Originally Posted by
zzyzx_xyzzy
Many people who have studied bicycle dynamics at the quantitative level do indeed agree that chainstay length should increase with front center. Better designs at least compensate for rear weight bias by increasing the trail, using less fork rake on larger frames. And I can testify personally that YES, large frames DO typically have poor handling the way most manufacturers design them. My most agile, intuitively handling bike has 47cm chainstays.
And the people at Specialized, Cervelo, etc do not understand this, and make poor handling bikes for their sponsored riders. Perhaps the handling charecteristics they are looking for are differnet from the ones you are.
Originally Posted by
zzyzx_xyzzy
Also having a short head tube doesn't explain why the bike is made with a short top tube.
But its a fact, as you go to bigger frames (i.e. longer top tubes) the head tubes get longer and the handlebars get higher. Smaller frames tend to come with shorter headtubes, and the minimum height you can set the bars at is lower in relation to the seat height.
Look at Andy Schleck's bike. He rides with the handlebars as low as they can practically be set on the frame (no spacers, stem angled down) If he went with a larger frame, (and therefore a shorter stem) he could not get the drop he needs from seat to bars.
Its a quite common setup for pro riders, no spacers, stem angled down. A guy riding a bike with that setup can't ride a larger frame size and still get the necessary drop. They simply put on the stem that gives them the necessary extension to the bars.