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Re: Friction



On Sat, 13 Jul 1996 08:47:40 -0400 (EDT) Eugene P. Mosca said:

I recall that when radial tires were introduced into the U.S.
they came with a warning that they should be installed in
pairs and that if only one pair was installed that they be
installed on the rear axle. Perhaps radial tires provide
greater traction so this warning was intended to prevent any
lock-up of the rear wheels during heavy braking, an
occurrence which would likely result in a spinout.

This recommendation was more to prevent oversteer in cornering. The
sidewall of a bias ply tire introduces some tread distortion in braking, but in
cornering it will lift part of the tread right off the road. The greater
flexibility of a radial sidewall allows the tread to sit flat on the road
greatly improving cornering traction and tread wear.

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? Quite honestly, I
think this is another case like the half a lens, and tides, where well
intentioned teachers who are out of touch with the real world mislead their
students. In this case wrong ideas about friction could lead to an accident.