John K

Has anybody felt a slight grinding when braking even with plenty of brake pads left?
Over the last two days I've noticed the sound and feel (both subtle, but definitely there) of worn pads but I checked the pads and they are still very thick.
Is there anything else that could cause this?
The pads and rotors (drilled) have about 7K miles on them.
Thanks for any help.

MikeF

If you're using metallic pads (Metal master?), it is possible that it's perfectly normal...just annoying. If they are OEM pads, I'm stumped.

Bill Gregory

Interesting...I've noticed this too just recently (really only variable here is cooler overnight temps in the 30's) when first going out in the morning. As the brakes warm up a bit, the grinding sound goes away. Pads are good, rotors are worn but within spec.

John K

Thanks for the responses. I removed a wheel and checked the pads one more time. There is plenty of material left. I guess I'll just have to live with the sound/feel until it's time to replace the pads. They still squeak like crazy but according to some of the posts it sounds like this is nothing to worry about.

Bill Wagner

John:

I would look for the following:

1. Bad dampers (seems they like to break off)
2. Corrosion behind the backing plate of the pads.

Is the noise ALWAYS there, or just after the car has been wet???

Bill Wagner
'91 C4, 23,000 miles

Roland Kunz

Hello

Check your Brembo Calipers 99% they have corrosion problems and need a rebuild.
This rebuild is recomened with every brake disc job. Not from Porsche just from my expieriences on german cars who are used hard and mostly trough the wintertime as well.

Grüsse

John K

Bill, the noise is completely inconsistent. I've heard it mainly when the brakes are warm (not extremely hot) and dry. Does anybody have a rough estimate on a caliper rebuild? Also, is the replacment of the dampers a simple DIY job? The car is driven daily and has 67K miles.
I was afraid I would not get out of this without parting with some $$$

Bill Wagner

Replacing the dampers can be a DIY job, just sort of annoying....particularly if you do it and it doesn't help .

It's been my (limited) experience with the 964 brakes that if the problem is damper and/or backing plate corrosion related it usually results in a squeal, not a grinding sound. Another shot in the dark, but pretty easy to check item, would be to make sure the wear sensors are secured. I suppose if one of them wasn't quite secure it might make a grinding noise, but I don't really know.

One stunt that I've used to isolate noise is to flush the pad/rotor area with a garden hose with a spray nozzle. I noticed that my noise often went away for days after the car had been driven in a heavy rain. It occurred to me that all the water hitting the brakes during wet weather driving was "flushing" the brake dust out. I decided to take a garden hose with a spray nozzle on it and angle it so it's spraying almost parallel to the rotor, and let the pressurized water run between the surface of the rotor and the brake pads. This is done with the wheels on, but you have to postion the openings in the wheels so you can hit them with the water at the correct angle. I'm only flushing the outside brake pads. I've found that I can make the noise go away for about a day by doing this, and I've been able to isolate which wheel was making the noise by doing one wheel at a time (and then confirming it with an audio sensor). DON'T do this AFTER the car has been driven because the rotors will still be hot and you can warp the rotors. Do this before you drive the car. If the noise goes away for a while, to me it implies that dust is getting in the system somewhere. Porsche pads produce tons of dust, which is why MetalMasters are so popular in "eliminating" noise. They're not really eliminating anything, just reducing the amount of brake dust produced.

In my case, the backing plate had come unglued from the pad (I think the original factory job had a glue or a dual sided tape to make contact with both the backing plate and the pad...sort of hard to tell) and corroded a little (not much), and I think that brake dust would get trapped in this area causing the erratic squeal. I've cleaned this up and re-secured the backing plate to the pad, and it seems to work, but this has been done recently, so it may be too early to tell if this has actually fixed anything.

Brake noises on cars with decent pads are a pain to troubleshoot.


Good Luck,

Bill Wagner

John K

Bill, thanks for the advice. I need to wash the car anyway so this will be a good process to test before removing the wheels. I'll let you know the results.

Jeff Curtis

Ha! I read all the way down the posts, thinking someone would "nail" this one!!

John's grinding noise, sometimes referred to as a "whirring" sound - is likely caused by his DRILLED ROTORS!

I too experience this sensation, it differs with brake temps...more when they're cold, I believe.

Most drilled rotors come with that particular warning, "when using drilled rotors, one may experience a whirring or similar sound and a grinding sensation under moderate to hard braking"...while likely not an exact quote, it falls close enough to the little slips of paper included with my Sebro, factory cross-drilled rotors.

I have noticed this quite a bit since changing over to drilled rotors.

John K

Jeff, Thanks a lot for the reply. That makes sense and it is a tremedous relief. All components on the brakes looked fine so it had me stumped. Thanks again.