[Sears]

Hi all, I've got a bit of an annoying problem that I can't quite figure out and am hoping for some direction. My '92 coupe (tiptronic, dammit) will make a bit of a grinding noise/vibration when I apply the brakes hard (not slamming them, but applying them briskly, like when you run up on a yellow light). What confuses me is that if I brake very lightly it won't do this. The brake system is in good shape, theoretically. Pads don't have many miles, fluid is fresh and at the same time the fluid was flushed and filled, I had SS brake lines installed.
Any ideas?
Thanks in advance.

edited to add in that it is more of a vibration/feeling that it is a noise

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[PhilG968]

I've had similar issues on and off on my 92.
I have it down to pad composition (this set of Porsche pads from the dealer), nothing serious, but a little annoying from time to time.

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[Sears]

Gotcha. That makes me feel a bit better. They are Porsche pads in fact.
Thanks for the feedback.

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[Lonestar968]

Same thing I've been experiencing for a while. I attribute it also to crappy OEM pads. The brakes will throw you through the windshield but the "grinding" sound on hard braking and constant squeak squeak squeak when poking along in town freaking sux!

Big Reds coming right up. Soon.

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[Sears]

i get the squeak squeak squeak too...our issues are apparently the EXACT same.

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[Ryan]

Sears, were the pads/rotors broken in correctly? Visit stoptech.com for a good writeup on how-to do it best. If you have a uneven coating of the pad transferred to the rotor, you will get a pulsing or vibration due to this. It is often though that the rotors are warped, but no it is the improper break-in.

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[Sears]

Ryan, I doubt the brakes were broken in as I would do it (same as described on shoptech.com) but I do not believe anything is warped, there's no pulsing sensation like I've experienced when driving my friend's cars that do have warped rotors. I think it's just composition, as it isn't 100% consistent. Usually doesn't do it until the brakes are warm.

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[Pauli]

Raising my hand also for the SQUEEK, SQUEEK, SQUEEK - yes, it does suck! At first I just figured new brakes, this will go away. That was 450 miles ago and having them looked at on 3 occasions w/ no change. Going through town is the worst - you would like to think that the people looking are appreciated the lines of the car, not looking at what's attached to the sound of the brakes!

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[flash]

rotors almost never warp - it is almost always diagnosed as warping when in reality it is deposits - the stoptech site explains this quite well - in 30 years of doing this i have seen a grand total of something like 3 or 4 truly warped rotors, all on under-braked race cars or tow vehicles

noises would not be from warping anyway, and if they were warped you would absolutely feel it - it is impossible to hold the steering wheel still if it is a front rotor, and if it's the back the whole car shakes

noises are from an uneven trailing of the pad over the rotor - it takes less than .001" of deposit to cause noise or vibration - think of it like air passing over a reed in a flute - there isn't much you can do about it either - the pads will likely need to be changed and the rotors surfaced or replaced

it doesn't matter how new the stuff is either - i've screwed up pads in less than 100 miles

this happens because of either impatient break in of the pads (as i said, i've done it myself), or super heating them at some point (done that too) - contaminants also will cause this - it takes very little oil or other chemicals getting on them to cause noise

i have noisy brakes on the M3 - nothing i can do about it until i change the pads and rotors - we've tried the graphite stuff and we've manually scuffed them - no soap

you can try a very aggressive set of semi-metallic pads, 220 sandpaper the rotors, and go run a few laps and try to scuff the rotors, and then install new pads - i have about a 1 in 3 success rate with this - it's a lot of work though, and at that point you might as well just change everything

make sure you don't install a semi-metallic or track pad for a street car if you want things to be quiet - the quietest pad i have found, without the nasty heat and dust issues of OEM has been the porterfield R4S

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[Sears]

good info, thanks flash

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[flash]

lol - while i've found this all over the years from doing it, it's all on the stoptech site - it was nice to see the validation though

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