Rumination on bike geometry
 

I am now in a place where 95% of my riding is off road, hilly and rural. I no longer go fast although I am getting into better shape. Got a Rivendell Clem Smith a few years ago and a modern REI hardtail last year. The Clem Smith was a bit of a revelation about very long chainstay geometry providing ride comfort in unpaved settings for easy speeds. So as I’m looking around it looks like Rivendell and Jones Bikes are the only folks making very long 20”+ chainstay bikes. Sure suspension enables one to fly down bumps but I really don’t feel like risking unintentional dismounts at speed these days. Touring bikes are around 17.5” chainstays which is not much longer than road racing bikes of the 60’s. And nearly all the hardtail or gravel bikes that take 2.6” tires are stuck in that 17” territory.
The long unsuspended bikes seem to be closer to the geometry of the bikes I see in pictures from the early 1900’s accounting for differences in modern fatter tire sizes. I guess I’ve become an outlier.

I've not direct comments on your ideas, though note you might get some useful responses from the folks over on the framebuilders forum.

20" is a darn long chainstay. With my usual 46-48 tooth crank, I'd have to splice parts of two standard chains together for one that long, although it's no worry with my 17'? 17.5"? stay. Have you found a source for longer chains?

There's probably a reason nobody makes bikes with really long chain stays.

Long chainstay's rule!

My Rodriguez everything bike has 20 inch stays. I can definitely confirm the bikes mellow character. So much is made of steering rake & trail numbers and their effect on handling. What few people understand is the righting action of the tiller effect of the ground going by acting on the rear wheel.

I don't know the exact engineering term used to define the distance from the steering axis to the contact patch of the rear wheel but the effect is real. Longer bikes do indeed ride more stable, have milder manners for a given trail number.

Maybe we're both outliers.
https://live.staticflickr.com/65535/...115a7363_o.jpgThe end of Garcia road by Richard Mozzarella, on Flickr

If shorter were always better, as many armchair bike designers seem to claim, we'd all be on unicycles! :thumb:

My hunch? Someone will make a well thought out bike for off road with very long chainstays and this will take off as a niche of gravel cycling or maybe a bigger trend. But this won't happen until two criteria are met. 1) The bike. (Obviously) and 2) The stars. (The right promoter, the right time and place ...)

Why do I think this? Well, 130 years ago, bicycles not all that different than what we ride today were dialed in by the brightest minds on the planet for everyday use on what we now call "gravel". Look at the wheelbases and chainstays they used. You could drive a truck through the gap between the rear wheel (which was often larger than what we ride today) and the laid back seat tube.

Bicycles drove the move to pavement. As roads got better, bike geometry tightened up. Now that riding off pavement is returning to popularity, some bright mind is going to rediscover what was known back then. (I read that someone did research back then on optimum wheel diameter for different surfaces. Conclusion - the rougher the surface, the bigger the optimum wheel was. 27"/77c was just about perfect for very good surfaces (ie paved) but larger was better over the rough stuff. And funny, just a few years ago, it was "discovered" that bigger than 27" worked really well in many mountain biking situations. 29ers! If that researcher were alive today he could have said "told you so".

Restricting chainstays to available chain length? Yeah. Just like we all ride bikes with equal number of spokes front and rear. Good for simple minds and stockholders. (The English used 32 spoke front wheels and 40 spoke rears forever until those minds and $$s took over. Now ever coop has front wheels galore and shortages of rears. Mechanics spend their time rebuilding and replacing rear wheels.

In the late 1970s, as reported in "The Custom Bicycle," Cino Cinelli speculated that the increasing proportion of well-paved roads versus dirt/gravel/cobbles meant that racing bikes should gradually migrate to the use of 26" wheels (not sure what he meant by that, but clearly smaller than 700c).

To that end, he said that he had already had some custom 26" tubular tires and rims manufactured to enable him to experiment with building such bikes.

By the way, 29" (700c/622 mm) mountain bike wheels and tires are smaller than 27", not larger. Unless by 27" you meant 27.5" (650b/584 mm), not the traditional 27" (630 mm) wheel size.

I'm uncertain whether there's any primary driving factor, but I suspect that racing cycling along with the rise of mountain biking has seen to it that much of cycling's geometry remains "compact."

I, too, am fond of the more-relaxed geometries, a la the Rivendell Clem Smith type bikes. Love the ride quality. But then, I've never needed to cope with rougher cross-country mountain biking, never had an interest in outright speed or climbing performance, etc. I don't much like "twitchy" character in a bike. And while I suspect many people out there also would prefer the longer type frames, basically the whole of the industry has gone the other way in the past ~40yrs.

Yes, but - 26" only because that was what Joe Breezer, Gary Fisher and the other Mt Tam crazies could scrounge up and modify for those crazy runs down the mountain. Had zero to do with theory, engineering, sample testing etc. Suitable kid's bikes came in 26 inch. So did the tires and rims. So unsuited for much of the use that suspension was developed to make those small wheels ridable.

Yes. However, I was responding to the following (incorrect) statement.

