Disc Skimming B7 Audi Rs4

[zedrs5]

Hi All

I dont usually start topics on here but I just wanted to share with everyone the Brake Discs, I've just had skimmed today.

I purchased some Front Brake Discs off Ebay which were practically new they had covered a maximum of 500 miles.

I had them fitted last week with new pads by a local Vw Audi specialist . But on driving I was getting a Judder
at any speeds over 35 mph, it got a lot worse over 50. The steering was shaking on breaking.
The discs were badly warped.

I then contacted Marcus Bailey a Disc skimmer from Cambridge. He got back to me straightaway and said he could do them,
although the front discs on the B7 are semi floating. I was quite hesitant on getting them done as people had told me it cant be done.

The chap turned up outside my house on a saturday morning in Birmingham after a 120 mile trip at 9:30 and began work.
It was the first time he was doing a b7 but had done a few b5's before.

He began by jacking the car up and removing the Caliper and cable tieing it to the suspension. The machine then does its work.
Upon completion 2.5 hours later we went for a test drive, and the car driver absolutely perfect, no judder or anything at all.

Marcus used to be a Gearbox enginneer for the Williams F1 team and I must admit I was well impressed by his service.

He came from Cambridge to Birmingham a 240 mile trip and only charged £130, which isnt even Audi's hourly charge, he saved me £700(Cost of new discs).

I would recommend him to you all.

His details are:
Disc Skimmers Ltd
Marcus Bailey
www.discskimmers.com

[marv]

That's good to know, thanks. I never knew such a service existed!

I guess it's only really worthwhile on fairly new discs, and I guess most new discs aren't warped?

[RossDagley]

Just bumping this as after repeated reminders from Doug about getting this done, Marcus is coming out to mine tomorrow to look at my setup and hopefully resolve the last bit of judder I have.

£60 a disc to skim plus 30p a mile if he visits.

Worth noting that EBC in Northampton (pro-cut disc skimmers) - apparently a "premiere workshop" - said that you can't skim discs on the car when discs are semi-floating. Marcus uses exactly the same machine but can. Tells you something about the recommended workshops on the skimmydiscs website!

Anyway - looking forward to tomorrow.

Will reply her with results after


PS - this is in the S4 forum, probably should be in the RS4 section

[R Black]

I have seen this once before, i think it was on Wheeler Dealers, looks like a great service, one I will make a note of thanks.

[Gavla]

I had this done with Marcus a few thousand miles ago - great price, service and top bloke. Highly recommend if you consistently get the brake judder

[RossDagley]

All done. Initial results are impressive so far. Bedding in (doing 60-20 stops) by the 3rd one you could really feel the bite was hugely improved. I used my existing pads so it will take 100 miles or so before they're fully up to performance as the pad needs to be reshaped to the new true disc.

Of course, the real test is the nurburgring. I'm still a sceptic (that the problem wont come back) but Marcus assures me it wont - and if somehow it does, he'll come out FOC to investigate. Can't say fairer than that.

[TonyHayers]

I've had my fronts and rears done by a pro-cut machine, no problems at all. Only thing they said is that they have to go slower on the drilled discs to avoid heat build up on the cutting tool.

[KernowPete]

I've had my discs pro cut skimmed twice and both times the judder came back eventually. The skim will cure the symptoms but not necessarily what caused them in the first place.

Also we need to get away from this idea of discs 'warping'. I've researched this to death and it is ultra ultra rare for discs to actually warp. The brake judder that lots of us suffer from is not warping but due to some other reason.

[Cerec1]

I've had my discs pro cut skimmed twice and both times the judder came back eventually. The skim will cure the symptoms but not necessarily what caused them in the first place.

Also we need to get away from this idea of discs 'warping'. I've researched this to death and it is ultra ultra rare for discs to actually warp. The brake judder that lots of us suffer from is not warping but due to some other reason.

So if they don't warp how does skimming get rid of the problem? Even if only short term. Not saying you or your reseach is wrong. Just curious

[MikeFish]

I've had my discs pro cut skimmed twice and both times the judder came back eventually. The skim will cure the symptoms but not necessarily what caused them in the first place.

Also we need to get away from this idea of discs 'warping'. I've researched this to death and it is ultra ultra rare for discs to actually warp. The brake judder that lots of us suffer from is not warping but due to some other reason.

