I recently had some guy smooth out my front wheel rotors on a lathe, but now when I hit on the brakes, they begin to pulsate. I guess this guy didn't understand how to face, oh well I should have done it myself. Anyways, I was wondering if there is anyway to tell which rotor is causing the problem, or is it necessary to take off both to see?

Joe

 

Sometimes the wheel will pull toward the side with the warped rotor. BTW it is possible to straighten a warped rotor. But this involves high speeds through very twisty roads