Jretal

This isn't quite on topic as these brakes are on my 4000... but it's the same setup, so figured some of you might have had this issue.

I've been chasing an issue that has pretty much made me want to drive the car head on into a tree anymore. This issue is that I get a metal on metal groaning noise from the pass front caliper when going certain speeds, make sharp turns to the left, and making long right hand sweeping turns.

I took everything apart last night and cleaned the rotor surfaces (230 grit sandpaper on orbital sander), pad surfaces, and applied a healthy coat of antisqueal goop on the back of the pads... and still, guess what I heard! Yeah, right off the bad. THing is, the noise gets less the less brake dust is on the rotors/pads, as when I spray everything down it goes away for a short while. Obviously it gets worse the further I drive w/o washing, etc.

Basically, it sounds like the pads are dragging on the rotors, but the car still rolls easily when pushing and does not jerk to a stop as if the caliper was sticking when rolling to a stop.

So, questino is... have any of you guys ever run into this issue before? If so, what was your cure? Unfortunately I'm unaware of what pads I'm using since they came w/ the calipers. I thought they were mintex red box, but honestly these things bite WAY too hard to be mintexes! I have a set of Hawk HP+ pads for the track, but it wasn't making this noise w/ those pads in.

Another thing to note: If I jack up this wheel and turn the wheel/tire combo it makes this noise during about a 120* portion of the wheel. Sometimes more, sometimes less. If I pull on the front of the wheel and push where the caliper is, the noise goes away. There is no visible play in the wheel bearing when grabbing the 12 and 6 position and pushing/pulling either.

So riddle me this Audiworld... what says you?

Mr. Mom

I had the exact same issue and I ground them down a bit and it resolved the problem.

OEM rotors may be narrower on P-car applications and hence there is no need to grind.



Hope this helps,


Peter

Agent009

Mine did a similar thing. The noise sounded pretty much like a motorboat puttering along.

The root cause was a bad rear bearing allowing the pad to clip the inside groove on the slots very slightly. The resulting contact was the noise.

After the bearings were replaced the pads were then square with the rotors and the noise went away.

Pelican Pete

I'd be driving down the road, around 35-40mph, and my brakes would be "chirping." When I would step on the brake pedal, the chirp went away. It sounded like the caliper was not retracting all the way, and the pad was vibrating in the slot. Oddly enough, it didn't do this at higher speeds -- or if it did, maybe the wind and road noise was louder and drowned out the chirping.

I also never noticed any uneven pad wear. So I suspect it was more of a vibration rather than a pad dragging against the rotor.

I took the the calipers off the car, cleaned off all the brake dust (there was a LOT of dust when i switched to Axxis Ultimate pads), put the anti-vibration backing plates back in (actually I bought new ones), and greased up the moving parts with brake caliper grease. That seemed to fix the issue I had.

Since I fixed three things at once (cleaned the dust, greased them up, and reinstalled the anti-vibration plates) I can't really tell you which was causing the problem. (I wasn't using the anti-vibe plates because I was going to the track at the time, and they made brake pad changes much longer. Without the plates I could change pads in 10 minutes. But more like an hour with the plates in, since the calipers need to come off)

Oh -- I also changed pads. That's FOUR things that I changed. I got rid of the Axxis Ultimates and switched to Porsche OEM pads made by Textar. Quieter, slightly less dust (but still more than Mintex Reds), and no apparent loss of performance.

Hope this helps!
-- P.

Jretal

unfortunately that's not the case. I have it pretty much dead nuts on in the middle... and they have at least an 1/8" gap b/n the pins and the rotor face.

Jretal

Though the potential for the bearing to be bad is there, I'm fighting that idea as it only has like 4k miles on it! Unless it was a faulty bearing to begin with, I dunno.

Both sides make the noise (only when provoked on the driver's side), but the pass side is noticably worse and is def dependent on what kinda load it is getting.

Jretal

I've done almost all what you said.

i don't get chirping as much as i get the groan. and it varies intensity from non-existant to 'I want to ram you into a tree it's so annoying'. It goes away w/ a slight tap on the brakes but sometimes comes right back, othertimes no. This is what makes me think the caliper isn't fully retracting when I let off the pedal, but again, it doesn't show symptoms of dragging brakes either... so needless to say I'm at a bit of a loss.

I have cleaned the guide pins for the pads, put antisqueal on the back of the pads, cleaned the surfaces of the brakes, brake cleaned the calipers, you name it. Only thing I haven't done is toss in my HP+ pads to see if it keeps making the noise. I know it makes the groaning noise when turning too tight, so something tells me it will make the same noises.

Mr. Mom

looks like that's not your issue, sorry I couldn't help.


are the wheel bearing good? No wheel play?

Jretal

wheel bearing is <4k miles old.

It has no play that I can tell, but I can make it not make the noise if I push a certain way on the wheel as I turn it... so that makes me think it might be slightly bad, but not totally... if that makes ANY sense

Only thing left I can think of is that the actual mounting points on the uprights are not quite where they belong, meaning that the caliper is cocked ever so slightly at an angle. Might try bending the taps slightly to see what I can do.

Mr. Mom

or you are experience a bit of pad rub as the pistons aren't fully retracting?


are you using the backing plates?