Squeaky brakes

Hi I'm a new member, and also a new owner of a Porsche. I have just bought an early 2005 Porsche 996 C4S Cab, which is fantastic. However, I do have a slight concern about the brakes squeaking. I bought the car from an Aston Martin dealership, who had taken it in part ex. Before the deal was done I got Porsche to do their 111 point check on the car. This was all fine, except they said the discs were corroded slightly, and recommended replacement discs and pads on front and rear. The dealership I bought it from agreed to do this for me prior to the sale, and they bought the parts from the OPC and did the work However, I have now done a couple of hundred miles, and occasionlly whilst braking I get an awful screech from the discs. This isn't under heavy breaking, just normal pressure whilst slowing for bends, lights etc. Sometimes it's quite quiet, sometimes LOUD! Is this normal whilst the pads and discs bed in, or do you think it is indicative of something else? Many thanks indeed for any advice offered Ian

Did they put a coat of Optimoly grease on the rear of one of the pads. I understand you only need to put it on one of them... Theres certainly a few knowledgeable folks on here when it comes to brakes so I'm sure there will be some good advice along soon. Personally, I'd take it back and get the dealer to sort it.

Grease on Porsche pads? No, no! That's what the adhesive shims are for! Sounds like you need to re-bed the brakes. Light braking puts a shine on the pads and shiny pad surface against shiny disc surface results in poor braking and screech. Do a few heavy braking sessions to deglaze the pads

My bad, just read the technical manual and it says no grease. However, where I did find it was that it is sometimes used on RS29 pads... So don't do that.

Thanks for the advice guys, I'll go out for a spin in a bit, and see if some heavier braking sorts it ! Cheers Ian

No problem. RS29s are thicker, too thick to fit with shims in place, so Plastilube et al is used. Personally I've replaced the shims when sufficient wear allowed them to fit again

I would recommend, taking the pads out, and ensuring that the housing area of the calipers where the pads sit are clean and that the pad slides in easily without any binding. Rub the pads down on a block of steel on emery cloth just to rough them up before refitting. Check too if the discs are worn so that there is a ridge around the edge of the discs. If there is you may need to chamfer the outer edge of the pads to help it to clear this ridge. The problem may also be that having pushed the pistons in the calipers back to fit the new pads, the pistons may be a little sticky in the new position as a result of dirt or corrosion, and this may be causing then to hang up and not auto retract when you come off light braking. If you can work the pistons a little by pushing them back into the bores, then letting them come back out onto the pads under presure this may help too. Anyway that my 2 cents worth, which has stood me in good stead in the past with similar issues. Regards Big Bob

Totally agree with Big Bob. You may also find that they didn't install the shims. Get the dealer to show you their invoice. No shims = squeaking. I know this because it happened to me, easy to fix at the dealers expense. Wellcome to the forum Ray :bandit:

Hi, I have a copy of the invoice, it shows 4 discs, with pads, 4 warning wires, and 3 sets of 4 damping plates. Are the damping plates the shims? Occurs to me it seems a little off that there are only three sets of plates, not 4, or is that correct? Ian

Yes, I bet they greased the back of them rather than making use of the adhesive nature of them. The rears use spiders, I can't recall if they come in single pack per axle but it wouldn't surprise me.

Thanks for the advice guys, will let you know the outcome Ian

I don't believe damping plates are shims. I think the plates are the springs that hold the pads in place - sounds like the reaon your brakes are squeeking to me. BTW, the shims look like aluminium discs about 20mm diameter and 10 mm thick. There are two of these disks on the inside pad and two on the outside pad, and of course on both wheels. The front shims are where your problem is as this is where most of the braking force takes place. The rear shims look completely different. Ray :bandit:

Not on a 4S Ray. The damping shims on a 4S/Turbo are two milled aluminium cylinders that are attached to a 4"x1.5" metal plate with an adhesive material on the other side that sticks to the pads. The rears use two spiders attached to 25mm discs each side of the caliper, these spiders are assymetrical ie. you need one small, one large. These are also adhesive on the reverse, again to stick to the pad. I'll try and dig out some pictures.

Right. My turn. I installed RS29 fronts and RS14 rears and new rear discs at the same time (left the Alcon front rotors in place). Issue. Unbelievably loud squealing from the rear at light brake applications. I either had to slam the brakes on or use the handbrake in stop start traffic. We're not talking little typical metal pad squeal but god awful, hear me from 300ft down the road type. Highly embarrassing to say the least! Solution? Well.................. I didn't use shims initially and initially there was no noise. About 100 miles it started and wouldn't stop. I agree there is little to no room to fit the rear shims - note the shims are round discs that clip into the pistons with an adhesive backing as previously mentioned. Also note they are sized differently as the leading edge piston is smaller and therefore has a smaller shim. I had to file a small amount (tenth of a mm) to get the shims to fit and it was not easy. Standard pads would be much easier. Did fitting the shims fit it straight off? Nope! It persisted for another 50 miles or so. Why do I think this is? Well maybe the shims wouldn't have helped at all and the discs and pads just needed to bed more? No, I actually think the pads needed time to groove / bed to the disc better to stop the vibration. By fixing the pads in place with the shims I believe it allowed the bedding to happen properly rather than the pad moving around. It's only a guess and maybe in time the pad would have improved. The fronts also have a shim setup the sticks to the pad however I am not using this. The shim consists of two ceramic inserts that are stuck to a piece of sticky material. You bond this to the pad. In my case I believe JZM have removed the sticky but left the ceramic discs behind. I just left them in the pistons and changed the pads. They are not noisy. This applies to the 6 pots but I think the 4 pots might use the same sticky disc setup as the rears? That is my experience and what I did to cure it. I hope it has been at least a little useful. Oh, and the rear shims are ordered singularly (I know as I thought they would be pairs and had to order more!) Jeff

4S/Turbo/GT3 Mk1 4 pots use the plate I described. The rears are single spider shims of different sizes.