If a small diameter rigid wheel goes over a 1" object, for example, the wheel climbs up faster than a large dia wheel. This results in a sharper jolt to the fork and rider than a larger dia wheel, even though they are climbing over the same object at the same speed.
It is also obvious that the wheel will drop further into a hole than a larger dia wheel, and perhaps get caught easier.
Small dia wheels are stronger and stiffer than large dia wheels, they transmit most vibrations better.
It is also possible that to make the bike fold compactly trade offs in performance vs folding were made.
Last edited by geo8rge; 11-05-06 at 10:32 AM.