In a message dated 96-07-14 14:38:22 EDT, David Dockstader writes:
<< Everyone seems anxious to teach that static friction is greater than
sliding
friction and demonstrate it with objects on ramps etc. Yet, for most of us
car tires are the most improtant application of friction we experience, and
they work the other way around. Anybody have any good demonstrations to
show
a case where static friction is less, to simulate tires? >>
David,
Say more about this. The only semi-pertinent references I found were from
the CRC Handbook of Chemistry and Physics, 1985-1986. They list the
coefficient of static friction for rubber on solids having a range from 1 to
4. Under kinetic friction, natural rubber (vulcanized) on clean concrete has
a kinetic coefficient of 1.02 and on clean bitumen it is 1.07. Both are less
for wet surfaces. I don't know if these materials are relevant to modern
tires. You also have me wondering about anti-lock brakes!