mn2trance

I had finally replaced my OEM pads with Hawk HPS at 38,200 miles yesterday after I had noticed this grinding/scraping noise about a week ago. When I took the inside pad off on the driver side, it was completely gone! That was the source of the noise I had heard. However, the outside pad still had some life left on it as well as both the inside and outside pads on the passenger side. Has anyone encountered this before and can explain why the inside pistons would have caused that? My driver side rotor is very smooth with no grooves unlike the passenger side rotor with a small groove towards the outside which I thought would have had that problem.