Judder under Braking

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

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

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

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!)

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

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.

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

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.

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

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

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".

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?

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

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?

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?!

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

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 !

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 ??

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

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.

Pete B Very interesting to read of your experience although I am completely at a loss to understand how it can happen. Surely the same amount of rust forms on the outside as well as the inside of the disc. If the brake pads will then clean the outside after braking why don't they clean the inside, could it be a caliper cylinder problem. I have run a Boxster S and now 2002 C4 and have not experienced this at all. The cars have both been washed with the wheels hosed and then garaged for 4/5/6 days before further use. Yes I do get a coating of surface rust but that disappears after a couple of firm brake applications. Last point, it doesn't seem to happen to any other makes of car, why? yours perplexed Tim

Vikash - go and drive your car a bit more and stop washing it so often you freak [ ] Welcome to the forum.

It happens to our FIAT...[&:]

I was told at the OPC that inspected my 996 before purchase that the 996s are especially susceptable to disk corrosion due to the compound of the disk.

For what its worth, I just changed my front pads and disks. I ordered the parts from Eurocarparts.com. I used this link http://www.bombaydigital.com/boxster/projects/brakes/change_pads/ for help. It was very simple, (first pads and disks I've ever replaced myself) and took me 30 mins per wheel. I saved around £412 on my OPC's quote. Good luck.

Vikash Any further news on your debate with Porsche West London about the rust spots? I have had the same diagnosis from them. The disks indeed look rusty, but the brakes feel perfectly OK. Higgy

Higgy OPC West London advised that my disks required skimming (normally 375+vat), which has resolved my judder. They also referred me to the Car handbook with specfic reference to disk maintenance. I will now make a point of driving the car immediately after washing to dry off the disks correctly.

Thank you, Vikash and Bruce, for the dilemma you have created for me! I must say I am with earlier correspondents on this: how can brake disks rust just by washing the car? I can't think of any other product in history that rusts after one night's exposure to water!

Not unique to the 996 model. The 993 suffers from exactly the same problem to such an extent that it is known as one of the models weaknesses and all OPC and independents see plenty of them. The inner surface of the disks seem to suffer rather than the outer due to the caliper design. It effects low mileage cars most. Washing / not washing, drying after washing or not etc does not effect the problem. The best explanation I have been given is that the disks corrode at a certain rate due to the material they are made from. As long as you use the car a reasonable amount the disks in effect wear fast enough to remove the corrosion and you reach a point of having to replace the disks through normal use before rust becomes a problem. Low mileage cars however rust faster than they wear. You might think a harder, non rusting metal would be the answer but that would then have a negative effect on the braking characteristics Porsche have engineered for the car . Ian.

The disks have a very high iron content. As referred earlier in this thread by Rodney, they work in combination with the metal in the pads, causing a complicated chemical reaction at high temperatures (as opposed to generating friction by being very abrasive). This is how carbon brakes work also. The pad and disk are made from the same materials, and when they heat up they chemically fuse. Steel does not work as well, apparently, but corrodes in the atmosphere less quickly. Irrespective of you spraying with water, iron will form a surface coating of rust very quickly, just from the moisture in the air. So not using the car very often will not make your brakes last longer! Also, when you 'bed in' your pads, you are actually depositing a layer of brake compound mixed with the metals in the disc onto the surface of the disc. It is this that will stop you! If you do not bed in the brakes correctly, you may experience judder, as the coating is not even. Normally you get one massive build up where the disc stops behind the pads when they are extremely hot. In racing circles, you NEVER apply the handbrake after a race (except on Porsches that use separate shoes in little drums, of course), as this is guaranteed to b*gger the rear discs. It is cheaper to buy genuine replacement discs from a reputable factor or Porsche specialist than pay for your old discs to be resurfaced, so why bother? Also, you should put the old pads in to bed in the new discs (that is, never replace both components at the same time).

I don't know if any of you have picked up this month's (November) copy of GT Purely Porsche, but there's a letter in there about this very topic (from a Boxster owner). Vikash - you mentioned West London skimmed your disks, was this under warranty or did you fork out the £400? I take the point that the less you drive the car, the more likely this is to happen, although I've never experienced it before on similar performance car/brake combinations - e.g. previous car was an 02' M3 - with no problems at all. I seem to be reading more and more on this subject with Porsche's - do Porsche accept this is a problem? I had to perform a high speed emergency stop only this week, and I have to say I was shocked by the poor braking ability - which very nearly caused me to pile into the back of a slow moving Metro[ ]

Thanks Andrew for your in-depth explanation , very interesting. I have since bedded in the brakes, seem ok now. Justin, with a bit of gentle persuasion I managed to get Porsche west london to foot the bill as a good will gesture. (The car is 18 months old) Ref "other performance cars" ,I also have a '02 M3 which I use on a daily basis , this stops beautifully !

With the start of the new track day season, I returned to the scene of the crime, Castle Coombe, running exactly the same car barring one thing...new OPC front discs. Result? Absolutely faultless, stonking braking. FINALLY able to give the old girl the thrashing we'd both been waiting for. Moral of the story? First try new Porsche discs. Probably better than a re-skim and certainly better than pattern parts, which I suspected iIhad on the car because the central bell housing had rusted.

About a year ago I contributed to this thread because my low(ish) mileage C2 had been failed on its DOT test because of excess corrosion on the inner faces of the front disks. Since then I have only washed the car once (filthy b***er) but am pleased to report a complete absence of any corrosion on either side of the disks. The car isn't too bad because Scouser sold me a bottle of RezeX and that seems to stop 99% of the dirt sticking - the only bits I wipe down are the sills and the back bumper. Regarding the comments about corrosion of the bell housings at the back of the disks - I found that use of acid wheel wash tended to increase the likelyhood of these components starting to corrode. I also run a Golf which seems to have brake pads made from an especially dusty material so they get filthy. At first I used Wonderwheels on a weekly basis and the bells immediately started to go slightly orange. I've stopped the acid and now use non-bio washing powder solution - this serves a dual purpose as the amount of water I spill over myself seems to have a cleansing effect!