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Seemingly incurable judder

Adom

Member
Joined
13 Apr 2004
Messages
19
Help!!!!!!!!!!!!! I've had my '96 993 c2 for approx 8 months now, and had a bloody annoying judder from the rear of the car for most of that time. I am now nearing the end of my patience and want the problem sorted. The background: Bought the car from a Lexus garage, they replaced the rear discs but with non-OE parts. Drive for approx 1,000 miles then notice a juddering sound and feel coming from the rear of the car, this appears to get worse when the brakes are warmed up and is only really noticeable above, say 70 mph. Take the car back to the garage, they skim the discs and everything is OK for a few hundred miles. Then the problem comes back, I get angry and demand new discs, they oblige but again with the non-OE parts again. I am less than happy and voice my concerns, but go along in the knowledge that they will provide OE discs if the same happens again. The same does happen approx 1200 miles later. I then - very frustrated - take the car to local Porsche Indie, who says the pads are low and look as though they are not set properly. He replaces pads all round (calliper plates are apparantly OK and not rusty) thinking that this could be source of problem. I pick the car up and he says he has tested it and its sorted. I drive it away dial up 85 mph, brake, and there is the juddering.

Now I'm sick and go back to Lexus demanding OE discs for the rear. They then oblige and provide two lovely grey painted OE discs. These are fitted and it seems to cure the problem. That was until Saturday when I noticed the problem coming back again. Now it is just as bad as before.

A couple of points: I have always felt that the car suffered a slight 'wobbling' at higher speeds from the rear. On smooth roads it feels almost like the rear wheels are out of balance and when the brakes are applied, it accentuates the wobbling to create the judder through the pedal and my arse. Most people don't seem to notice the 'wobbling' when I tell them but I know it is there. In the course of the various investigations, the wheels have been off and balanced, then stripped down and re-lacquered. I have also recently replaced the rear tyres, so its not some form of tyre abnormality.

I am struggling to believe that the discs are the problem. The last 1200 miles I have done I have not been hard on the brakes, in fact a lot of the miles have been motorway and I've been bedding them in. The most confusing thing however is that when the discs have been replaced, the problem is cured for a while. If it wasn't the discs then surely the problem would be there even when the new discs were put on. Unless of course something is working loose that is subsequently tightened up when the discs are replaced. In which case, should I get someone to take the discs off, then put them back on again to see if that makes a difference??? The problem is that I am really grasping at straws because I don't know enough about it. My dad is wondering whetrher it could be play in the bearings, or imperfection in the hub (but then why would it be OK for 1200 miles??), but again, we don't know, and neither does my mechanic mate who has two 911s and works on them a fair bit. The indie I took it to doesn't know, Lexus don't know - nobody seems to know!!

As you may have guessed, this post is borne out of sheer desperation and I appeal to all you people out there who know these cars like the back of your hands, to share some thoughts as to what it could be. I hope I have explained it enough but please tell me if it isn't clear. Many thanks in anticipation.

Adam


Migration info. Legacy thread was 20081
 
It depends on how you use the brakes, if you put the handbrake on when it's hot, some of the brake pad material may get "printed " onto the disc, and every time you brake, it will judder. I had this problem with a set of newish pads and discs and thought it was warped disc, but after a track day, using the brake hard, it's as good as gold.

The other thing you can try is to get a proper 4-wheel alignment done by some one who really knows about 993. With the Kinematic-toe-in etc it's quite sensitive to alignment change, that might explain the unstable rear end. Also check the shock absorber, most OEM shock would be shot by now.

Hope it helps.




Migration info. Legacy thread was 20084
 
I had a similar problem on my 964 and it turned out to be a buckled wheel rim. Its definitely worth getting the 4 wheel alingment checked and it may be worth getting the wheels dynamically balanced (but only if they're true).

good luck

Migration info. Legacy thread was 20086
 
Thought it could be pad transfer too - however I seldom use the handbrake, and do not leave my foot on the brakes at standstill after a hard blast. I am pretty kind to the brakes and am sure that if this was the source of the problem, every single other 993 driver out there would experience it too. Using them hard does not seem to clear the problem in any way.

I have just had the rear wheels aligned at the Newcastle OPC and it is going back to have the front suspension stripped down in order to be able to align them too. The car has done nearly 60k miles so I'm pretty resigned to the fact I will be replacing the dampers in the near future.


Migration info. Legacy thread was 20088
 
Thanks gents - I thought it could be a buckled wheel too, and that was why the wheels were sent away to specialists to ensure they were true. Unfortunately this doesn't account for why the problem is cured for a thousand miles or so. Maybe the full alignment will sort it but I hold out little hope.


Migration info. Legacy thread was 20089
 
Sorry to hear about your problems, you must have paid a fortune for all this work.

Migration info. Legacy thread was 20186
 

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