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1. Shandy - Member

   What difference does chainstay length make to the handling of a bike, and in particular a full sus bike?

   I've noticed a lot of manufacturers seem to produce frames with the same chainstay measurements across all the different sizes, because they can then use a single swingarm across the range.

   A lot of DH bikes come with adjustable dropouts to alter their chainstay, and a lot of people seem to consider chainstay length when looking at hardtails.

   So how much of a difference does chainstay length make? Surely putting all the size increase into the effective top tube will compromise the design of the bike and leave taller riders (like me) with what is effectively a different bike?

   Posted 3 years ago #
2. geetee1972 - Member

   This is not a definitive answer by any means, but here are some thoughts.

   Increasing the chainstay length has two principle effects. First it lengthens the wheel base, thereby making the bike more stable at speed at the general expense of agility. Second, it alters the weight distribution between the front and back of the bike.

   Downhill frames tend to have adjustable chainstays as a means of adjusting the wheelbase so that the balance between agility and stability can be tweaked to suit a particular course or rider preference.

   Your comment about not changing the stays and therefore changing the dynamic of the bike is spot on. Lately, a lot of frame reviews, in Dirt at least, which focuses mostly on DH frames, have been acknowledging this fact and the reviews are based very much on the frame size tested. A good example of this was when they tested Steve Peat's V10 a few years ago, acknowledging how different it felt as a large compared to the mediums they had previously tested.

   Some DH bikes have super short chainstays coupled with still long wheel bases, the Spesh Demo 8 is a good example, in order to increase the agility of the bike in corners without compromising the stability of the bike at speed. With the rear wheel tucked up underneath you, it is possible to steer the bike with the back wheel using a lot of 'body English', i.e. using your hips to snap the bike around a corner. The compromise with this design is that more of your weight is on the back wheel when in theory, the best place to have your weight is evenly balanced between front and back, with the option to move your weight forward over the front wheel in order to get more grip for steering. A lot of people ride over the back of a bike for fear of going over the bars, especially on steep terain, but it's not ideal because you can compromise how much control you actually have.

   I've read a few times now that bike design/sizing will always be compromised until people start making frames with chainstays that are different lengths rather than simply adding in space to the top tube. How true that is is anyone's guess, but pretty much all of the Elite DH racers are on bikes that have been customised around their size. So while it may not be economically viable to do this, the evidence suggests that it does bring added performance.

   Of course, there are manufacturers that will build you a tailored bike, for example Nicolai.

   Posted 3 years ago #
3. ahwiles - Member

   a 'classic' hardtail chainstay might be 16.5" = 420mm.

   My old Dh bike had 470mm chainstays. This meant i had more weight over the front wheel. the damn thing was nearly impossible to wheelie and was very hard to work off drops without nose-diving.

   However, it did give me bucket-loads of front wheel grip, which is always welcome.
   and i found i could skid-steer the bike nicely around alpine switchbacks, because the back wheel was a touch lighter over the ground.

   my new Dh bike has 450mm chainstays, and it's about right, i can manual it over drops, and i don't notice any loss of front wheel grip.

   my old speccy enduro has 420mm chainstays, it won't go round flat corners because the front wheel is so light over the ground. And it's a bugger to climb with - i have a lot of weight over the back wheel, if i try pedalling hard uphill i just wheelie-off the back.

   i'd say the difference between 420mm and 470mm is huge, but you are right, it's the balance between front/back wheels that is more important.

   Geetee mentions the Speccy Demo - which boasts super-short chainstays as a selling point (420mm - hard to do on an 8" travel bike). The rumour mill suggests that there will be a new speccy downhill bike sometime in the future, even if it's only a modified Demo.

   ~i'd be very surprised if this 'new' bike didn't have c'stays closer to 450mm.

   Posted 3 years ago #
4. cynic-al - Member

   Weight over the front wheel surely has more to do with where your weight is in relation to the front tyre?

   FWIW my view is that longer chainstays wil give more stability and less agility, but most noticeably allow more control/less wheelying on steep climbs

   Posted 3 years ago #
5. mountaincarrot - Member

   I ride a Thorn frame with only 415mm stays (centre to centre). I have no problems riding straight up anything, need move foward sometimes, but that's fairly normal practice.

   Posted 3 years ago #
6. ahwiles - Member

   Al - i weigh 80kg, that weight is supported by the back wheel and the front wheel.

   a longer c'stay will mean less weight is supported by the back wheel, but i still weigh 80kg, so more weight is carried by the front wheel.

   you're right, a longer c'stay won't put me any closer to the front wheel, but i'll be further away from the back wheel, and it's the ratio of those distances that's decides the weight distribution.

   yes, leaning forward helps on climbs, but geometry also helps/hinders. i ride large frames with long seatposts, so for a good climbing bike i look for long stays mixed with a steep seat-tube.

   i've retired the enduro, and now have a bike with a proper seat-tube, it's amazing how much easier climbing is.

   anyway, the original question was aimed at Dh bikes, for which my condensed tuppence, based on my observations, is:

   longer c'stays (440 or more): harder to manual, more front wheel grip.
   shorter c'stays (less than 440): easier to manual, less front wheel grip.

   (yes, you can move your weight around to compensate, lean forward, lean back, etc. but you'll have to move less on a bike with complimentary geometry)

   more or less, give or take, all other things being equal, etc.

   Posted 3 years ago #
7. clubber - Member

   mountaincarrot - Member
   I ride a Thorn frame with only 415mm stays (centre to centre). I have no problems riding straight up anything, need move foward sometimes, but that's fairly normal practice.
   

   Conversely, being 6'5" all my bikes have comparatively short chainstays (since they're the same length as the smaller frame sizes) except for one whihc has long chainstays and is noticeably easier to get up steep climbs without wheelieing.

   Posted 3 years ago #
8. Shandy - Member

   I am having a few issues getting used to my SX Trail. Its got 424mm chainstays and a horizontal top tube length of 606mm. I am very long in the legs, short in the back, and I'm having a lot of trouble finding the balance between under and oversteer.

   I've been off the big bike for 6 months and come back to a new bike. I still haven't felt the flow on the new one so I have been trying to decide whether I've lost it, or I never had it, or there was some kind of technical explanation. I'd say a combo of all three is to blame.

   Posted 3 years ago #
9. cynic-al - Member

   ahwiles - I know what you mean but c'stay length has a much more dramatic effect on the weigh on the rear wheel than the back. If you wanted to change the weight on teh fron you'd shorten the top tube. Manualling is dependant on more than c'stay lenght alone also.

   mountaincarrot - thing is you can't look at chainstay length in isolation - the Thorn probably has a steep seat angle.

   Posted 3 years ago #
10. geetee1972 - Member

    What year SX Trail is it? I have one from 2005 with more or less those numbers but I am totally the reverse, long in torso short in leg.

    It will take a while to get your mojo back but give it time as it will come back. Pretty much you can adapt to almost any bike in time.

    Posted 3 years ago #
11. Shandy - Member

    Its an 08. It feels alright, just different I suppose. I probably just need a few consecutive days on it now I'm injury free. I got a great deal on the frame so if we don't make friends I can always ship it on.

    Posted 3 years ago #

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