Disc Skimming B7 Audi Rs4

[manual_daniel]

I just realised that I meant to post this in the "RS4 Brake Judder" thread instead of this one - it would be more relevant. Sorry. Hope it helps anyway.

[RossDagley]

Well, I'm 300 miles in and the brakes are great still, including some very high speed slowdowns where I've really relied on them! No judder still. Pulled the pads out this lunchtime to check wear and inspect the disc/holes etc. All looked good - in fact, I'd say that blockage of the holes was far less than I was expecting (although I think that's down to the pad material).

[CharlieD]

Got the pad sensor light come on the dash, looked at my discs and they definitely have the "lip" around the outer edge, with some grooves in, presumably from the metal pins in my oem pads

Going to order a set of EBC Redstuff pads and and give Marcus a call

[davebirl]

Just as an FYI to others.

My RS4 had 26k miles on it when I bought it. Drove perfectly for 3 months and then I started to feel a tremor through the steering wheel when braking at all speeds down to 40mph. My buddy also bought an RS4 same time as myself and the same thing happened to him but his tremors were much worse than mine.

He bought new RS4 discs (big bucks( and I got mine skimmed.

My skimmed discs lasted 3 months and I felt the tremor return again.

We both live and work in town so we both do a lot of short stop driving.
I've read that the drilled discs don't cope well with this type of driving.
(I do blow out the carbon at weekends)

So I bought the Phaeton discs and swapped over the bells last week, just 400 euro all in for both.
I couldn't justify the cost of new drilled discs and then have to wait and see how long before the issue returns.

I've spoken to another RS4 owner here in Ireland and he went through 3 sets of Audi drilled discs in one year. Each replaced under warranty.
Original Phaeton Disc

Bolts removal

Bell removed from Phaeton Disc

Bell removed from RS4 Disc

Phaeton Disc with RS4 Bell ready to refit

[RossDagley]

Your discs weren't the only problem - simply skimming them (off the car for example) will just postpone the issue. There's far more at play here than that. Right down to equal torque of the wheelbolts etc.

My "skim" has fixed the issue completely on my car (other than a test on track, as I've nothing booked until February now), although that wasn't the only thing done. I'm very aggressive with brakes and it's not returned

[coffey555]

Got the pad sensor light come on the dash, looked at my discs and they definitely have the "lip" around the outer edge, with some grooves in, presumably from the metal pins in my oem pads

Going to order a set of EBC Redstuff pads and and give Marcus a call

Worth checking to see how much material is left on the disc before calling Marcus, if you have a lip you might be close to the minimum disc thickness.

[CharlieD]

Worth checking to see how much material is left on the disc before calling Marcus, if you have a lip you might be close to the minimum disc thickness.

Is there an easy way of checking the minimum thickness?

As it happens I already called him, and sent him these pictures:

Worst offending disc (off-side), has a pretty deep groove:



Near-side has a groove too but its not as deep:

[coffey555]

32mm is the recommended minimum thickness, it should be stamped on the disc.

Use a micro measuring caliper to check the distance between the two actual brake surfaces and not the lips.

Going by the corrosion they have been on the car a while.

That groove on the outside edge of the disc looks a bit strange, if I remember rightly the pins from the backing plate are more towards the middle of the pad.

Might be worth having a look at the calipers to make sure the pistons are moving correctly?

[Ozzyz]

I had new pads fitted to my RS4 the other day, at the same time my mechanic advised I get the discs skimmed so the pads had an even surface to wear down on, I told him to go ahead and skim the discs.
Once I collected the car from him on my way home I noticed a horrible judder in my steering wheel and pedal when I was braking from anything over 40mph, braking from anything over 70+ the judder was awful.
Obviously I phoned my mechanic up straight away and told him, I brought the car to him the next morning and he had a look, it turned out the skimming machine wasn't properly calibrated, a bit of adjusting on the machine and a re-skim and the problem was fixed. It's amazing how much a difference a minor but of adjusting makes. Now the car brakes straight and true from any kind of speed (like it should of done all along really!) I know skimming is only a short term fix for the discs. Not sure how much it prolongs the life by though.

[murph22]

When I had my old car, there was lots of posts on the forum about Brake discs warping, and one of the members posted this article from Stoptech which is
quite an interesting read. It might be of some use to people.


http://www.stoptech.com/technical-suppo ... ther-myths

[CharlieD]

32mm is the recommended minimum thickness, it should be stamped on the disc.

Use a micro measuring caliper to check the distance between the two actual brake surfaces and not the lips.

Going by the corrosion they have been on the car a while.

That groove on the outside edge of the disc looks a bit strange, if I remember rightly the pins from the backing plate are more towards the middle of the pad.

Might be worth having a look at the calipers to make sure the pistons are moving correctly?

Thanks, will check thickness tomorrow.

There's more than 1 pin apparently, here's a pic I found on another forum: