Re: Why Are Modern Stems So Short?

Donald Gillies said:

I am not an expert in these matters, however, I believe that if you
body is in the same position on the bike relative to the wheels, it
shouldn't make much difference concerning chainstay length.

However, once the rear wheel comes "out from under" you and starts
"being towed", you are placing much more weight on the front fork, and
this may mean things like (a) A bigger chance for a reynolds fork to
be near its modulus of elasticity (sorry if i've misused the term
here), allowing more road shock to be absorbed (also perhaps some more
road shock can be absorbed in the rear due to a longer butted area in
the rear triangle) and also (b) more traction on the front wheel and
therefore more predictable steering control.

You are exaggerating the effect. An additional couple of inches of
chainstay (& wheelbase) don't significantly change the weight
distribution. Your ideas on shock absorption are more whimsical than
anything else, and "traction" and "predictable steering" are fuzzy to
the point of meaninglessness.

Quoted message said:

Also, longer chainstays tend to be associated with loaded touring
bicycles that are generally designed to be more stable and almost
self-propelled.

I'm not sure if this is "guilt by association", or what. It's a myth
that touring bikes are "designed to be more stable". I don't know what
you mean by "self-propelled" either -- electric drive?

Quoted message said:

If that's what longer chainstays do, then I'm all for them.

It's not at all what they do, but it's interesting that today touring
bikes have "long" chainstays, these were "normal" chainstays 10-15 years
ago. The real question is what's the ideal chainstay length (functional,
not style) and what happens when you vary the length significantly one
way or the other. Chainstays at the short limit (as is today's fashion)
suffer from tight tire clearances, tight chainring clearances, tight
heel clearances, chain angles are sharper. Bikes are "tippier",
especially in tall frames, this makes them more prone to "wheelie",
especially on grades, or endo. On the other hand, chainstays at the
other extreme only make the bike slightly heavier (extra chain &
chainstay length). I think fashion is extracting to high a functional
price, and when it does that (platform shoes) it is usually short-lived.