mmccray

Couple months back I finished changing out the brakes on my 90 C2. Put Big Reds on the front, 993 Cailpers on the rear, Cross drilled rotors all round - ...well almost round. See, I think that's my problem.

Over the weekend, I changed oil and trans fluid. Had the rear wheels off. The rear rotors have a spot worn into the EGDE of the rotor. Appears on both sides of the car. The passenger side appears to be about 3-4 inches long and about 1/16 to 1/8th deep. the driver side only about 2-3 inches and 1/16th or less.

I am totally clueless as to how this got there. It would almost appear to be grind marks that may have been used to balance the rotors, but I surely would have noticed this when I installed them... I think?

I'm totally stumped and feeling clueless... The brakes feel fine, and there have been no unusual noises. So I can't fathom how the grinding occured. For it to have been one spot as opposed to all around the outer edge of the rotor - the rotor would have to have been horribly out of round.

I guess my questions for the list.... has anyone else seen this? Are rotors balanced by removing metal-ie. grinding, from the mfg? Could something from the caliper gouge a rotor to 1/6th inch depth for without making some noise?

Man..... I'm confused. Car still runs great and stops on a dime, BUT....

Marshall McCray
1990 964 C2
1987 944S

Bill Gregory

Marshall,

If it looks like a piece was planed off the outside edge, you're correct, that's was done by the OEM rotor manufacturer to balance the rotor.

mmccray

Bill

Thanks a whole lot. I've really been pulling my hair out over this one. I just can't believe I didn't notice it when I installed them. There simply isn't any other reasonable explanation. Thanks for putting my mind at ease on this one.

Marshall McCray
1990 C2
1987 944S