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Most of that has literally nothing to do with the rotor being warped, it is far more likely to be from pad material embedded in the disc surface and the two are different hardness to either make vibration or pulsing. It is most commonly NOT any warp and checking the discs with a dial indicator will bear that out if somebody knows what to look for.
I could show you a disc cut to within .002" TIR and remove it from the cutting machine and simply put it back on and surprise, it is now out by .005" and impossible to get back to that .002" without much fumbling with the setup. How the parts stores use those crap cutting machines to show customers the 'warp' they then 'remove by cutting', the error is built directly into the machine and not able to get it out. It is a function of the way the machines pilot any parts put on them and built into them. That includes most disc/drum refacing machines out there. The one I used was brand new at the time and I messed with it quite a bit to figure that out.
You can have a 'warped' disc up to .010" out of true and not feel it whatsoever as long as the two disc friction surfaces are within .002" to each other. The caliper then simply moves around on its' float to make the runout disappear, the only runout you feel that has to be super close to not feel it in the car is from side to side of the disc, and why you MUST ALWAYS take a cut on both sides at the same time at ALL times to keep that dead on.
Test for disc warp (pad material in disc) or front ties?............on FWD cars the axles pull forward toward each other under power, pulling out any slack in the ties to not shake, backing off on throttle lightly to become neutral throttle neither increasing or decreasing car speed or LIGHT braking will allow shake to start as the axles are not driven so hard forward, they then begin to fall back and bang back and forth in the tie play to shake the wheel. HARDER braking will then make it stop or lessen, as the brakes fully override the power to axles and the axles then settle back on the other side of the play to quit shaking. If the harder braking still shakes or even more then the discs have pad material embedded in them and need to be cut. A further verification check by jacking wheel up and the tire play check at 3 and 9 o'clock, any looseness there is ties likely.
I got most of that pad embedding info from a brake system technical engineer and have never seen anything disproving what he said. I HAVE as a test of the idea taken 'warped' discs that were discolored in spots (the pad material deposits) and sanded them to throw back on a car and the 'warp' disappeared almost entirely but it took a lot of sanding to get there, the deposits harden and then very difficult to remove them. Cutting the disc removes that upper layer of material and the problem is gone with it but everybody thinks you have straightened a 'warped disc, NOT SO!
Last edited by amc49; 11-24-2018 at 08:31 AM.