Brake squeak then screech!

[scam75]

Another one for you.

Since I got my car the brakes have always squeaked a bit. I've been trying to get to the bottom of this with no joy. I now have new discs and pads all round. Rear calipers are fairly new and recently Alasdair and I put a fairly new pair of front calipers from a 993 on the front. These have the same size pistons as the stock M030 ones that came off. There is zero plate lift as the backs are quite new and the fronts were stripped down and cleaned before putting on. The calipers are all moving well and not seized at all.

Now i get the same squeaking as ever and on top of that I get a nasty screech when the brakes heat up! Aargh![]

The only things not new are the brake shims. I have two different types on the front, neither of which are stuck to the pads and not in great condition either. Each front caliper has one that looks like a bit of card with two solid circles which go in the pistons and one of the sticky type which was recycled from an old pad (not stuck any more, plus one has a circle thing missing!).

The question is, do I, A: Chuck the shims away and go without them. B: Chuck the shims away and replace with a new matching set. Or C: Don't bother the problem isn't the shims!

Answers on a postcard please!

Stuart

 

[Alexw]

A) Well you could take them off and try it without the shims? if it gets worse, put them back on!

B) Those shims are pretty expensive, IIRC you can only buy them per piston and theyre about £4 each I think...

C) It probably isn't [] I remember a post a while ago about exactly this, the noise is actually the pads vibrating very fast so it sounds like a screech. Have you put copper grease on the backs of the pads? When I sorted my brakes last year only the fronts had those shims, I can't even remember if I put them back in or not..... I put a load of copper grease in and on the piston and on the back of the pad, don't get it anywhere else though in case it makes its way to the brake surface.

 

[Super_Marv]

The shims should be stuck to the pad with adhesive - they're not doing their job if they're not. You'd be better off taking them out. If it still squeals, then it's more than likely the pads themselves which are causing the squealing.

 

[scam75]

Thanks guys. I will ditch the shims in the morning and apply some copper grease on the pistons and rear of the pads.

Stuart

 

[Hilux]

Throw the shims over the hedge and use copper grease on piston face and back of pads.

Also if the pads are tight when cold they wont release so imagine when they are hot, they wont move unless forced to by the piston so `ease` the pads where they rest in the caliper with a mini grinder or file as required.

The pads should always be loose in calipers with only the springs restraining them (again, remember they will expand with heat).

With billet calipers etc you can hear them rattle over bumps, annoying but re-assuring that they arent sticking.

My PF97 pads rattled a lot [8D]

 

[scam75]

Quick update. Shims now over hedge and all pads nice and free with copper grease on the piston faces and rear of pads. Went for test drive and no noise at first, then a couple of tiny squeaks when heating up then nothing at all when heated up fully. Horrible screeching has gone when warmed up and annoying incessant squeaking when coming to a halt has disappeared.

All in all a good result. 2 rear pad sensors broke a bit when coming out but both reseated ok. Will order a couple of replacements up.

Incidentally, I had no shims at the back, were they only for the front or did they have them all round from the factory?

Cheers for the advice

Stuart

 

[Alexw]

Yeah, 2 of my sensors broke when I took them out, I didn't bother to replace them though, I'll know when they're getting low as I have the wheels off often enough!

I'm glad that sorted it out for you!

 

[dirtydirtyharry]

A word of caution. Mine squeals like a pig. I have no shims. I greased the backs of the pads and the sqeal stopped for a few days but it then come back. I have done the same again with exactly the same result - the noise returns after a few days.

 

[scam75]

OK, the noises are returning. I seem to have my incessant squeak back and the occasional squeal thrown in at low speed stopping. If I get some heat into the pads they are quiet. Problem is with normal driving thet pads stay quite cool and I get noise when coming to a halt.

At present the front pads are quite loose, minimal effort with pliers will take them out. The back ones are a bit tighter although a firm grip with pliers and a bit of wiggling brings them out. Does this sound normal or should I be filing the pads till they come out by hand? Or again, is this not the problem?

This will drive me demented! [:'(]

Stuart

 

[zcacogp]

Stuart,

The pads should move freely into the callipers when fitting them. If they aren't, find out why. (I'm not saying this is the cause of the squeal, but it could be relevant.)

Filing the sides off the pads is a botch. If the plates are lifted, you need to take the callipers off and cure this. There is another thread going at the moment about how much this costs to have done, but it is not an unreasonable DIY proposition.


Oli.

 

[scam75]

Cheers Oli, I have zero plate lift though. New calipers at the back and recently refurbed on the front. I have new discs and pads all round and the pads slide in and out no problem, with pliers though, not fingers. I think Hilux had mentioned making the pads free to the point of rattling! That's what I was alluding to.

Strange thing is they stop making noise when heated up, surely they have expanded by then? Confused.

