RS4 B7 brake issue

Post by **RichT128** » Tue Sep 11, 2012 10:15 pm

I love my RS4 but brake issues are driving me up the wall - the discs and pads have been changed 4 times in a year (16000 miles total, not down to excessive driving) and Audi have realised that something is going wrong. When pads and discs changed all fine but 3 or 4 weeks later the pads/ discs seem to be warped and the car starts to vibrate on braking. Pads have been bedded in by audi using their procedure for cooking the brakes. Looks like an issue on the drivers side front set.

So far, pads and discs have been changed, engine has been remounted, flanges and hubs changed. Audi Germany is "investigating issues on rs4 brakes" but I can't get more info. Audi uk have run out of ideas other than " fit ceramics for £8,000" - which isn't guaranteed to work.My local Audi team is thinking it could be related to the suspension arm because the A5 had an issue a while back.

Has anyone else had this issue/ any suggestions?

Post by **Myrcin** » Tue Sep 11, 2012 10:43 pm

Did you bed in your brake discs properly? For high performance cars you should always use bed in procedure, something similar to this http://www.apracing.com/drawings/P14.23 ... 20Pads.pdf

You should easily find some useful videos on the Internet.
Hope it helps.

Post by **adsgreen** » Tue Sep 11, 2012 10:46 pm

How the car is driven can also be a contributing factor.
3-4 weeks sounds similar to what I had in a different marque

Post by **Myrcin** » Tue Sep 11, 2012 10:47 pm

This video shows the procedure I have used http://www.youtube.com/watch?v=kd_PtFJW ... ata_player

Don't worry if you burn your pads a little

the most important part of this is to not bring the car to full stop before you cool down the discs.

Post by **RichT128** » Wed Sep 12, 2012 9:46 am

Audi did the bedding in procedure themselves and were completely happy with the results. Car is the family car, most of the miles are clocked up on motorways on cruise control so how it's being driven probably isn't the cause.

Post by **Myrcin** » Wed Sep 12, 2012 10:14 am

I doubt they did it correctly. I have never heard about any service (not only Audi) that carries out a proper procedure. How did your discs look like when you took the car from Audi? Did they look like new? If the answer is yes then it means that they didn't bed them in correctly.
I really encourage you to do it yourself. It worked for me, discs in my Evo are about 15k miles old, including some hard track days etc. and they are still in a very good condition. My previous discs lasted for about 5k miles because of lack of bed in procedure. The fact that it is a family care changes nothing as one hard braking is enough to bend the discs.

Post by **adsgreen** » Wed Sep 12, 2012 10:37 am

We need to consider that these are floating rotors - they have exceptional resistance to warping.
Search for sonny's posts on his track days and how he can chew through an entire set of pads (to the metal!) without any problems with the rotors. The stock rotors whilst not cutting edge are perfectly adequate for the job.

Proper bedding in is very important however it's not hard to do and is unlikely to be the cause after so many repeated replacement discs.

The brakes on the RS4 are massively overspecc'd for day to day driving - you need only a fraction of the contact force to get reasonable braking and this can lead to big problems. If you don't treat the brakes hard enough and just feather them then "warping" is the result.

When you brake from cold (say after driving on the motorway) the only brake force you get is from raw friction between the pad and disc (this also tends to strip off the material you've deposited from bedding in). When the brakes get up to temperature the braking force is generated by the pad material jumping to rotor and this is considerably more efficient than pad on disc contact. This is why braking feels so much better when they are nice and warm - the more track focussed the pads, the more this is noticable.

However if you are too light on the brakes then what can happen is that (even if properly bedded in) the microscopic high spots on rotor are the only bits that contact the pad. These heat up to the operating temperature where pad material transfer starts however the microscopic "valleys" are not hot enough so no pad material is transfered here.

The problem is that once this starts it's self replicating as the high spots get higher and so on. Eventually you have high spots that are so high that when braking lightly the disc feels "warped" as pad material has built up to a point where you can feel it in the pedal and steering wheel. After a few cycles of this the pad material can crystalise into a very hard compound and no amount of bedding in can remove it - the rotors are either junk or need to be professionally skimmed (easier said than done on floating rotors).

I had this on my old vxr8 and because I was used to cars that didn't have such overspecc'd braking systems (generally not servo assisted either) and on track where the brakes were massive you are always using them fully so I'd never personally come accross this problem. 3 weeks and 1800 miles in the vxr8 a set of discs were trashed - "warped" if you like. Next set... same again however this time I did find out about what was going on and got the old rotors in a lab. Under a microscope is bloody obvious that there are patches of this hard stuff on the disc so I was a believer.

Once I found this out I adapted my driving style to avoid this (harder on the brakes, frequent use of threshold braking where safe, not sitting at traffic lights with the foot brake on) and never had an issue for another 20k miles. Same with the RS4 - found the receipt for the brakes and pads and it was 26k miles ago. So probably due soon but still not a hint of a wobble.

Post by **RichT128** » Wed Sep 12, 2012 2:02 pm

Thanks, that's really helpful. Spoke to my local Audi team this morning, who've been in contact with Audi uk. The message coming back is "we're pretty sure ceramics are the only way to fix the issue" - which implies some knowledge of the problem, trying to get more detail from Audi in Germany now.

Post by **adsgreen** » Wed Sep 12, 2012 2:34 pm

Funny, to me it strike of the opposite... They've no idea whats going on and trying to come up with something.

Post by **RS6chris!** » Wed Sep 12, 2012 7:29 pm

Grab the ceramics and run!!!!!

Post by **The_Coat** » Wed Sep 12, 2012 7:40 pm

Are the ceramics going on for free

Post by **adsgreen** » Wed Sep 12, 2012 7:42 pm

RichT128 wrote: " fit ceramics for £8,000"

I guess not.

Post by **RichT128** » Thu Sep 13, 2012 1:29 am

No, they want me to pay £8k and won't guarantee the results!

Post by **RichT128** » Fri Dec 28, 2012 1:11 pm

Got to conclude this by saying hats off and thank you to Audi - in the end they did it under the enhanced goodwill programme and got to a place where I put in some cash, and Audi uk/ listers made up the balance. Couple of months on, it seems to have fixed the problem, the brakes work well and look immense!

If anyone is looking to use an Audi service centre in the Midlands I can't recommend Dave Lea who runs the Listers centre on waterey lane middleway in Birmingham enough. All the way through his attitude was "don't worry, we will get this sorted and I won't leave you in the lurch".

Post by **HYFR** » Fri Dec 28, 2012 5:36 pm

So u got ceramics?
How much did u chuck in?

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