Brake squeal - why?

redcoupe86 · 08-05-2006, 08:55 AM

I have a small issue of break squeal and I would like some opinions as to causes.

First, the PO's records show that the break pads have been replaced and the rotors turned.

Second, the breaks only squeal once the breaks and rotors are heated up. For instance, if I jump in the car in the morning and start driving no squeal, everything is fine, but once I've been driving a while I get this high piched squeeky squeal.

Third, the cars breaks don't make the car pull, nor do they pulse or show any other symptoms of say warped rotors, though this may still be the case I guess.

Anybody have any thoughts on what to look at?

Porsche_monkey · 08-05-2006, 09:16 AM

Rotors are my guess. I personally don't believe in turning them. If they warped the first time they will warp even faster when they are thinner.

You could try the 'adhesives' that go behind the pads and are supposed to reduce squeaking.

I had a terrible problem with sqeeling on my Volvo, I tried everything, but only new rotors solved it.

Nine9six · Nine9six's Garage

When the pads are replaced, you should take a file and break a 45 degree chamfer 1/16"-1/8" all around the pad. You should also lightly grease the side metal edges of the pad.

Bill Verburg · Bill Verburg's Garage

wrong pads
dirt
stiction in the sliding components
poor rotor surface prep
uneven wear pattters in the pad or rotor
loose hardware

k9handler · 08-05-2006, 12:43 PM

I was always told to place a small dab of copper grease on the back side of the pad where the piston and the pad touch...so I do and my brakes have never made a sound.

magic930 · 08-05-2006, 01:17 PM

Some cheap aftermarket semi mettalic pads will also squeal no matter what you do. A higher quality pad may be needed.

Wil Ferch · 08-05-2006, 01:30 PM

I've mentioned my fix before-->

Brakes squeak squeak squeak - what's causing that?

- Wil

redcoupe86 · 08-05-2006, 02:01 PM

thanks guys, I think I;ll try removing, chamfering, grease or taping and give that ago before I shell out the cash for new rotors and pads.

oh, how could you tell if your rotors are warped, whats the testing technique?

Trust Me · Trust Me's Garage

Nine9six is on the money. Exactly what he said.

Nine9six · Nine9six's Garage

With the car jacked up, and the wheel off, put a dial indicator on a magnetic base and turn the rotor by hand. I believe on your model, runnout should be no more than .004"
I did this after having my rotors turned, and discovered that the dufas that turned the rotors did not respect the datum reference (the face that bolts against the hub) when he turned my rotors.
The second time around, I went into the back with him and showed him how to properly set up the rotor, and prepare (stone) the machine face, to turn a set of rotors accurately.

Jeff Alton · 08-05-2006, 08:17 PM

You can minimize run out by "clocking" the rotor and the hub. That is, try mounting it in a few different locations relative to each other. My Brembo GTP's were a bit noisey at first and they had 5 thou of runout. By clocking the rotors I got them down to 2 thou on one side and 3 thou on the other side. No more noise!

Cheers

David · David's Garage

Due to the high temps, I use molydenum disulfid grease between the pad and the pistons.

Nine9six · Nine9six's Garage

Will,
Where do you get this 3M acrylic aluminum anti-rattle self stick material ?

Jeff,
Excellent tip, but this would tell me that the face of the hub is not perpendicular to the bearing axis. I know...its not a perfect world.

redcoupe86 · 11:08 AM

ok, took off the fronts and did the chamfering this morning and did the grease. Couldn't determine the the make of the pad too clearly - something like "Jarpid" - im not sure.

Problem is still there but seems less. One thing I do notice (and maybe this is normal for these Porsches) is that there is a LOT of break dust. For instance, I put new tires on the car a couple of weeks ago and I cleaned the rims inside and out before having them installed. Since then I've maybe put 20 miles or so on the car, and when I took the wheel off this morning there was a layer of brakedust soot on the inside of the rim, enough so that if you blow on it a small cloud of break dust results, or enough so that if you where to lay the rim on its side and tap it with a mallet it would make a ring of dust on the ground.

Now the previous owner had a break job done to the car less than 2000 miles ago. Could this just be how the pads are - squeeky? If so, could I put new pads on without getting the rotors turned b/c its been only 2300 miles. rotors are nice and smooth and so are pads.

If so, what pads do you recommend for street drivig - remember I have stock rotors:

Are these any good?:

Bendix
Textar
EBC (and which color?)

I just need and OEM replacement, nothing for track

2 things to add.

one - the car only seem to squeel the last10 feet of a stop or so.

two - it only squeeks/squeals when breaks are applied - no sound when breaks are not applied.

Wil Ferch · 08-06-2006, 11:38 AM

Jurid and Textar ( German OEM pads) are notorious for throwing gobs of brake dust.....

Axxis ( formerly Repco) Deluxe or more aggressive Metalmasters don't dust very much.... very nice and cheap street pads...Metalmaster can also work for mild track duty.

Can't go by simple brand names alone....need model name too...on the backside of the pads are temp profiles/aggressiveness letter codes like EE, EF, and FF, etc..which gives a clue as to the kinds of brake ( not "break"..) pads these are.

I guess no one read the full intent of my post?... I say there that you probably need to do "all three" things to rid yourself of this problem....chamfer the edges.. anti-seize on the three outside edges of the backing plate.and putting the anti-rattle backing pads on. The 3M / Acrylic stuff I use I found at my FLAPS under the "Help!" brand name label...the guys who make all kinds of aftermarket pieces like window cranks. HQ is in Colmar, Pa ...IIRC...

- Wil