinkbike starts its new "Top 10 Reasons Riders are doing this..." Buzzfeed format.
  • 2 1
 Is flat cornering really the best mental model here? On steeper terrain, long stays tend to reduce grip on climbs (at least until the wheelie point), and downhill often needs getting weight back.

Flat terrain, slack HA, sure longer stays probably help but what are you optimizing for?
  • 5 0
 Dang, no poll? Disappointed...
  • 1 0
 I think the rider's weight isn't important here. "Size specific" is specific to rider's height, or proportions. Not specific to body mass. Also geometry of bikes rear end is pretty important, too. I can bunny hop faster and higher on old Banshee Rune with 435mm chain stays than on Nukeproof Snap with ... 420m chainstay. Interesting, isn't it?
  • 3 0
 As a bigger rider, fore aft movements of ny body have a much bigger impact on my bike than those of my lighter buddies of equal height. Yes, more leverage (long limbs) makes it easier to manual, for example, but so does having more weight to throw around at equal leverage.
  • 4 1
 As a tall rider (6ft 5”) who prefers to have fun and get sideways rather than go fast, longer chainstays on larger size frames are one of my biggest pet peeves
  • 2 0
 We need not only size-specific frames but also weight-specific components. How can a bike designed for 60kg have the same fork, wheels, bars, and everything with the same stiffness that a bike designed for a 100kg rider?
  • 1 0
 6’4” 110kgs and I break absolutely everything. But it’s hard to ask the world to suit the ends of the bell curve. Ebikes have helped usher in a new crop of stronger components where the lightness imperative doesn’t compromise the ideal design as much, but I still break things.
  • 1 0
 I think for forks that already exists - but it would be good to give more flexibility for travel options on the smaller stuff (eg Pike/34s) - used to be able to go longer on them.

For other stuff, some components have 'weight limits' but guess the extra cost with batches makes it uneconomic.
  • 2 1
 Proper weight distribution has been completely overlooked for too long. The experimentation around head angles and wheel sizes over the past 20 years has largely been at the expense of optimizing the rider position *in* the bike. I have always sought out frames with optimal chainstay and wheelbase measurements to get me in the 45/55 ratio I prefer for XC and climbing.
  • 2 1
 Tall skinny guy here. I figured this out years ago. Appropriate chainstay length has more to do with weight than it does height. I'm now on a 435mm rear center with around 865mm front center. If I could make it a 430mm rear center, i would.
  • 1 0
 Came for a survey. YES!

A 420mm chainstay on an XS should not be on an XXL frame. Perhaps have 2 unique rear ends for XS-M and L-XXL frames, but put a flip chip in there? That way you can run something like 420-430 and 435-445?
  • 3 0
 What about weight balance when pointed downhill? Plus, the higher/taller the CG of the rider, the more weight that ends up on the front axle (load transfer). A vehicle with a high CG can combat the load transfer during acceleration events via longer wheelbase and wider tack. For a 2-wheeled vehicle, this is stretching is important for theoretical maximum braking performance.