Should there be a liberal coating of copper grease on the sides of the back plate or just the back plate itself? I put a little bit on the sides and plenty on the back and pistons. That seemed to cure it for a couple of days.

Stuart

 

[zcacogp]

Ah. OK, ignore my comments then.

When I use copper grease I put it on the back of the pads, and on the edge of the pads.

One trick to stop pads from squealing is to grind off an angle from the leading and trailing edge of the pad face. If the pad face (onto the disk) looks like this:

| |
| |
----------


... make it more like this:

| |
\______/

(with apologies for crummy ASCII art!)

Take the edges off at 45degrees or so, and a fari way back. Yes, you will reduce the pad area on the disk slightly, but the pressure will increase correspondingly and you shouldn't have any noticable reduction in braking efficiency, and it should stop the squealing.

What pads and disks are you using?


Oli.


ETA: Bah, sorry, the spaces in the ASCII art didn't work. I hope the diagram makes sense ...

 

[scam75]

Cheers again Oli.

I have mintex pads on the rear and pagid on the front. the discs are ATE I think.

I will put more copper grease on the edges and see how we go, failing that I will try the chopping technique. Incidentally, however did you come up with that?

Stuart

PS. The ASCII was poor! Appreciate the effort though!!

 

[Super_Marv]

Hi Stuart,

Are both front and rear pads squealing, or is it just the pads on one particular axle?

The OEM Pagid's have a reputation for squealing. Though saying that, they're fine in the rear of my car. It sounds like it's more of a pad problem now. Though it's not unusual for pads to squeal for the first thousandish miles, when they're new, then go quiet.

Marv

 

[zcacogp]

Scam,

As Marv said, Pagids are occasionally known for being noisy.

Where did I hear about the technique? I can't remember. I should add that I have never done it myself, but have heard about it from a couple of different sources. In fact, some brake pads are supplied ground as described to prevent this when fitted from new. Google Images came up with this, which is helpful:

I don't know what they fit, but the chamfer on the sides is what you are trying to achieve. (How you grind this off is a bit of a mystery. I guess an angle grinder would do the trick, or a file and a bench clamp.)


Oli.

 

[scam75]

If I knew that I would be closer to fixing it! I convince myself it's the front, then the rear, then left, then right, all part of the going mad process.[&:]

The front pads and discs are only weeks old (along with the calipers) and the noise was the same before and after.

The rears were done about 6 months ago by RPM who according to the receipt I have just looked at replaced the rear discs and re-used the pads with a clean up. Again same noise was evident before and after the work. I seem to remember blaming the front at that point. So only the rear pads are not new (which I thought they were). They are definately Mintex pads with plenty life on them.

I will try different pads in the back I think and see how that goes.

Stuart

 

[Big Dave]

Well i think youve just answered you own question, by telling us your using Pagid pads.
Thats THE reason for the squeeling.
They are actually Porsche OE fittment + they squeel like a pig too.
If you were to fit some other make , like the Mintex or dare i say it "green stuff" i think youl find therle be no more squeeling....
I have had LOTS of different makes in my car , + found most of the "NON" pagid pads are ok.
Pagids are THE best for races / track days in there "Blue or Orange" form, but not realy for the road...

 

[sawood12]

When I first bought my car they had OEM discs and pads on. Braked great in all conditions, wore well and didn't make any squealing noises and had no signs of brake fade on my first track day when the pads were pretty much getting on for needing replacement. When they came up for replacement I went down the usual aftermarket pad route - not necessarily because I needed them but because it seemed like the done thing to do. I tried two different types and they both squealed like pigs and were no way near as good as the OEM set up. Lesson learned - Stock Porsche brakes are better than most Porsche drivers - unless you are a big-time track day monster, or race your car then stick to stock! The discs don't corrode and the pads don't squeal or chuck out a load of corrosive dust that welds itself to your wheels and bodywork and stop you pretty well - better than most aftermarket pads for normal road use. Porsche know a thing or two about brakes.

 

[Big Dave]

Scott.
" Porsche know a thing or two about brakes".
They may well do, but that doesnt stop them from making pads that sqeeeeel...[][]
Ive even had this out with Barry + Grant at Hartech, and they say the same... Its the Porsche OE / pagid pads....
Try some ATE or Textar. they might be ok..."Euro car parts"...

 

[scam75]

Thanks guys

The incessant squeak has been ever present but the loud squeal has only been since the Pagid's were introduced. This may be no coincidence.

I am going to change tha back ones tonight and see if the incessant squeak goes away and I think I will attack the Pagid's with Oli's angle grinder idea. If that doesn't work they go in the bin. I nearly deafened myself today braking in the underground car park at work with the window down. Talk about embarassing![]

Stuart