Porsche Enthusiasts Club Forum

Hi guys, got a problem with my 964. When i bought the car it had warped front discs so i changed them for sebro ones from euro car parts. About 3 months later the car started to vibrate when braking, so i checked the front discs by removing the wheel and rotating the disc. There seemed to be a high spot on the discs as they passed easily through the pads then went stiff in the same place each time the wheel was turned. I returned the discs to euro parts and they changed them for new ones. I fitted these super carefully making sure there was nothing between the discs and the hub. These have been perfect for about 3 or 4 weeks until saturday when the vibration returned when braking. I went out in the car again on monday to check the tyre pressures and get some fuel and the car was fine until i was heading home when the car started vibrating each time i used the brakes.
I dont think it could be the hubs or it would vibrate all the time.
I removed the wheels again and the discs didnt seem to pass through the pads evenly, has anyone had these sebro discs from europarts and had trouble with them or could it be somthing else?

I have Sebro discs on my 968 and they have been fine.
Are you sure that you cleaned all of the corrosion off the hub before you fitted the new discs?

Also, are your pads free to move in the calliper?
I think that 964 callipers are of the same generation as the 968 ones, so could be at risk from plate lift just the same.

I'd be tempted to run it over to Tom Fergusons or Car Tech and Care and ask them for their thoughts in case there is something that you've missed.

Sounds to me like pad transfer. You'll need a dial gauge (DTI) & a magnetic stand around £25 from Fleabay or somone like RDG.
Clamp the stand to the upright or something firm & then set the DTI so the pointer runs against the disc. You are looking for minimal run out certainly better than 0.1mm. I suspect you'll find the overall run out is OK but one area will have a rough area where pad material has transferred from the pad to the disc.
Check the pads aren't binding in the callipers & overheating the callipers. Also NEVER sit with your foot on the brake after a hard run, this are the most common reasons for this problem.

Have you ever had the calipers re-furbed?
I cant c 2 sets of discs fu@kin up, unless there manafac is poor.
All 64 calipers are v old, and do corrode like mad, this causes tons of problems.
Mine where that badly corroded that the pads wouldnt fit in the caliper!

Get a DTI and run it on each disc. I suspect brake material or a warped disc. probably the former.

If the car is lightly used it could be corrosion in the calipers/pads, if you can give the car a good hard thrash, really using the brakes hard, see if it makes any difference, it sure would not be the first time it was a cure.

Hi guys, just an update on my vibrating brakes!
Used a dial gauge and magnetic stand and found the drivers side hub was running out 0.16mm, so i got an engineering firm to skim the hub perfectly flat, they also confirmed it was running out.I re-assembled everything and to my suprise its no better.The vibration comes through the steering wheel but not the pedal. As the car slows after pressing the pedal the judder starts.The wheels have been balanced and the car just mot'ed last week with no issues.The callipers are working fine also. I checked the wishbone rubbers by levering them with a screwdriver, the back rubbers had no flex in them but the front ones were a bit softer? I'm going to get a lend of the dial gauge again to check the discs but i am running out of ideas, anyone else got any?

Possibly the front wishbone bushes becomming soft.

964's suffer from an issue on the front disks developing run out during the initial running in period and replacing the disks multiple times result in it doing the same thing over and over again...

In the 90's Porsche came out with numerous excuses for this happening but eventually insisted that all main dealers obtain an on the car brake lathe (procut) to remove a minute amount of material to true up the disks.

Interestingly as the aluminium hub ages and relaxes with heat cycling the problem becomes less of an issue when the disks are replaced.. but when the cars, or the hubs were new.. they were a nightmare.

Back in the day, no amount of machining of the hubs helped stop the problem.

Often fitting new brakes would be great, until a couple of thousand miles had passed and then the car would vibrate and shake on braking.. run out testing would show a slight amount of run out, often worse when the disks were hot.

Even though we fit a massive amount of 964 brake disks, we had not seen the problem in a couple of years recently, until we had to replace the front hub/bell on a crashed 964, which soon developed a brake judder on just that one wheel.. once the disk was machined on the car, the problem went away and stayed away.

It almost seems like when the hub is new, it has a great deal of stress within it, and at certain temperatures distorts, which loads the brake disk up in different ways, eventually distorting the disk (although with the mass of the brake disk its hard to believe!) and once this has happened and the disk has settled down to the hub, further distortion stopped... which is why machining the disk once the judder starts, stops the issue for the life of the disk.. but once the hub has aged for several thousand heat cycles it no longer becomes a problem.

Beats the hell out of me, and beat the hell out of Porsche all the way through the 964's warranty lifetime.

On the other hand, as someone mentioned, you could be suffering from a little pad material transfer (which isnt often visible as you would expect) or soft suspension bushes allowing the entire arm judder.

No the worlds greatest fan of Sebro, even though I do sell a great deal of them mail order on request, but thats more to do with me selling them cheaper than Euro, than it has to do with their quality, but they are really ok disks (better than Zimmerman)

cheers for the info jon.

Been off line for a while, so thought i would let you guys know wot was happening with the brake judder on my 964. put the car into tom ferguisons porsche specialist last week for a check over. All the front end is fine and tight with no worn bushes, but they did say there was a high spot on the drivers side disc. Euro parts changed them again for the second time but i havent fitted them to the car yet. There dose seem to be quality issues with cheaper parts even if they are OE spec. I havent seen replacement discs from porsche but have been told they are nothing like cheaper OE quality ones and are nowhere near as good a quality.This sort of defeats the object of putting OE on the box??

If you get Porsche disks from Porsche, they should be ATE or Brembo (to name but two) but there are a lot of dodgy parts dealers and online who sell disks as OE or OEM which are not.

One particular nationwide dealer sells OEM disks for Porsche models.. which ARE NOT Original Equipment Manufacturer (OEM) but are in fact made (or repackaged) by a company called OEM. This is a seriously worrying situation as the disks have no connection to the Porsche supply chain what so ever.

The only problem I have with genuine (OE) brake disks from Porsche are the Boxster and 996 items, which seem to have a low nickel content, which results in them rusting very quickly and not having much wear resistance, which is compounded by these cars also having traction control which uses the brakes to stop wheels spinning, causing increased wear.

Be carefull what you buy, there are a lot of lies and con's going on in the parts world right now, with a lot of parts being sold as OEM which are not.

There was also one of the nation wide parts companies who were or still are selling knock of Bosch parts, which come in what looks like Bosch boxes, but are not the real deal and are manufactured in Turkey. Porsche notified me of this a few months ago, but I can't name and shame the company, but needless to say you will all know of them!

Its a shame you can't identify the culprit. I understand why. I wish there was a way of having a list of these dodgy companies as they cause us no end of pain and expense.

This also recently extended to somebody completely rebranding and copying a competitors product! So Jon makes a valid point.

Regards,
Andrew

so how do we know which bits are and which arent?? is this just brakes we are talking about????? worrying!!