| Steve,
The laws of physics regarding friction says that the frictional force only depends on the coefficient of friction between the two surfaces - and the force pushing them together. Surprisingly, it’s independent of contact area. So different hard rubber blocks (that weigh the same) on a steel plate will begin to slide at the same point, no matter how big the contact patch.
So, if that’s true then why do dragsters use such big tyres?
Well, as it turns out, a soft rubber tyre on a road surface behaves differently than say a hard rubber block on a steel plate. In fact, a dragsters acceleration is greater than what you would predict if the coefficient of friction is 1.0 between tyre and road - that is, no slipping whatsoever.
How is this possible?
The explanation is that the soft rubber molds itself to the small peaks and valleys of the road, interlocking with it. A dragster’s tyres will actually lock into the road, propel the dragster forward and JUMP to a new position, over and over, allowing it to appear to violate physics. Cool eh?
If you think about it, when you lay down a strip of rubber, what you’re really doing is shearing-off a layer of rubber. So the shear strength of the compound controls the level of forces generated, not the frictional coefficient.
[Edited on 9-29-2004 by Shazaam!]  |