Annoying reoccurring brake wobble - HELP!
 

Car started getting terrible brake judder when braking on the way home from the annual meet. It became gradually worse until the car was almost undriveable.

Front discs and pads were placed last month by Formula 1, along with one of the uprights (or "hubs" as Audi calls them) at great expense.

Took it straight back there on Monday morning and they agreed to change the pads under their warranty. Got the car back and exactly the same thing is happening, if not worse. It even wobbles slightly when the brakes aren't applied now. F1 said the next step would be to fit genuine Audi pads.


Now, I do remember one of the techs taking me out to the workshop to show me the new discs on the car when they were fitted last month. It was in the air on a lift so the discs were about shoulder height. He put his hand on the driver's side disc thinking it was already bolted on but when he did so, it fell to the workshop floor narrowly missing his foot. Could this have affected anything I wonder?

Or could it be where the new pads weren't bedded in correctly? I'm conscious of holding the brakes on when stopped after braking so the heat from the pads is concentrated to one point on the disc causing warping in the long run but build op of contaminants short term. I usually slowly creep forward in traffic to avoid this now.

Sorry for the long winded post but I want to get to the bottom of this!

When they changed the pads under warranty did they also change the disc's?

Not the second time. Just replaced the Pagid pads with more Pagid pads.

He also mentioned it could be worn bushes. Don't agree with this though.

Can't drive it above 50mph without getting wobble now

Mine suffered this issue for while. I had new discs and pads after which the shuddering started. My independent changed the discs under warranty (although I think that warping is a low probability issue) and also found that the new pads from Pagid had cracked. (see my post elsewhere). The shuddering still occurred slightly over 75mph on braking and that was cured by replacing some of the control arms which had a small amount of play. If yours now shudders without braking then it must be balance or alignment.

It may be that dropping the disc has damaged the disc and un-balanced it. Were the wheel weights dislodged when removing/replacing the wheels? Also replacing the hubs would iirc require alignment check.

That will be your problem, with brake judder 99% of the time its the disc's that are warped and the pads get damaged as a result. That's why the judder has come back so soon after the second set of pads. I would ask them to replace the pads and disc's and then bed them in correctly.

Could very well be bushes, quite common cause of brake wobble on Audi's under moderate braking. It's usually the bottom curved arm bushes.

As stated above, mine was a combination of factors and, if the bushes in the lower control arms have some play, then that will make any shuddering worse even if it is not the cause of it. That was why even when the new pads/discs had cured 90% of the shuddering, i still some at high speed braking. The issue of warped discs has been discussed before and the likelihood of such an event seems to be considered as low if not unlikely. Unless of course someone has hard, physical evidence of warping occuring? (I am happy to be open minded on this)

I've also read that warping a disc is a pretty unlikely event - just how hot would they have to get to warp that much metal anyway?

I had a long running battle with this too and, whilst I agree that bushes are a likely candidate for the cause of the problem if it's shuddering when you're not braking, other factors may be in play, as David suggests.

My problem started after I'd had new discs, refurbished calipers and new pads. It was great for 2-3K miles, then the shuddering started and got worse. New discs and pads under warranty cured it, but the same happened again after 2-3K miles. And again!

The cure was to get the discs skimmed in situ. They weren't warped, just not quite in line for whatever reason. And it was confounded by a rear caliper seizing a little. Been fine now for at least 15K miles.

You could get your garage to do a run out check on the disc's and that will confirm if the disc's are warped or not. At least that will rule this theory out or in.

I would start with getting the wheels properly balanced, as I said before I had similar problems on the way to the meet recently, very severe shudder under braking and shudder and noise whilst driving. Proper balancing solved it, however I do have issues with both front wheels being "bent" which the wheel balancing chap pointed out so I still get a very slight wobble at a certain speed, but nothing under braking since getting the wheels balanced again. I had mine balanced when I put my summer 20s on a few weeks back but they had managed to go out again in a short time, I can only guess weights were lost on the journey as it got worse on the way down to the point where it became un-drivable.