Murray

My rear brakes started squealing quite badly a little while ago; at low speeds and gentle braking. They are LOUD!

The rotors are new last fall - drilled and slotted
The brake pads were new at the same time - Metal Masters. Everything was quiet for a month or more then started squealing.

I have tried the following:
- spraying stop squeak on the backs of the pads
- chamfering the leading edges
- cleaning and lubricating the calipers
- light sanding of the rotors

None of these made a significant difference. I thought maybe they are just a noisy compound, so I switched the pads out for a new set of Jurid pads. Still squeals, but now dusty as well.

The good thing is that now I can swap out a set of pads in record time, but the noise is making me crazy. I'd like to resolve the noise before leaving for SITM.

Any ideas?? Do I need to take the rotors in to a brake shop and have them checked/ turned??

Mike Frye

Have you checked the parking brake shoes? The rears have pads and shoes. Pads for normal braking the disks and shoes on the inside of the rotors for parking brake.

Murray

Do the e-brake shoes engage when the brake pedal is depressed. (actually I think I am the one who is depressed ;-))

I will check them anyway.

Mike Frye

No, you're right, if that was it, you'd probably hear it all the time or at least not just when the pedal is pressed.

Unless maybe the brakes aren't applying evenly and it's changing the geometry in there or something...

Any chance you can get the car up on liftbars or jack stands and turn the wheel while someone else applies the brakes? If they squeal every time you should be able to isolate it that way.

terry gt

Do you have the porsche damper pads installed ? Have you tryed changing the brake fluid , could be a little air in the system .

Murray

Brake fluid was flushed last year along with all other fluids. I do not have the porsche damper pads installed. The fronts don't either and they are quiet.

Dave928S

Drilled rotors can be noisier, particularly with normal DD lighter brake application. What are they like after repeated heavy application? The standard system is very front biased .... could be that changing the rear bias valve might help with your setup.

A bit of a stab in the dark as you seem to have explored all other logical steps to fix so far.

Murray

They get noisy when they get hot. First couple stops they seem ok. Then after a while they start to squeal. They don't seem to squeal in reverse, but I haven't really tested that to any extent.

Bill Ball

I'm the lucky one. Mine don't squeal and I don't have the vibration dampers installed. I have Axxis Metal Masters as well and some unknown drilled rotor. The only thing I've done that might be different is to put some antiseize on the bottom tab that the pad rides on as well as the backside of the pad. if that fails, you might resort to the vibration dampers. Also, some have reported corrosion lifting the endplates away from the inside of the caliper. The pad back fits between them and when lifted it makes it hard to fit the pads. Perhaps that can contribute to squealing too. Try coating any points where the pad back plate makes contact with the caliper parts, being careful to avoid the pad friction material, of course.

Also, did you follow Porsche's recommended bedding procedure? I can't say that it will help. I don't do it either - it's rather brutal, at least if you complete the second part. But if I had problems like this, I would try it.

Dave928S

Then I'd be inclined to go with what Bill is suggesting ... as drilled rotor dust squeal I've experienced is less when you pound the brakes and get them hot.

GlenL

I suggest less aggressive pads and intentional break-in....as above.

Murray

Wow that break in procedure seems harsh. I did follow the break-in process that was provided with the pads but it was not that aggressive. Repeated breaking from 50-20mph.

This evening/tomorrow I will try the following:
- remove calipers and rotors (I'm getting good at that)
- inspect the e-brakes
- remove end plates and clean underneath them
- sand down the rotors a little more aggressively than last time
- reassemble
- put some anti seize on the end plates where they contact the top and bottom of the pads.
- try the porsche bedding in process.

One thing that does seem odd is that my right rear brake gives a very light squeal when gently turning left like a lane change.

Murray

I have tried Metal Masters and Jurid. Both are street pads.

Bill Ball

First, removing the endplates is none too easy. If they are flat against the caliper, skip it. The Allens that hold them on are often a b%^&*h to remove.

If you get squealing in turns without the brakes applied, that is odd. How are your wheel bearings? I mean, the rotors should not move relative to the calipers unless the wheel hub is moving (it shouldn't). The rear bearings are not adjustable or repackable like the front, but you might want to check that wheel for wheel bearing looseness. Usually these bearings start making horrendous noises before they get loose. Also, I would check that the pads are retracting as they should. If one pad wears more than the other in a pair, that could indicate the piston is not moving freely.

Murray

The end plates have lifted a bit. Sprayed some brake cleaner in the gap and got lots of brake dust out of there. Maybe I'll just try and clean out some more so the pads fit in a little easier.

The wheel bearings appear fine. The sound seems more like the inner pad is making really light contact with the rotor due to centrifugal force.

If none of this works, I'll see if DR has the damper pads available and I'll pick them up during SITM.