Porsche Enthusiasts Club Forum

When I purchased my 944 S2 in the summer it had some new-ish looking front discs on, There was a small degree of brake judder so I was careful to check the front calipers to make sure they were free and in good condition. All seemed well, however after around 500-1000 miles the judder got worse. The calipers have never given any indication of sticking and I do drive with consideration to these things, I am NOT the stig!

The logical fix was to replace the pads/discs and examine the calipers. I purchased the Zimmerman discs from a very well reputed Porsche part dealer who assured me they are the best quality discs with a view to fitting them myself. Unfortunately time is not on my side so in the end I got them fitted by my garage. All seemed fine so with new discs/pads I was happy again with my new smooth brakes.

After about 1000 miles of varied and careful driving later the judder has returned and is getting worse. I took it back to the garage who fitted the discs and they say there is a “high spot”, though I don’t know how they are measuring it and I don’t know the severity either. The garage say that the discs are faulty as there is no sign of the caliper sticking or of excess heat build-up or “blueing”.

I spoke to the parts dealer who tells me that they must have been fitted incorrectly. The garage tell me they used copper slip (as they always do) and I trust that they know what they are doing. The dealer says that due to using copper slip they can’t have been fitted correctly to the instructions and that is the problem.

I have also done quite a bit of research on the topic and there are lots of people who have had similar issues of brake jusdder with new discs (not specificly Porsche people) and it has been traced to the rims being refurbished. I can’t really see why this would be but it appears quite common.

So before I pay for MORE discs does anyone have any experience of brake judder with refurbished rims?
Has anyone had any issue with Zimmerman discs and/or copper slip?

If I’d got the garage to supply and fit the discs then it would be their problem, unfortunately I purchased the disc and they fitted them, neither supplier nor fitter want to take responsibility.

Any experiences or theories are welcome.

Thanks.

Are your discs new, or refurbished? Your post is ambiguous about this!

The reference to copper grease is a bit of a red herring. If your garage was conscientious they would have used some on disc to hub interface (just makes it easier to remove disc in future), and if your S2 has fixed calipers you should use a little copper anti-seize on metal edge of pads where they move on pad support sliders. I don't understand the dealer's comment that "if they used copperslip they were fitted incorrectly".

If the judder was eliminated with new discs, and has now returned and getting worse, then it really sounds like pad deposits are building up on the discs, and/or the discs have been allowed to get wet and not dried off (Zimmerman's are very fast to rust), but any rust should be cleaned off with first braking application.

My first resort would be to remove the discs, and scour both sides with wet and dry paper to clear any deposits.

Hi StratfordShark

Just to be clear, the discs were brand new when I purchased them.

It sounds like they weren't bedded in properly, i had the same issue with my 996.

Some very hard braking down a long mountain pass, has cleaned the discs up and the brake judder has not been a problem since.

Gosh - I haven't heard of Zimmerman disks on here for a good few years. They were generally regarded to be poor quality and very prone to warping after a short time - which is exactly what you are suffering from. I assumed that they had gone out of business (or were still being sold under a different name.)

You need to have them tested by a garage with a Dial Test Indicator (DTI). This will tell you whether the disks are true or not. If they are not then the next test has to be without the disks and using the DTI on the hub. If the hub is true and the disks not then send the disks back to the supplier and ask for a refund. If the hub isn't true then you have bigger problems.


Oli.

What Oli said.

I reckon it is the discs myself. For discs I would only use genuine or ATE, although Pagid have been fine on other cars for me in the past including the odd trackday.

The garage would have inspected/measured your discs with a run out tool.

'Warped discs': frequently talked about, but seldom, if ever, seen.

What is almost always dismissed as a 'warped disc' is actually a material build up on the discs surface.

Juddering brakes S2s is quite a common problem.

Juddering brakes on S2's are indeed a common problem (and presumably just as common on Turbos, given that they share much the same braking hardware.) However I don't agree that warped disks are rarely seen; I've warped at least one disk on my S2 in the last 10 years, although it's true that I have had symptoms of warped disks on other occasions that have turned out to be other things.

While a garage should test disks with a DTI they commonly don't, either because they don't have a DTI or they simply don't know how to use it.


Oli.

Make sure the contact faces between the hub and the new disc are spotlessly clean. Do not put copperslip here, it will have the same effect as dirt and get on the pads eventually. If your new discs have become distorted you can have them lightly skimmed. Do not keep your foot on the brake after a heavy stop, use the handbrake, the heat will be much higher where the pads are gripping the disc and distort them as they cool, common on automatics! hope this helps G.

One hell of a Thread Dig I appreciate, but I have a similar issue with Front Wheel Judder under Braking on my 968..

Did you solve this issue Marcusj..?

Yup me 2, it’s the third set of horrid cheap Pagid disks from euros, they last about 300 miles then they warp as they heat up, one stop will be fine the next will vibrate your hands off,

Shit.. Really..?? I bought Pagids from ECP too.. Is that the issue..??

Seems to be in my case

My next move was GSF Premiums as they are made by Zimmerman

60% / £100 Off "Premium" Disks today too.. Worth a punt I guess..?

https://www.gsfcarparts.com/601po0200