Interesting to see smaller riders on XS-M frames looking more "in the bike" and larger L-XXL riders being "over the bike". Stack rarely grows proportionately with reach, which also needs to change.
  • 1 0
 Nice one Seb for pointing out that mu increases with vertical load on an MTB tyre which makes them respond in the opposite direction to a weight distribution change on a car! This is why weighting the bars gives you more front grip.
  • 1 0
 As others have stated, I've recently experienced some drawbacks to short stays: steep climbs. The bikes I have been riding for the past few years have 440 mm stays and I recently purchased a short travel trail bike with 430 mm stays. Yesterday, I did a steep technical climb that on the bikes with 440 mm stays I can clean most of the time, but on the shorter bike I nearly looped out or could keep the front end from wandering to stay on the line required to clean the technical sections. This is despite the fact that the short travel bike has a head tube angle that is 2-degrees steeper than the bike with the longer stays. Don't have issues with a wandering front end or looping out with the slacker longer bike.
  • 2 1
 My ebike has 470mm chainstays with a 479mm reach. (probably closer to 470 reach now that I put a longer fork and 29" front wheel on it). Aside from being hard to manual it is super stable and corners really well. I like the feeling of being centered in the bike.
  • 1 0
 I ride a size small, which usually falls at the other end of the spectrum where the chainstays quite a bit larger than the reach. I recently built a Druid V2 and have only put about 40 miles on it. The static chainstay measurement is about 12 to 15mm shorter than every other bike I've previously ridden and it's a very noticeable difference. Wheelies, manuals, hopping around and cornering feel very different on this bike. I'm sure the axle path plays into that, but it's a far more playful bike than I was lead to believe.
  • 3 2
 This splitting of angel cocks into even more size configurations is what is killing the bike industry - nobody will be able to afford a bike if manufacturers feel compelled to make a size for ever single possible scenario. Just pick something and live with it!!!!
  • 1 0
 I'm 6'7" and have struggled always with short rear ends and a flagpole seatpost that puts me way over the rear axle with the arc that seat tubes have to navigate rear suspension. Literally to the point of having maybe only 5% of my body weight over the front. I always thought being far from the bars felt good, until I got my XXL Starling Twist which has a nice steep seat tube. I'm not stretched out like superman to get to the bars, and I've got plenty of uphill angle I can achieve before the front end even starts to feel light.

Chainstays are still on the shorter end. ST angle needs to go hand in hand with CS length. If you're tall enough, you can quickly negate a longer CS by having a slack ST.
  • 1 0
 Seb wrote the same article in 2022. 6'5" rider here and I love the size specific stays. Bikes that truly take the differences of rider height in to account and work to achieve similar body position across a range of sizes are great. The point about manuals is a complete miss - I didn't really work to master manuals until I got correctly sized stays, prior to then they just kind of happened easy peasy with the slightest hip shift.
  • 1 0
 To throw another wrench into the calculations... If we assume the same stem length on the IBIS example, the front wheel will be 15mm further in front of the handlebars on the S5 compared to the S1 due to the difference in head tube length. Should stem lengths also be scaled with frame size?
  • 3 0
 I’m a simple man. I buy a bike…I ride a bike. Getting lost in the details ain’t the way I live. Just point the dang thing downhill and stop worrying.
  • 1 0
 So the take away, if anything, is: Size-specific chainstays (at least in the way they are currently done) matter way less than some people would have you believe and you shouldn't worry about it. If your bike has somewhat normal geometry, you're all good.
  • 1 0
 My only real complaint with the article was its technical and in-depth nature coupled with the complete lack of any hints as to whether or not it would confirm my preconceived notions and current frame choices. Made it difficult to decide whether or not to invest the requisite time to understand it.
  • 1 0
 All this is based on a static riding position, and hasn’t considered the basics in physics.

Three main things that are missing, which are critical pieces on information. First thing is the individual person who rides the bike. Depending on their body proportions, specifically leng length compared to torso length, arm length, etc., the weight on each tire will be different proportionately. Next is riding position. They came up with this as if we are all just sitting in the saddle. Different riders weight the bike in different ways. After a few rides on a certain bike, I naturally lean forward more on some bikes to weight the front wheel. Then we get into constant differing terrain. And we haven’t even gotten to how the individual sets sag.

Basically, there’s not much data here to come up with any real conclusions other than different people have different preferences based upon many different things.
  • 1 0
 @seb-stott it's really good stuff.

I have a question: considering we are alternating between hard and soft surfaces, do you think having a more even mass distribution can bring more predictability?

Since we will get instances where our wheel will get more or less traction than on a normal surface, a more uneven share of mass also brings a more dramatic change in traction?

I own a V1 large Forbidden Druid and the longer dynamic chainstay has been a revelation to me: I feel the bike is a lot more intuitive to ride than what I'm used to.

I've tried longer chainstay and other than on tight and steep stuff, I feel like I've not reach a to long chainstay.
  • 1 0
 Car analogies aren’t helpful. Completely different situation on a bike with a dynamic weight bias, the rider, and completely different goals for damping. I used to make theses comparisons too, but my track knowledge is useless for tuning my bike.

