Coefficients of Friction

[JoelP]

I'm in the process of designing a 2 speed transmission for team 1155 the Sciborgs. One thing I need in order to design a transmission with adequate torque and for other calculations is the coefficient of friction of the wheels. However, we unfortunately do not have the resources to purchase different sets of wheels and experimentally determine the coefficient of friction.

So I've come to ask assistance from the chiefdelphi community. Since contact area is independent of the coefficient of static friction, wheel size and number shouldn't matter correct?

What is the coefficient of friction for a 130lb robot (I hope they don't raise the weight limit next year.) on standard FIRST carpet (I hope they don't change that either.) with normal kit skyway wheels?
with Colson wheels?
with IFI traction wheels (roughtop/wedgetop)?
with polyurethane wheels (any specific durometer)?

Perhaps this can be turned into a sticky for other teams to reference if a good amount of data is collected?

Thanks for any help!!