still got brake judder...dont know what to do next.. help please

[mar1b0ro]

Bit of a long one this im afraid....and its starting to really do my head in now...plus i still havent got to the bottom of the problem and its costing me a fortune. About a month ago i had the front and rear brake pads replaced on my S3 for its MOT, trouble is somewhere along the line a previous garage working on my car had forgotten to replace the locking wheel nut back in my car.... the old locking nuts were therefore probably removed with force when the pads were replaced. When i got the car back, even after going through the normal bedding in process, the front brakes developed a judder under braking which eventually got worse and worse.

Believing this was an uneven build up of pad material on the discs, i sanded the discs with garnet paper which improved the problem for a few days only for the juddering to return even worse. So i locate a local garage that skims discs on the car and get it booked in. When they connect the machine up to the drivers side disc, the disc is so far out that the machine wont calibrate so the guy at the garage suspects (correctly as it turns out)that the hub is out of alignment. I can only assume that this was done when the locking wheel nuts were forcibly removed previously. So the long shot of all this is that the hub gets replaced, the discs are skimmed successfully whilst on the car (and are now within tollerance), however even after all this, the car still judders under braking. Its now not as bad as before, and the guy at the garage checked and rechecked the skimming machine in case it was faulty....but its stumped him and he has no idea why its still bad...how can this be??? the discs are now true and have been skimmed on the vehicle so surely this would allow for any error in the hub being slightly out. and the pads are nearly new. I currently have 355mm brembo discs on the car and the guy has suggested that i replace the discs, calipers, pads etc for the standard S3 set up to see if this rectifies it. But why would this help? Firstly i cant see that there is anything wrong with the discs and calipers that are currently on the car,and secondly i cant afford to...anyone have any ideas about what else could cause this???

 

[Pessimus Maximus]

I just replaced the front discs on my car as the previous owner had completely warped them. When coming to a stop especially the brakes would sort of shuffle between normal braking and increased braking on each rotation. Is that what you mean by judder or is it more of a rumble?

If the judder is only when braking and never when freewheeling or underpower then I'd bet on the disc being warped or it could be a problem with the caliper in some way. I'm surprised that removing the wheel nuts would damage the hub though, even without the correct key.

Sorry I can't be much help I hope you get it sorted eventually.

 

[s3dave]

New discs /pads your pads will have formed to the bad disc....sorry

 

[Optimum Tuning]

New discs time and if your going to fit new discs its advisable to fit new pads as well.
Is it the source of the judder definately from the front discs? Try applying the handbrake slightly when driving to see if it is possibly coming from the rear
however usually if its juddering through the steering wheel when braking it is front discs that are warped.
Pads that are formed to the old discs will not give you a judder-this can only be disc/hub related. Is the mating surface between the disc and hub and wheel/hub clean/corrosion free?
Its worth bearing in mind We had a disc skimming machine at a garage I used do some work for and it really is very critical that it it used/mounted correctly - Its only as good as the person using it!
Also worth getting the wheels balanced to rule that one out. These jobs are a ****** some times and best starting from scratch.
You can check disc or hub run out with a Dial Test indicator of course with your wheel nuts on to hold the disc on!
Good luck!

 

[mar1b0ro]

New discs time and if your going to fit new discs its advisable to fit new pads as well.
You can check disc or hub run out with a Dial Test indicator of course with your wheel nuts on to hold the disc on!
Good luck!

But if the discs have just been skimmed whilst on the car and the machine says that they are within the acceptable tollerances, i cant really see how changing them for new would make much difference as these discs should now be perfect. The pads are only max a month old as well. It may be that i have to bite the bullet and initially buy some cheap replacements to see if it makes a difference as i dont really want to chuck more cash at decent replacements if its going to be the same problem.

 

[Pessimus Maximus]

But if the discs have just been skimmed whilst on the car and the machine says that they are within the acceptable tollerances, i cant really see how changing them for new would make much difference as these discs should now be perfect. The pads are only max a month old as well. It may be that i have to bite the bullet and initially buy some cheap replacements to see if it makes a difference as i dont really want to chuck more cash at decent replacements if its going to be the same problem.

Maybe if the warping is severe enough to change the internal structure of the metal running throughout the whole disc (at least in certain places) then even if you skim one side it may be only a matter of time before the 'weaker'/over heated parts start to wear a bit quicker than the rest of the disc and it begins to warp again. I would imagine drilled/grooved discs might be more prone to that as they should cool faster.

At the first MOT garage did you wait while they fitted the pads or leave it with them? I've heard some bad stories about people taking customer cars out for 'testing' and experienced it myself, that could explain why the problem's appeared after having work done.

 

[s3dave]

Is there any play in your steering rack? just a thought....

 

[Mpathe]

have you checked the sliding pins on the caliper, maybe the caliper is sticking on the sliding pins and not moving freely

 

[madmark]

this is what i would do take the car for a run and fell the judder then swap the front wheels with the back wheels and run it again to see if there is any change in the judder this will rule out wheels ,tyres,balancing if there is no change check for play in the steering arms ,ball joints, if no play found replace front discs and pads complete with new ones good luck hope you get to the bottom of the problem

 

[aragorn]

How are you bedding them in?

 

[whitehouse46]

i have the same problem on my b5 1999 1.8 a4...its doing my head in have you solved your problem..ive changed my front discs and pads, while having a wheel bearing done but the judder is still there..only when im coming to a full stop the last few feet and i can only feel it through brake pedal..any one got ideas please.....

 

[aragorn]

Your problem sounds more like ABS activation rather than judder.

Probably a broken or corroded ABS ring or dodgy sensor.

 

[whitehouse46]

sorry what do you mean abs activation?? i did have a sensor changed on the front left a while back when the abs light was on had a vag test to make sure its the right sensor..what would i have to get done???

 

[aragorn]

The ABS system's job is to ensure you retain steering control under heavy braking, by ensuring you dont lock any wheels. When the ABS activates, it pulses the brakes on and off rapidly to achieve this, and you can feel this pulsing thru the pedal.

If one of the sensors starts reading erratically, then as you slow down, usually when your speed drops to 5-10mph, the dodgy sensor can start reading zero, when the others are still registering say 5mph. When this happens, the ABS ECU thinks you've locked up one wheel, and activates the ABS system.

It never flags a fault code, because as far as it was concerned you locked the brakes and it was just doing its job.

If you have VCDS/Vagcom, you can view the output from each wheel speed sensor, and hopefully spot the erratic one by driving along very slowly.

 

[s3_stig]

I have the same problem if I brake hard I don't get this only when coming to a stop slowly
And it's even worse if I brake going round a bend the brake peddle just goes all stiff and hardly brakes at all

 

[LD3]

I had similar experiences with brake judder under heavy braking. Changed the discs (the redstuff I fitted previously were only a 2k in) and all is well again. For the sake of £100 I'd get new front discs and pads.