Nice article though, and a great discussion topic
  • 1 0
 One thing that is missed in the discussion about friction is that sometimes you aren't limited by the friction between the tire and the surface, rather limited by the yield strength of the surface. Some of the most fun conditions are when cornering in conditions where the dirt yields and you drift.
  • 1 0
 Of course there should be CS length ratios between sizes. Or maybe at least every two sizes. Currently the middle sizes have little difference and certainly less than between them and the extreme smallest and largest. For example between XS and S, or XL and XXL.
In my opinion, the size-dependent swingarm length more equalises the suspension characteristics between sizes. Especially for a tall person and a very short person it will make a difference. The greater stability of a longer bike for a tall person will also make no small difference. Remember what it was like to ride a short bike and a 26" wheel?
I'm thinking of people who are +180cm (I'm leaving out the geo).
In addition to this, brands for more conscious riders could have a mix option. If you can already order a bike for yourself and select parts, why not make different swingarm lengths available? I was talking about this the other day with a friend who designs bicycle frames. Although I'm not entirely convinced about it there is a point.
I'm riding Nukeproof Mega 290 size L and this bike have 450mm CS, reach 475 and i thing its great proportions for L and XL size.
  • 1 0
 Once again another desk jocky at ski mag .com outsmarted the entire bike industry and the science of center of gravity and fit.
I guess bikes should just come in one size and save everyone a bunch of money. If the rest of the bike doesn't matter, then it's only a matter of time till another silly article comes out about the front not making a difference.
"Planted" is trendy right now. That's great if you're racing or have no bike skills, or just like that set up.
CS is a key factor in how a bike manuals. It isn't the only factor but it's one measurement you can use at your desk to have a guess how the bike will ride.
  • 1 0
 Hmm.when going down hill the weight shifts forward, A LOT! So to have balance you would need shorter chain stays...right? And longer ones on flatter terrain.

All I know is that I am fairly tall at 188cm and love a 435ish CS. Tried 455 ones on a long bike and it was just dead.. fast but dead. So when racing blind it was harder to pick lines. I kinda just held on the the damn thing instead
  • 1 0
 For trail riding, I vastly prefer modest rearward weight bias over 50:50. I find myself more often getting my weight off the front wheel, than adding more to it. Over a long ride, that's a lot of energy saved not having to move from my pedaling/ready position. Based on putting scales under each wheel under my fav bikes in my quiver, I've confirmed that 60:40 (rear:front) is close to the sweet spot, but I preferred the bikes that measured to be 62:38 over the ones that measured 58:42 on the scales.

I've been buying high-end bikes since before 2010 and I usually always found upsizing made for faster bike, until the SB150 came around. The size M rode no worse than the size L. That's when I rediscovered the "CS length to WB sweet spot" in 29ers that I used to enjoy with short CS bikes and smaller wheeled bikes.

