2001.5 S4 with stock brakes.
Just installed zimmerman front rotors and hawk HPS pads. Took it around the block for a test drive and it was making a lot of grinding noise and grinding vibrations, all at low speeds (under 30mph with gentle braking). In looking at the rotors afterwards, the coating (zinc?) appears to be wearing off, so i suspect this but need to check. Is this normal with this setup? Should it deminish as the coating wears off?