Coefficients of Friction

[Greg Needel]

Originally Posted by sanddrag

Width does have something to do with it on carpet. I saw teams with .75" wide wedgetop tread get pushed around. But I don't think you need to go to 2" wide to get more traction. I'd say 1.25" is about the absolute max you need to go with wedgetop. There is a region where more width will give you more traction but there is a point where all more width does is take up more space.

Friction force does not increase with a larger surface contact. The reasoning behind that is due to the force in between the surface and the wheel, in this case the robot weight. A larger area between the wheel and the carpet would create a larger source of frictional forces, but it reduces the pressure between them. The same force dissipated over a larger area with the same coefficient of friction is equivalent to a smaller area with less sources of friction forces.

Basically since your robot weight is a constant and your CG is basically the same with both smaller and larger wheels, your traction actually does not change based on wheel width, assuming the same traction material on narrow and wide wheels.