The reality is: most short travel bikes and smaller size bikes have too much forward weight bias for my tastes (in size S/M). Seeing Enduro geo on short travel bikes is a great sign to a shorty like me, since the WB is getting longer to balance out the already too long CS (which needs to be so for tire clearance). For tall folks, I can see the WB getting far too long if the CS don't grow with it. In fact, I've noticed a trend where shorter folk gravitated to slacker bikes with long forks and taller folk would brag about doing the same stuff on their short travel bikes that shorties did on big bikes.
  • 1 1
 I am missing leaning angle in this article. This is more important than the weight distribution when cornering. A long chainstays helps balancing but has not as much with cornering speeds. Precession is completely ignored here.
  • 5 0
 Love Taj's art
  • 4 0
 Wish I could corner as well as a giraffe
  • 4 0
 Don't care. I'm here for the Sam Hill picture,thank you.
  • 4 2
 Tall rider. I like short chainstays. If you make a bike with only long chainstays for my size, I'm likely not buying that bike. Give us options.
  • 2 1
 What do you consider "short"?
  • 2 0
 Just more frames with adjustable chain stay lengths. Versatility in frames is good. Just like adjustable geometry and travel.
  • 1 0
 Even if we didn't need size specific chainstays, having different length chainstays as a selectable option when making a bike would be an interesting idea. It wouldn't make any money, but it would be interesting.
  • 5 1
  Me halfway through this dissertation. I just want to ride.
  • 1 0
 This guy for president^
  • 5 1
 Levy knows what it means to be size specific
Mike Levy
  • 1 0
 I've always been curious to know what size manufacturers design the chainstay length around (as well as other geometry) I would guess medium or large but does anyone really know?
  • 1 0
 Not sure its that big a deal. I like the adjustable or options for different length drop outs. But what about the real need - different anti squat tuning for different frame sizes.
  • 1 0
 Longer cs and longer fc both increase anti squat (for a given cog) in a happy coincidence.
  • 2 0
 "I'd suggest picking the longest chainstay that still allows you to manual comfortably"
Anything over 420 feels pretty awful to manual tbo.
  • 1 0
 @seb-stott :: You may get a kick out of the ride impressions during the “long tail” Esker Hayduke review m.youtube.com/watch?v=zGJ1MVRXYTs&pp=ygUPaGFyZCB0YWlsIHBhcnR5
  • 1 0
 Let’s be honest, there are a lot of people on here who think that they would know the in length, but come on, just more people yapping about nothing!
  • 9 6
 Do we need size specific anything? Abolish sizing once and for all!
  • 3 0
 How is there no poll? Flip chip or sliding dropouts sound best to me.
  • 3 0
 And here I am riding my unheard of 473mm chainstays...
  • 4 0
 You on a tandem?
  • 1 0
 @plustiresaintdead: Hahaha, Banshee Legend
  • 2 0
 Yes. So much yes to longer chainstays on XLs. At least give us the adjustability option to keep everyone happy
  • 1 2
 The weight distribution approach (34.6% vs. 65.4%) is for people standing upright on their bottom bracket. I don't, I usually stand on my pedals, and hold my bars while riding. Thus my weight is pretty much shifted forwards. Actually, I don't know, how much. So the approach seems interesting, maybe a key to figuring out chainstay length?
  • 4 0
 What would Levy think?
  • 2 2
 Think Levy would argue in favor of short chainstays.
  • 1 0
 90 percent of the ski's have binding mounted behind the center, so no bikes do not need 50/50, however I agree that chain stay sizes should be in place
  • 4 1
 Don’t think this guy knows what he’s talking about
  • 1 0
 Welcome to Pinkbike! Please insert credit card for more content!
  • 2 1
 Hahah funny number aside, 420mm chainstays are unironically perfect. Shoutout my 2018 Jekyll frame, I'm never getting rid of this thing.
  • 4 1
 My Rootdown has 420 chainstays and I want all of my bikes to ride like that one does. More longer seems to me like more less funner.
  • 2 0
 Get a Nicolai G1 & problem solved with adjustable chain and seat stay mutators
  • 1 1
 I only ride the one size of any bike so aslong as that feels right I’m not bothered about the other sizes. I buy a bike based on the geo and personal preference of ride characteristics in the size that fits me
  • 1 0
 Ehhh. I wish they made head tube lengths bigger. Like my seat on my xl is way above my bars, put 35mm rise on, 50 would have been better but looks goofie as f.
  • 1 0
 "a tripping sensation on steep, technical sections"

I would appreciate if someone could rephrase or explain it to me, since I am not a native speaker.
  • 1 0
 I’m gonna need that giraffe riding the MTB as a sticker. Won’t take no as an answer.
  • 1 0
 Go to fairdale bikes. They are already there.
  • 1 0
 Pipedream is close to this with the Moxie.
Sizes:
Long
Longer

www.pipedreamcycles.com/shop/moxie
  • 1 0
 The rear wheel and tire width are limiting factors if you want a shorter chainstay.
  • 1 0
 Something worth adding to the article is the rearward weight bias of a mullet setup.
  • 1 0
 100%. I'd go so far as to say we need size specific wheels. L / XL 29er. S/M 27.5 XS 26
  • 1 0
 This! I've thought this for years!
  • 2 0
 Let’s Care more about the skills jsjsjs
  • 1 0
 I spend all week at work and then Pinkbike hits me with this! If the chainstay holds the wheel on it'll do.
  • 1 1
 Hmmm. Size specific chain stays make me think about the other end of the bike.

