[JesseK]

If you are trying to wear your wheels for more traction at a competition: good luck! You will more than likely wear one more than the others, which means one of the wheels probably will not touch the surface. On top of that, it's fairly difficult on this field to keep all four wheels with the same amount of traction if you modify them. (A mu difference of 0.01 with these wheels is a +- 20% amount of traction...)

So, 'normal wear and tear' from your shop -- I wouldn't worry about too much. I'd imagine that the GDC expects that everyone will want to practice ahead of time and that not everyone has an ideal field to do so.