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Date: 1991 

Why do bike racers use thinner tires (for less friction) if the surface area should not matter according to "ideal" laws of physics?

Of course, the whole bike is sliding through the air, and a thinner tire does reduce friction with the air. Racing bikers also use strange postures to try to reduce the air resistance from their own bodies. Sometimes strange helmets too. But actually, there is a form of friction called "rolling friction" between a rolling object and the surface it is rolling on, so even without any air resistance a rolling object does eventually come to rest. I do not know anything about it, but would guess that it is quite different from sliding friction which as Jack L. Uretsky answered does not depend on the surface area involved. Anyway, another reason for thinner tires is that it reduces the weight, which helps everything (less friction, less effort up hills, higher terminal velocity generally, given a constant motive force). Hope that sort of answers the question! Maybe I or somebody else will look up rolling friction too.

Arthur Smith

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