pic: HiGrips after two events

[JamesCH95]

Originally Posted by marandola316

Surface area does not have an effect the friction. I would think it would lose grip because the tread pattern provides some mechanical grip on the carpet.

Plain and simple: this statement is false, especially when considering polymers intended for traction. Please don't portray a simplification that nearly every physics teacher uses as a fact.

Here is a link to one of the numerous posts I've made on the subject: http://www.chiefdelphi.com/forums/sh...4&postcount=23

It comes down to something called "mechanical keying" in the racecar world (where this sort of interaction is investigated in great detail). Basically as a wheel is loaded more and more the mechanical interlocking of the tire's tread into its driving surface eventually saturates and then the calculated coefficient of friction is reduced as the wheel is loaded more. This isn't a step change, but a gradual progression as wheel load is increased.

There have been teams who've tested 1in wide vs 2in wide wheels and found that 2in wide wheels provide a higher coefficient of friction. There have been teams (including one this year) that test larger diameter wheels as generating more friction, presumably due to a larger contact patch and thus lower contact pressure.