That is exactly correct. Rotors don't warp in a traditional sense, but run-out occurs because of pad deposits. I rarely resurface rotors anymore, because the tolerances are so small. Most people use a micrometer on a rotor BEFORE they resurface it. There is no certain way to determine how much material must be removed before putting it on the lathe. The time to mike a rotor is after it has been resurfaced. If it is even close to the minimum thickness, I would discard it and get a new one. These days manufacturers make rotors as thin as possible to try to save weight for mileage while still providing enough heat distribution. These days, one can purchase quality rotors and pads either online or at the parts store for a reasonable price. Who wants to have to do a brake job twice, because of vibration. Go online and do your research on brake pads and rotors. You can find dozens of choices at tirerack.com, rockauto.com, ebay, and others. During my auto repair career, I had more trouble with Honda brakes making noise and vibrating than any other, except for 1996-2001 4Runners. Back in the 80s and 90s, Honda made many of their vehicles with rotors that did not pop off. Their recommended method of resurfacing rotors was on the vehicle with a special machine, which I purchased. Along those lines, if one has a vehicle that continually has brake vibrations, the issue might be in bearing lateral run-out, or a slight bit of motion from one side to the other causing deposition of material on the rotor. In that case, the only method of eliminating the run-out is to resurface the rotors on the vehicle with the on-the-car brake lathe.
