Brake noise from new rotors

[04cmnthru]

Just put on a set of slotted/drilled rotors. They are from Sports Brakes and have the zinc coating.

During a test drive, I got a noise from what appears to be the right rear. It sounds like a muted scraping that occurs in cycle with tire rotation (that is, each time the tire makes a rotation, I get one scraping sound at a specific point in the rotation). More noticeable inside the car. I am thinking its coming from the parking brake assembly as I did have some trouble getting the rear right rotor off.

BTW -The brakes do feel different and the rotors seem to grab differently - guess they are supposed to with the slots/holes.

Any ideas?
Thanks

 

[c4c5specialist]

Hi there,
The rear ebrake shoe retaining clip may have popped off.
Yes, the rotors will grip the pads much differently.
Allthebest, c4c5

 

[04cmnthru]

Thanks, I will check it out this weekend. FYI, I did talk to Sportbrakes because I noticed substance build-up on the pads. They claim its the zinc wash coming off of the rotor surface where pads make contact and is normal. They also indicated that this condition is temporary (stops after several hundreds miles of driving) and could be a source of the noise - they also said I might feel a slight vibration during this "break in" period as the zinc wears off. Apparently, the noise has the potential of getting worse as heat builds up because the zinc wash is being removed at a higher rate, creating more build-up. The build-up could be creating a spot in the wheel rotation where the condition I am experiencing is occuring. Couldn't pass judgement on what they told me because I just don't have enough information one way or the other. However, it was clear to me that the zinc wash issue exists with their rotors and that they have had to explain it to others too. And given the fact that the forum would likely be filled with angry customers if the condition persisted, its likely to have some credibilty.

Even given all of that, I am still going to remove both rear rotors and check out the p-brake assembly because the Sport brake rep doesn't have the benefit of actually seeing/hearing my problem .

BTW, I want to thank you for your response. This is my 2nd or 3rd post on a technical issue, in all cases, you took the time to give me a response. I appreciate your willingness to share your expertise with the rest of us.

Regards

 

[Terry Holtz]

Hello 04cmnthru.... Could you update us on how the sportbrakes are doing? Did the scraping sound eventually go away? What was the cause? And you're right about c4c5, we all owe him a great deal of thanks.

 

[04cmnthru]

Sure. Now have about 500 miles on the new rotors. Prior to putting the miles on it, I did inspect the e-brake per c4c5specialist and sure enough the retainer clip had popper off. It took a little bit of work and an extra set of hands to get it on correctly (GM must have a special tool). Anyway, that changed the character of the noise. Now the noise is virutally non-existent. Get an occassional (rarely) rubbing sound particularly if the car has been driven in reverse, then parked w/e-brake on, then driven forward. Lasts only a couple of seconds. So I am assuming that the zinc wash is still wearing off.

So, after all of this, I do believe that the noise was a combo of the retainer clip and the zinc wash. From the lessons learned dept, I would now remove the rubber boot on the backing plate and loosen the e-brake so that the rotor comes off easier. Bottom line- I'm happy with the rotors and would do it again.