calstar 

Chainstays. Look at any bike specs(large manufacturers), no matter what the frame size the chainstays are the same length. The bigger the frame the longer the st, even with the same seat angle this is putting more rider weight back towards the real axle; this has to effect the handling of the bike(lighter front end). So....does that matter? I think it does. Same with fc, larger frames lengthen the fc, but zero cs lengthening. This is obviously an effort to save $ in manufacturing, I get that, but it seems like the larger bike would benefit from a little length.

Thats it, just rambling along here, hope you all are having a great holiday,

Brian

Andrew R Stewart 

But can a larger rider handle the ego hit of riding a bike with longer then someone else's chain stays


Really you're right in pointing out the lackings in factory bikes. Some of the same can be said for fork rake often being the same for the full size range of a bike, yet the head angle changes across that size range. Andy.

dsaul

Agreed. I think the relationship between the saddle and the rear axle has a noticeable effect on handling. On frames for larger riders, I always design them with longer chainstays.

Trakhak

Interesting topic. I recently made the mistake of buying a new bike with what used to be called sport touring geometry, with slacker frame angles and longer chainstays than I'm used to, and I don't care much for the ride. It's okay, but I prefer my shorter-wheelbase/shorter-chainstay bikes.

Lesson learned. From now on, for any bike that I consider buying, I'll use the wheelbase measurement as a pass/fail criterion. As long as that dimension is well under a meter (my favorite bike has a wheelbase of about 97.5 cm), I'll probably like the bike. I don't worry about the chainstay length, as long as the wheelbase is what I like it to be.

In the days when Tim Issac was designing Trek's bikes, someone at the factory (Tim himself, maybe?) told me that their touring bikes all used the same head tube angle and fork rake (for a given frame size); they'd just use shorter chainstays for the sport touring bikes and longer chainstays for the grand touring bikes. I believe that the chainstay length remained constant over the range of frame sizes for a given bike model, though, which would seem to argue against the idea that chainstay length should vary with frame size.

Edit:

The OP said that the use of the same chainstay length over a range of frame sizes is done to save money. But if the single most important dimension determining how the bike handles is the wheelbase, which is at least arguably the case, then it might be that the chainstay should remain the same length over a range of frame sizes to achieve the target handling characteristics.

After all, any bike designed for road racing, including elbow-to-elbow peloton racing and sprinting, would have a wheelbase under a meter in length. Chainstay length choices would always be severely constrained, regardless of the frame size.

unterhausen

at 73 degrees, you would need 40mm longer chain stays on a 65cm frame than a 50 cm frame to maintain the same distance between the center of the saddle . Not sure that makes sense to anyone. Is there really a demonstrated problem that is being solved with longer chain stays? Or is it merely a hypothetical problem? Most performance bikes are simply designed to have the shortest chain stays possible, I don't think it's a case of one size fits all. The thing that bothers me about production bikes is the short front center on large bikes, but maybe that's one way to address this issue with the chain stays.

fietsbob

Predominantly, Folding bikes are an entire product made in one size..

calstar 

Is there really a demonstrated problem that is being solved with longer chain stays? Or is it merely a hypothetical problem?

I don't know if there is a demonstrated problem, just seems like the center of the riders weight being balanced(relatively speaking) as well as possible between axles is a good thing. Maybe its the "its always been done that way" mindset.

Most performance bikes are simply designed to have the shortest chain stays possible, I don't think it's a case of one size fits all

How about non-performance, non-race bikes? I believe at least one reason for the move to as short as possible chain stays(in the mid 70s?) was the lack of stiffness of chainstay material, as riders got stronger shorter stays made for a stiffer frame, with modern mtls this isn't so critical(again non-racer).

Oh yeah, I'm a really tall guy just looking for some knowledge/education here on the subject, not saying my opinion is the right one My bikes(2) do have long stays, have been riding bikes designed like this since i built my first frame in 1975 so I don't know what a short(er) cs bike rides like.

thanks for the posts guys,

Brian

twodownzero

Maybe the bikes with the movable rear dropouts are onto something? It seems that you want different sizes for different frames, but why not infinite adjustability (within a range) for the same frame size?

unterhausen

but movable dropouts will pretty much go one chain link, so they can be used with fixed/single speed. You aren't going to feel that. My previous post isn't really defending short stays, the mountain bike guys seem to like them, but I don't really see why it's all that important for a road bike. And I'm not super convinced for mountain bikes. But I haven't ridden enough different stay lengths to consider myself competent to say that.

I would say that people are open to using longer stays now. Jan Heine has said that it doesn't matter, for example

fietsbob

2 bikes, here, with adjustable but vertical dropouts, both are IGH equipped.. so its about chain tension setting on those..