kansasracer: That could probably be best answered by the fast guys at your track. Factors include track layout, type of cells (2000, 2400, 3000), how long the race is (5 or 8 minutes) and motor (stock or mod). You'll have to base your pinion/spur gear selection on your wheel size (roll out). Most guys true the tires down from the out-of-the-package size. I can't recall what roll out I was using when I raced my CK. However, I do recall using Jaco purple fronts/grey rears, a P2K motor with blue springs and a partially shaved brush. This was while using 2000 cells.