[sanddrag]

Years ago we did some friction testing on 968, but it was far from scientific. Our primary goal was to determine how much of a role wheel width played on friction with regards to maximum pushing force. In the past, 968 had run rather skinny wheels (as skinny as 5/8" tread width). We made up two sets of wheels with tread (and I don't remember if it was wedgetop or roughtop). One set was 1 inch wide, and the other set was 1.5 inches wide. We installed the narrower wheels and filled a plastic container with batteries so it was quite heavy and experimented with having the robot push this container on carpet. We then added more weight until the robot could no longer move it. We then swapped out the wheels for 1.5" wide ones and gave it another go. The robot pushed it with no problem, and it took adding something like another 40lbs to the container to make it un-moveable again.

While not very scientific, we did determine that wheel width can play a substantial role in friction.

Beyond that, the only thing I really bother to do each year is press some wheels against the ground while simulating turning them and think to myself "yeah, this grips well." I know, not very 'engineer' of me. If the need arises in the coming season, perhaps I'll have some students do the test you describe.