So if they don't warp how does skimming get rid of the problem? Even if only short term. Not saying you or your reseach is wrong. Just curious

In our case the discs generally don't warp. They have a similar feeling to warped discs. The issue is caused by a build up of pad residue on the disc surface thus creating a warp like sensation under braking. It is thought it happens because the brakes are too big for the car and often you don't brake hard enough to clear the residue from the discs which eventually builds up and hardens. Either you need new discs, give the brakes a real good thrashing to warm up and rub the build up off or you can skim the discs which clears the build up (but wont necessarily stop it happening again.If you've ever had warped discs before you will know it's different. In this case you can only feel it with medium pressure on the brakes. If you brake light or heavy they normally feel fine. A warped disc will shake the car to bits and only gets worse the higher the speed you are braking from.

[RS6BRIT]

on this subject, it seems quite clear to me that grooved discs would almost certainly solve this, if not help a great deal. Does anyone know where I could get grooves put on ? I'm thinking of getting phaeton discs, having them grooved an then sticking them on my bell (pun intended!!).

I'm sure that in 99% of cases, it is due to what Mike has said- pad material building up on the disc face due to under use. Grooved discs would IMO solve this.

If anyone knows where I can get grooves added then let me know, or could any engineering Shop do this ? and would they need re balancing if grooves were added ?

[TonyHayers]

It's not disk warp, it's brake pad material build up on the disk.



Actually, er, just what Mike said

[frank]

Ive used the same bloke and so far so good

He didnt drill the backs of the fronts/rears out properly as the drilled holes dont line up on the fronts/rears. (Cant remeber which way round they dont line up)

[adsgreen]

It's not a build up of pad residue that gets cleared - it's more akin to getting even wear. You want the residue on the discs - this is one of the primary reasons brakes are bedded in in order to get an even distribution of pad material.
Brakes stop the car with two methods - one is sheer mechanical gripping of the disc by the pads and the other is at higher temperature where pad material is transferred. This is why brakes feel better when warm as the pad material transfer approach is way better (and less wear and tear on the discs).
However discs have microscopic high and low spots which if you brake lightly only the high spots make decent contact with the pad. The RS4 is overspecc'd on brakes for normal road driving so just contacting these spots is enough to slow the car down. These high spots naturally get hot and enter pad transfer phase where as the low spots don't. This ends up being self fulfilling as the high spots get higher making the problem worse as time goes on.

As such grooved discs won't make much of a difference as they are to deglaze the pads.
The easiest option is to brake harder and more evenly. FWIW, I never cleared out the x-drill holes and none of them were blocked even after 25k on one set of discs. I think this is also related to pushing hard enough to clear the holes.

Given the discs are semi floating (fixed to the bell via spring clips) it would be hard to warp them unless you dramatically overheated them (and I would expect you'd feel brake fade before then).
I'm not a fan of xdrilled - grooved and dimpled are the best I have found.

When I had a car that went through this I found light braking shook the wheel but it got better as the pressure increased.

[manual_daniel]

Although slightly off topic, I want to mention caliper corrosion. This has been mentioned in other threads and I have been advised in past posts to remove the corrosion.

I finally got around to doing the job and I was surprised at how much corrosion there was, more in the lower pad area. It used to be quite difficult to push my car because the pads were not able to move away from the discs. I noticed this one day when trying to push the car and hearing brake noise. When I finally took the pads out there was a lot of corrosion to clear away. Basically, my lower pads were always in contact with the discs. It was very, very difficult to extract the lower pads, I struggled for 20 minutes to get them out. Look at photo number two, that lower plate should be flush with the caliper body but it was pushed up by corrosion by about 3mm causing the pad to jam and not be able to move back and forth. It took a while to clean both calipers out completely but it was well worth it. The car moves far move easily now and rolls on slightly downhills which it did not used to before. After completing the job I took the car to Audi and had new discs and pads fitted, and the car has been fine ever since. The caliper corrosion job has changed the way the brakes feel, and I will be doing it regularly. The only disadvantage is the aluminium is now exposed and will corrode more. So, when I have some time I will remove the calipers and have them refurbished and repainted. I can't recommend this job enough. It was a little overwhelming at first but I followed Sonny's post about brake pad removal and no problems. Thanks Sonny!