Re: Automobile tires and friction

[Rick Tarara <rtarara@SAINTMARYS.EDU>]

During the 'burn-out' where the drag racers deliberately spin and 'smoke'
their tires (partially to raise the temp and change the coefficient of
friction), they also 'lay down' some rubber on the track.  I can't say for
sure that this is a 'melting' process rather than a stripping process, but
supposedly (listening to the commentators), the traction is better if the
tires start out sitting on the now 'rubberized' surface.  My impression then
is that solid rubber to rubber coefficients are higher than rubber to
asphalt.  Certainly if there IS any melting, a liquid layer would be very
detrimental.  The ultimate trick is to develop the maximum forward force
without letting the tires slip.  Many races are won or lost according to how
closely the driver can come to the slipping point without going past.

The other related question--to pose to the students--would be why have
(Goodyear has now dropped out) tire manufacturers competed to get their
names associated with racing tires that wear out in LESS THAN 100 MILES?

Rick


----- Original Message -----
From: "Vern Lindberg" <vwlsps@ritvax.RIT.EDU>
To: <PHYS-L@lists.nau.edu>
Sent: Monday, February 25, 2002 11:55 AM
Subject: Re: Automobile tires and friction


> My understanding is that the excess heat in racing tires is
> detrimental not because it liquifies the tire, but because it
> solidifies it. The original tire polymers are cured at the high heat,
> changing the coefficient of friction and the flexibility. The tires
> are changed when the curing process has progressed too far.