Judder under Braking

Guest · May 4, 2004

When braking I have been getting a judder through the steering wheel and brake pedal of my 1998 C2. I replaced the front discs and pads but it hasn't gone away. Before I go to the expense of replacing the rear discs, does anyone know of another possible cause. p.s.
It only happens at high speed. Stops below 70mph.

Andrew

Guest · May 13, 2004

Andrew,

I get exactly the same thing on my C4S, mine's done around 10K miles. I also had the same problem on a previous Boxster. I believe (thoughts welcome) that it could be any of the following:

1. Warped discs - I believe this can be caused by extreme changes in temperature?
2. Corroded discs - discs obviously corrode when not being used regularly (or hard enough to clear the corrosion)
3. Worn bearings...

My car's going into Porsche Centre West London for some warranty work in a couple of weeks and will get it checked out then.

Any other thoughts would be apreciated!

Justin

Guest · May 28, 2004

I had my 996 serviced recently and I has reliably told that the 996 disks are prone to going espeically of the car isn't used that much. They tend to go on the inner sides where you cant see the disk. I have been quoted between 700-900 to replace all disks and pads.

Stefan

ArBee · May 28, 2004

I have had this work done twice, once on a Boxster at Paragon (Pads and discs on all four corners) at £900.00 and the front discs and pads on my C4 were replaced by Mid Sussex Porsche two weeks ago and the bill - £590.00 (discount on parts as a club member!)

Guest · May 29, 2004

Nothing comes cheap with this thing! Guess I'll have to bite the bullet and change the rears aswell.

Andrew

Rodney Naghar · May 29, 2004

Here's an excellent post by GreigM a few months back about warped discs and cheap pads

http://www.porscheclubgbforum.com/fb.asp?m=51685

"If you go for the standard pads and discs from http://www.type911.co.uk they can sell a full set of discs and pads front+rear for around" (in your case) £328+Vat. And they are very easy to fit yourself.

Guest · May 29, 2004

Thank for the site name Rodney. Is there anything that will catch you out when changing the rear discs. I have changed them on other cars before and its quite easy, but I was a bit worried that it might be a bit more complicated on this.

Andrew

Rodney Naghar · May 31, 2004

Actually I dont know,I've never done it myself but I've heard it's simple. I'll be changing my pads in a few weeks for the first time, I think the only problem might arise with the brake pad sensors, but other than that looks simple.

Guest · Jun 5, 2004

Hi guys.
This is what i recently read concerning the problem with corroded discs.
Lot of porsche owners wash their car then put her away in the garage. Water gets in between pads and discs. This causes the corrosion. Advice was to take her for a quick spin to "dry" the discs and pads out.
Hope this helps all.
Bry.C
C2

timhum2002 · Jun 5, 2004

I don't wish to appear cynical but these mostly seem like explanations from bar room experts.
Loads of people wash their cars and put them in the garageand then use them again with no problem, why should it affect a Porsche differently? I can't possibly see why corrosion affects the inside of the disc but not the outside. I have seen surface rust on the discs of my 993, Boxster and 996 and it disappears a few miles down the road.
Warped discs - a load of old rubbish, discs wear with mileage, they don't warp.
Lack of use may be a problem in that seals etc seize up, could that be the reason.
My guess is that its bearing wear although how that happens in 10k C4s I don't know, If my car were to suffer this sort of problem I wouldn't wait a couple of weeks to sort it out.
Get your car to decent dealer/specialist and get them to check it out, some of them are suprisingly good at diagnosing the cause of problems.

good luck

Tim

Michael Downing · Jun 7, 2004

Hmm.

I would have thought it possible that a Porsche would be more likely to be at risk from washing followed by garaging. After all, is I wash the daily car on Sunday, it will be driven in the next 24 hours. Only so much damage can happen in that time and I would have thought that a quick drive will deal with it.

A Porsche, on the other hand, may come out for a wash and then be left inside for a fortnight. In that time, the pitting could develop to the stage where simple application of brakes won't clean it off.

