Advice needed on replacing discs and pads

I have been advised by the local OPC that the surfaces of my brake discs are 'breaking up and the car is not completely safe to drive' !!!!! Needless to say they have recommended new discs and pads all round. On inspection I have noticed some very fine surface cracks in the discs, so I guess the time has come to change them, as it would appear a bit more serious than the usual corrosion issue. I notice Design 911 have kits with Serbo discs and Textar pads at reasonable prices, and so am tempted to go for these. Am I correct in understanding that these are the manufacturers of the OE parts, and that the parts are the same? Has anyone had experience of them? Also I seem to remember that somebody did a run down on the procedure for changing these parts complete with the torque settings for the bolts. Can somebody point me towards the thread? Is there a workshop manual that I can get hold of? I am pretty comfortable working on cars (and bikes) but there is nothing like having a reference, or insight from somebody who has done it before. Any advice appreciated Cheers Bill

My front discs are getting to the stage where they need to be changed also. The OPC told me in January I needed to change them but 2 independent Porsche Specialist said that I didn't need to. Basically, they said watch the cracking, try to keep the holes clear to assist in ventilation and when the cracks start getting bigger than 5mm then it's time to consider a new set. Just remember OE discs don't necessarily mean they are Porsche Discs or even approved by Porsche. They just mean they are from an Original Manufacturer, i.e. Bosch, etc Hope this helps.

Ray Nortway just supplied and fitted two rear discs for £295.44 inc vat.

Pah, Resb, they're only just run in! I change them when the crack runs from end to end Seriously though, all of those cracks are pretty much called surface crazing / heat crazing. It's scares most people and allows Porsche to sell more discs.... Read here for an example. The cracks shown above are not a reason to replace. Give them a skim and if they are gone after a skim you're fine, assuming there is enough meat to skim them within the min thickness.... http://www.winnard.co.uk/service_guide.htm I would not be the slightest bit phased using the above discs. I've had much worse!

That's good to know. I'll keep em for a while longer in that case. :thumb: I must admit though my braking performance is not tip top at the moment hence why I have sort of convinced myself they need changing. I must say, even the independents never used the term "crazing" so there you go. Garages, always out to fleece you.

7 times out of 10 the discs in those pictures will end up failing an MoT!

Valid point. :!

Tell me about it, I've still got a pair of front 4S/Turbo fronts that have only 8k miles on them (4-5 track days) that might benefit from a skimming....I doubt it though!

Yes, they may fail an MOT because the MOT person is uneducated. That can't be helped unfortunately, however they don't need to be thrown, just skimmed in that case. My discs were mentioned on my MOT as an advisory and they are quite crazed, much like above. I would therefore conclude that the MOT agent was educated Crazing can turn to fissures at which point you much change them. Much like it says, too long or deep, change the discs. A good indication is if after skimming they remain then they are passed their best..... There is obviously nothing wrong with changing your discs if you don't like the cracks or are worried about it, but I'm just giving the more realistic side of it.

Thanks for the info guys, insight much appreciated. I had a quick look at mine (thro the wheels) and it would appear I have the occaisional crack similar to the heat crazing example from the Winnard references, rather than lots of small ones radiating from the holes. I'll take the wheels off and have a closer look to see how severe they are close up, and check they are just on the surface. It'll have to be tomorrow when I have more time, but will keep you posted Thanks again Bill

On closer inspection with the wheels off it would appear that the comment from the OPC related to severe corrosion on the inside of the disc (which is really quite bad on the fronts) and not to cracking. Skimming the discs maybe an option to clean them up depending on what the minimum thickness allowed is Can anyone tell me what the minimum thickness for the front and rear discs is?

The Porsche Discs do rust like crazy, they really do, so you can understand what the dealers mean I suppose. Is it just surface rust? I don't know but it certainly looks more terminal than surface rust. Sorry can't help you there Bill. Hang on...let me look at the workshop manual and see what it say's, if anything? [edit] Nope, nothing in the tech or workshop manual...

Bill. In answer to one of your questions, Serbo and Textar are the OEM manufacturers. As well as the discs and pads, you'll also need a pin kit for each axel and a set of caliper bolts.

The discs on the front measure 26.6mm and the rears 23.0mm. From Renntech it would appear that the limits are 26.0mm for the front and 22.0mm for the rears. I suspect the rears will clean up within the tolerance, but not the fronts so I think I'll bite the bullet and get new discs The upside should be much more positive braking!

You want to see some of the 911's used as track toys, they are far worse. Talking of MOT inspectors being uneducated, I have practically new Toyo R888's - i got an advisory "All four tyres close to legal limit". Tsk Tsk