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Re: Automobile tires and friction

Is this the case for the materials which are used in today's tires?

How do skid marks get laid down? Is the material just ripped off the tires?
How does it then bind with the pavement?

At the race track (drag racing) they lay down layer after layer of tire
material in the burn outs. Since this is often laying 'rubber' over
'rubber', how is this done mechanically if there is no 'melting' going on?
[Shots of the track clearly show that the first 100 m of the track has a
considerable layer of 'black' material. I can remember as a teenager how a
friend of mine was so pleased that he got his '55 Chevy to 'lay down some
rubber' (on a back road somewhere). I was never able to accomplish this
with my '60 Nash Rambler ;-( ]

If you watch the races, once the tires start to slip, they slip
dramatically, and the drivers usually can't throttle down to regain
traction. This can probably be explained by the difference between static
and kinetic friction, but it is so dramatic that it also suggests a change
in the coefficient as well. Maybe not!

Rick

----- Original Message -----
From: "John Barrer" <forcejb@YAHOO.COM>
To: <PHYS-L@lists.nau.edu>
Sent: Monday, February 25, 2002 12:05 PM
Subject: Re: Automobile tires and friction


Tires do not melt when heated (moderately); rather
they soften. Vulcanized rubber is a cross-linked
structure that cannot "melt" unless some of the
cross-links (vulcanization sites) or other chemical
bonds are broken, so the prospect of a liquid rubber
layer seems pretty remote. John Barrere




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