My theory on this issue is the use of different brake pad material, since asbestos is no longer allowed in the mfg. of brake pads. Another thing is vehicles are getting heavier. I had a personal experience with rotors warping on an '88 Chevy S-10 (the factory pads were semi metallic). I had the rotors turned, one to minimum thickness it was warped so badly, and installed the old type non metallic pads. Never had another issue with brakes on this vehicle again and it seemed to stop better. However, you can't get this kind of pad anymore since they went away from asbestos. I recently tried a set of the new type non metallic pads on a Jeep Cherokee and they squealed so bad I went back to semi metallic.
