Quote Originally Posted by StraightSix
A runout test will show rotor warpage, but not if the rotor is out of round. I've never heard of a rotor being out of round.

BMW, Mercedes, VW, etc. rotors are typically made from a softer steel than domestic rotors. As a result the rotors do wear during normal use, however, they do not need to be replaced when the brake pads are replaced. I nearly always "pad slapped" my BMWs, and seldom had any problems.

I also do not recommend turning european rotors. Any time we did it at the shop where I used to work, it caused problems.
The heat from turning them is probably more than they could handle, haha