I wonder if the same applies to stems? Does anybody make a stems longer than 35mm?
  • 1 0
 If you want to make it even more complicated, compare same wheels vs mullet configuration.
  • 1 0
 But if you run a Fox 38 on the front, the bike will be perfectly balanced whatever chainstay length you have!!
  • 1 0
 Anyone agreeing that cs doesn't matter for manuals prob owns "manual trainer" and a Riprow. And can't manual.
  • 2 2
 Y'all need Paul Aston back or in your life. Made me see the light that it needs to be size-specific.
  • 2 0
 I pick 490mm.
  • 2 1
 Why not 489mm or 491mm?
  • 1 0
 @tacklingdummy: My current Banshee Paradox XL 2019 has 425mm, and that seems too short to me at high speed, and when climbing, the front wheel jumps up.
The best bike I have owned is the Mondraker Summum Pro Team L 2013 with 445mm chainstays. It felt good because it was stable at high speed, even if the cockpit was very cramped and seat angle terrible. For being a 26er it was a long and stable bike. Someone did a speed record on this bike down a mountain.
Now I prefer 29er or Mullet and the bike needs to be even larger.
  • 1 0
 @joni0001984: I was just joking, but I do agree with your comment on chainstay length and riding characteristics.
  • 1 0
 In italy we call it "seghe mentali"
  • 1 0
 Average height in Sweden is 181cm and in Italy 175cm. Meaning most Italians should not have a problem with short chainstays, but more Swedes would.
  • 1 0
 Easy; 2 or 3 rear ends with flip chips to cover up to 6 different sizes.
  • 3 1
 #askpaul
  • 1 0
 I Scrolled down for the none existent poll.
  • 1 1
 Classics Seb article. Nice one mate
  • 2 1
 Yes, short as possible
  • 12 15
 Anyone else tired of this guy writing 1000 word essays and being completely wrong everytime? What is your background again, doesn't seem like it's engineering...
  • 1 0
 Yeah. This pile of words from ski mag .com just proves nothing matters . I guess we could just make one size bike period.
  • 1 0
 I'm highly skeptical of the math the author used: "a chainstay length of 435 mm and the wheelbase is 1,256 mm (pretty typical numbers for a size medium these days). So, the chainstay is 34.6% of the wheelbase, which means 34.6% of your weight will sit on the front wheel and 65.4% will sit on the rear wheel.* In size 5 (effectively XL), the wheelbase is 1,328 mm but the chainstay remains at 435 mm, so the weight distribution becomes 32.8% on the front."

When I actually measured weight on each axle, using scales under each wheel in a standing pedaling position, I couldn't find a single formula that could match my results. I did find a general pattern though, regarding the sweet spot bikes in my quiver... with a little bit of rounding, I found that my favorite bikes had WB/CS lengths of: 1230|435, 1250|440, 1210|430, 1190|425... it's easy to extrapolate the pattern, and predict which bikes would be in the ballpark. Doesn't make sense to me, but every chance I've had to test it has not yet left me disappointed.

Learning from this, I also feel that wheelbase dictated a bike's quiver-worthiness more than its suspension travel. I feel that I'd be happy rocking a 150mm FS with 1223 WB (Yeti SB150), 160mm FS with 1306 WB (Geometron G1), and another 140 FS with 1152 WB (Canfield Riot) np.
  • 1 1
 yes
\
  • 4 6
 If the chainstays are longer than 435, it's not worth riding
  • 1 4
 Thank you for writing this down. But I don't care.
  • 1 4
 just came to say, Miata gang!
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