[cruzin2]

Each manufacturer will list what is the minimum thickness of the rotor either before or after turning them. This thresshold should not be breached even for road use, let alone track stuff. My recommendation is... when you have deep groves in the rotors, consider changing them out. You should be able to get a few sets of pads on a single set of rotors depending on usage conditions. More at a track then on the road. On the road, pads tend to wear more closely to rotor wear. Track seems to burn up pads quicker. If you find yourself using pads too quickly on the track, consider a more aggressive pad. You may be putting more heat (higher temp) in them then they were designed for which can remove pad material quickly. (When I went from a larger track with spaced out high speed stop zones to a smaller track where you were on the brakes constantly, we had to change pads or see significant wear. )