. . . And funny, just a few years ago, it was "discovered" that bigger than 27" worked really well in many mountain biking situations. 29ers! . . .

Hence my pointing out that (traditional) 27" wheels are bigger than 29er wheels, not smaller.

Here you go.
https://cimg7.ibsrv.net/gimg/bikefor...30c2237056.jpg

Steve Bauer's bike. He didn't use it for long, though.

Modern MTBs achieve a long wheelbase and stability from slacker head angles rather than super-long chainstays. The latter are not popular because they make it harder to pop the front wheel up.

I know. I just thought we should see what 20" chainstays look like before we get to deep into this.

There are plenty of sensibly proportioned touring, gravel, and fitness bikes out there. They're designed that way for a reason.

Not necessarily for popping a wheel up but for general maneuverability and responsiveness. Understand that they're also running 2.5-3.0" tires and full suspension to keep the rubber side down, and the slack head angles are for downhill stability. Mountain bikes also use super steep seat tube angles to shift the rider's weight forward in order to keep the front wheel planted when climbing, and high bottom brackets to keep the pedals and chainrings from hitting rocks. There's very little MTB geometry design that translates to effective road riding.

You may me look! :)
1988 Schwinn Project KOM-10 (26x1.95 tires): 17.25" chainstays, 71 head tube / 74 seat tube angles
Works for me, no suspension needed or wanted, for my kind of riding, on roads and tame multitrack trails -- no serious technical stuff

With my Scott Scale hardtail bike I added a PNW dropper seat post and I like being able to lower the seat on the downhill trail sections. Lowering my center of gravity is a very effective way to gain stability.

I take lengths out of another chain. It is damn long but it really makes sense for my use. A Surly LHT w 18” chainstays was my first long chainstay bike and in 26” wheels feels plenty responsive. I got a Felt Cafe bike to leave at my daughters house which had slightly longer stays and it too felt responsive enough. I stopped using drop bars ten yrs ago and ride with bars about 1/2” lower than seat height.

Can you offer one? I raced bikes in my 20’s and had a bike shop until 1986. Had a Schwinn Paramount track bike from the 60’s that had 17” chainstays.
My $.02 is that very long chainstay bike is the antithesis of consumer products that appeal to the image of sport recreation which pretty much dominates US bike industry. A long wheelbase, long chainstay bike is a perfectly fine way to design a comfortable handling off road bike for moderate speeds without going to suspension.

When I had my shop mtn bikes were just coming in. I was totally in the road segment and started riding mtn bikes with the cool kids but at my light weight at the time thought Cannondales touring bike w its 18” chainstays made a great off road bike w 35 mm tires. As did a Specialized Sequoia w 35mm tires. I finally succumbed to fashion and got a front shock w 80mm suspension for a mtn bike and was blown away. Now I have a modern hardtail w 140 mm front suspension and even though it is excellent for desending it’s still more responsive than I need for easy speeds.

20” chainstays on a one off experiment.

There are be builders out there who can tailor a specialty frame to meet one's specialty desires.

the front center matters just as much (or more) if you want a more stable handling bike. In this measurement, a centimeter is as significant as an inch of chainstay. Tandem riders will verify, we know looong wheelbase characteristics, but that front-center is the primary determinant of steering response.

I designed my touring frame with 47cm(18".5") chain stays to gain clearance when toting extra large panniers. Ride quality when compared to my other touring bike with 45cm chain stays is noticeable. The thing does ride over bumps with a little less harshness. I imagine 20" chain stays would be heavenly, albeit a bit long for sustained out of saddle climbing with a load.

I like long chain stays, but short ones have their place out there.

You're not that much of an outlier, and millions of boomers are becoming more like you! So far, we're WAY under-served in the cycling marketplace. With all the models that Trek, Specialized, Giant, and other manufacturers produce, there really is no excuse for the lack of suitable alternatives for older riders.

My brother's Clem Smith Jr. has a 53" wheelbase. I used 18 links from a second chain, iirc. It's such a cushy ride that it gets downright boingy sometimes. It also weighs 32 lbs. Where are the 45" wheelbase step-throughs, or quality DF frames with longer geometry? How about a 22 lb. step-through model? How about a 17 lb. step-through model? I want a step-through that is under UCI regs!

Some BF wags will probably respond that there is no demand for such, but that is confusion of cause and effect, I believe.

I don't know if I qualify as a "wag" but it seems to me that a 20 inch chainstay bike is a niche within a niche.

Are there really "millions" of riders who want such a thing? Is the chainstay length something that is making riders unhappy with their bikes? I have been a member of a road club for 34 years and when people get into their late 70s and even 80s they have been getting e-bikes. Some even younger, depending.

And 32 pounds? You can get a full suspension XC style bike that is 8 or 9 pounds lighter with knobbies. I have an enduro bike that weighs 32 pounds.

There are lots of riders in their 70s who ride racing style road bikes. Some of them are fast and do long distances.

Yes, I know there are plenty of older riders who are more casual about it. I'm 69 and I enjoy a casual ride sometimes.