Originally Posted by
sunv
I was wondering if this tight clearance applies to road bikes too. Like if I buy a fork that is straighter (less rake) and slide the rear wheel closer to the seattube, I would achieve a shorter wheelbase. Would this also improve the handling of the road bike?
My guess is that I would get alot of toe overlap (more than the track bike), since road bikes have slacker seat and headtube angles.
But this would be interesting to try to how the handling changes.
It depends what you mean by "improve." It will make the bike twitchier and more responsive but less stable, which is desirable for a criterium or track bike but undesirable for a touring bike. On a road bike, you would be more likely to have toe overlap but not because of the slack headtube angle (a slacker HT angle would increase the wheelbase and move the front wheel away from the BB) but because road bikes have longer crank arms compared to track bikes.
Criterium-specific road bikes (do they even make these any more?) have tight rear triangles, steep HT and ST angles and low-rake forks because they are designed to be responsive and maneuverable in close racing formation around fast, winding criterium courses. In essence, they are track bikes for the road. Pursuit track bikes, on the other hand, have longer wheelbases and shallower angles (the question of rake is complicated because they use 24" front wheels), which makes them more stable and allows the rider to stretch forward into an aerodynamic position. Pursuit bikes aren't meant to be ridden in close formation, so they don't need to be maneuverable. In essence, they are time-trial bikes for the track.
Sorry that none of this addresses the question of frame clearances. As for the rear wheel, a tight rear wheel clearance will also get an aerodynamic "draft" effect from the seat tube, which is also achieved in some Al/CF track frames by using a teardrop shaped seat tube to get closer to the wheel. Tight front wheel clearances allow for reduced wheelbase and trail which makes handling more responsive, but there's another reason the clearances are so small on track bikes: When you apply the front brake on any bike, the braking forces cause the front triangle and fork to bend (more or less depending on the stiffness of the frame, weight of the rider, etc) which causes the front wheel to approach the downtube. Hard braking on a tight bike with oversize tires could cause the front tire to touch the downtube, which would apply an additional braking force, and cause the frame to bend more, force the wheel harder into the downtube, etc. etc. positive feedback loop, which would immediately lock the front wheel and probably cause you to have a pretty bad crash. Track bikes can afford to be built with tighter clearances because (a) they're stiffer anyway and (b) they don't have brakes- although the rider's weight still moves forward in a deceleration, the deceleration is more gradual and limited by the fact that the rear wheel would probably become unweighted before the braking force flexed the front wheel into the downtube. OTOH, has anybody seen those bolt-on keirin brakes being used on super-tight NJS frames? I am pretty concerned that sooner or later one of those riders is going to hurt themselves pretty badly when their front wheel gets jammed up during a panic stop.
... was that long enough?