chainstay length

[Climb01742]

i think it was douglas who mentioned a few days ago the connection between chainstay length and how a frame rides. i've been doing some research since then on the subject. and i've been measuring some of my frames. my frames are all in the 55 cm size neighborhood. i have chainstays that range from 40.5 to 41.0 to 41.5 cm. and while i know that you can't isolate one aspect of a frame, my frames do confirm that the shorter the chainstay, the "quicker" the acceleration, and the longer the stay, the more stable the ride. would someone mind sharing a more in-depth discussion of chainstay length and its impact on ride? and on a 55 cm frame, how short could one go? 40? 39.5? how would it ride? are there limits suggested by shimano/campy for how short the FD/RD distance can be? thanks in advance for the education.

[zap]

Your observation is generally correct. I say generally only because frame material as well as tube dimensions/carbon lay up have an effect as well. Serotta's typically have longer chain stays and wheelbase for a given size resulting in stable handling. Serotta improved the accelaration characteristics by bending the chainstays. I think Ben was the first to come up with this design.

My wife has a 650 Serotta with 39.3 cm chain stay and Campy 9s shifts just fine. I wouldn't go any shorter since the angle of the chain will increase quite a bit as it leaves the chainring/arriving at the cogs when the chain is on either end of the cogset. This increases chain wear and reduces efficiency due to higher drivetrain friction.

In the 80's, an Italian frame builder (Riga?) had a road frame with split seat tubes. As a result of this split design, the rear wheel could be moved close to the bb with a very short chainstay length of 36 (est.) cm. Amazing acceleration but apparently the ride and handling were unique. You could get away with that short stay at the time since they were running 6 speed and wider chains.

[dbrk]

The claim that bending the chainstays led to better acceleration is pure, unadulterated nonsense. There is not one shard of actual evidence to that effect. Of course, that s-bend chainstays look cool and may compensate for some clearance issues is all well and good. I mean, I love'em. I think they are aesthetically a nice touch, especially on ti bikes when they are big muthas'. But this notion that they have one thing to do with "performance" is just rhetoric, marketing, and unsubstantiated by any scientific measure. Ask any great builder except those who sell them...

No offense meant here. Just a comment about words and realities.

dbrk

[zap]

None taken.

Just stating what Ben has been saying for years. In my post I should have mentioned that.

I wonder how many builders actually have their designs and claims independently tested. Probably not many. And does it matter! Just ride what works for your application and make sure it fits.

[93legendti]

I would think, from a physics standpoint, that the s bend allows the chainstays at the points closer to the bottom bracket (before the stays flare out) to be closer together. This allows a smaller" triangle and, thus, the stiffness would be increased thereby insuring more efficiency. I know My legend ti with s bend stays accelerates faster than my trek 5200 and 5900--even though the treks are almost a pound lighter...just a thought.

[shazer]

I think this discussion is a good one, but I'm having trouble with the comparisons here. Too many subjective areas and too many variables. My 64 cm frame will not perform the same as a 54 cm frame and my experience with chainstay length is directly related to frame size.

My previous steel custom frames all had 40.5 to 41 cm chainstays, but with a 64 cm seat tube, a steep angle was required for rear tire clearance and previous builders were reluctant to increase wheelbase over 100cm. My top tube length ranged from 57 to 62 cm! These bikes were quick and responsive, but extremely rough riding and literally tiring to ride for long distances. Crit riding was great, but those races are generally shorter with a little better road surface on the average.

As I remember, Greg LeMond started relaxing his seat tube angle and others started to follow to where we're at today. If you look at old posters of his position, there are very few of us "mortals" that could hold that position for very long, let alone race the whole season, but it worked for him.

My Serotta has 42 cm chainstays and a wheelbase nearing 102 cm with a seat tube angle of 71.5 degrees. This bike is fast, responsive, stable, with no movement in the bottom bracket. I can ride for hours now and not feel beat up. I love this ride now, but my body is older too. I've wondered a lot lately what my performances racing would have been had I ridden this geometry twenty years ago!

Does chainstay length or bend affect the overall ride? I'm sure it does, but can I determine this while pounding the pedals? I doubt it is all related to chainstays. You have to look at the whole of the frame geometry to affect ride. I know that I got a lot of comments when I posted my bike in the gallery a couple of months ago, but for my body, the geometry works and I'm riding more miles now than I was ten years ago, and that has to be a good thing.

shazer