Why do bike racers use thinner tires (for less friction) if
the surface area should not matter according to "ideal" laws
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.
Click here to return to the Physics Archives
Update: June 2012