Anyway, its a nice excuse for heading up the road - "I'm not having fun, I'm preserving the car's value, darling".

blease · Jun 7, 2004

I have just moved up to a 996 from a 3.2 Carrera. I took the 3.2 on track days and the only problem with the braking was a distinct lack. Hot fade got me hot under the collar! I have just got back from taking the 996 on its first track day and to say I am disappointed is an understatement. Basically the thing became undriveable after a couple of laps with severe judder on braking. It would be OK at first, but as heat built up in the brakes, it became worse to the point of ruining the handling. Also, the pad wear light came on. At the circuit, I had the front wheels off to inspect for damage. Calipers looked fine with plenty of meat on the pads. Discs looked fine with no wear lip front or back and no cracks. Then I span the discs through the calipers...fine for part of the rotation but then they would catch in the calipers. On close inspection you could see the gap between the front pad and the caliper close up. This was the same for both sides. So I would really appreciate an expert view on whether 996 discs are prone to warping and whether the problem I describe is warping or some kind of malalignment (as it it bilateral). Also, would the severe vibration damage the pad sensors or their wires and cause the wear light to come on? Incidentally, the car drove home fine. The judder does not appear at road speeds. My car is a 98 C2 cab which is otherwise the muts nuts. Its got 57k miles and a full service history and I note it has had several damper changes. Is this normal?

Rodney Naghar · Jun 8, 2004

Blease, I really think the brakes aren't a problem, rather your driving/braking style.....judder after 2 laps? Maybe you should take some track day lessons. I'm no pro, but I've seen comments like yours many times on many sites, and it usually seems to be a result of the braking style of the driver concerned.

Warped disks are a nonesense as timhum2002 suggested....if you're interested, read the following info regarding disks at this link
http://www.stoptech.com/whitepapers/warped_rotors_myth.htm

blease · Jun 9, 2004

Rodney, thanks for the tips. I have taken instruction on every track day I have been completed and braking style has not been picked up on, so I don't think it is that. I found another forum where someone was bemoaning the same problem at a Knockhill track day. They got a comprehensive reply from a chap calling himself DoctorD who used to be the 968 register secretary. He made some interesting comments about pad material and how it can be deposited on the disc to produce symptoms that simulate a warped disc. I've also had discussion with a Porsche mechanic who states that later 996 pads have a form of balance weight incorporated to counteract pad vibration. So, this is a known problem and apparently quite common. So, can I repeat my request for an authoritative comment from someone who may have further insight into 986/996 brake vibration?

blease · Jun 10, 2004

Rodney,
Sorry, I forgot to say, thanks for the very helpful link. The Stoptech article seems to provide an authoritative answer. Now, next question....what is a good pad for 996 trackday/everyday use?!

Rodney Naghar · Jun 10, 2004

Blease,

Try this link....

http://www.porscheclubgbforum.com/tm.asp?m=26598&mpage=1&key=brake%2Cpads&#26598

vikash · Sep 29, 2004

Hi Andrew

What was the conclusion from Porsche West London ? I have a c4s with 8k having similar problems , the discs were changed at 5k and the problem has re-appeared (8.5k)! I shall book the car back in !

is that its bearing wear although how

vikash · Oct 8, 2004

Hi Justin

What was the conclusion from Porsche West London ? I have a c4s with 8k having similar problems , the discs were changed at 5k (replaced warped discs) and the problem has re-appeared (8.5k)! OPC are now telling me that the discs have rust spots and they are going to charge me to have them skimmed. I am acually contesting this as we speak. Did you have any issues ??

ORIGINAL: justinl

Andrew,

I get exactly the same thing on my C4S, mine's done around 10K miles. I also had the same problem on a previous Boxster. I believe (thoughts welcome) that it could be any of the following:

1. Warped discs - I believe this can be caused by extreme changes in temperature?
2. Corroded discs - discs obviously corrode when not being used regularly (or hard enough to clear the corrosion)
3. Worn bearings...

My car's going into Porsche Centre West London for some warranty work in a couple of weeks and will get it checked out then.

Any other thoughts would be apreciated!

Justin

Guest · Oct 8, 2004

vikash,

They said they could'nt find anything wrong with the discs, but I havent pushed it purely because i've been out of the country so getting the car back to them is difficult..
There is definitely still juddering when braking at higher speeds, and I think I can even feel what I can only describe as slight uneven abrasion when i lightly touch the brakes at very low speed; when I get the chance I will take it back to them - sorry I cant be of more assistance, but please let us know how you get on - maybe if we both push the issue we'll get something done.

Justin

Pete B · Oct 8, 2004

To Timhum2002 - believe me, it happens! My 996 was sent in for its DOT and I was failed on the amount of excessive corrosion present on the inner faces of the front disks. The disks were 2 years old/5K miles.
No amount of emergency stops would clear the disks and £340 later (and an MOT cert.) I was on my way.
Lesson = dry off brakes after washing, or better still, don't wash at all (the car that is).
So far 7 months dry! The Rejex has helped.