Warped disks or something else

[gingerxela]

Hi all
Lots of threads on this forum about disk problems, but thought i would ask as there is lots of RS4 B8 knowledge here. I purchased an RS4 back in Oct 2018 with 29,000 on the clock and it had just had new Audi OEM front disks fitted. 3,000 miles later i get what feels like warped front disks that you can feel braking from 40 mph and if you brake from 80 mph feels like it will shake your fillings out. Dealer agrees to investigate, another set of new OEM front disks fitted all covered under warranty, happy owner again. Then last week 2,000 miles later i can already start to feel it developing again and am about to contact the dealer as its still under warranty. I cannot believe the car can get thru 3 sets of front disks in 5,000 miles. The car is not being thrashed, just normal spirited RS4 road use. It has Audi OEM disks and pads fitted

Any ideas

ginger

[Thundercliffe81]

Hi all
Lots of threads on this forum about disk problems, but thought i would ask as there is lots of RS4 B8 knowledge here. I purchased an RS4 back in Oct 2018 with 29,000 on the clock and it had just had new Audi OEM front disks fitted. 3,000 miles later i get what feels like warped front disks that you can feel braking from 40 mph and if you brake from 80 mph feels like it will shake your fillings out. Dealer agrees to investigate, another set of new OEM front disks fitted all covered under warranty, happy owner again. Then last week 2,000 miles later i can already start to feel it developing again and am about to contact the dealer as its still under warranty. I cannot believe the car can get thru 3 sets of front disks in 5,000 miles. The car is not being thrashed, just normal spirited RS4 road use. It has Audi OEM disks and pads fitted

Any ideas

ginger

Hiya mate.

Hmmmmm. I've had issues with warped discs and had to replace myself. Long story. But Audi are compensating me and we're sorting some other issues. I know how ya feel. It's very unnerving. I agree, unless you're thrashing it, I find it hard to believe it can warp 3 sets. Only thing I can think of is a serious alignment issue or hub bearing/wheel hub off centre or something. Is it both front discs or was it a different side each time? Did Audi take disc measurements to determine it was disc warping?

I'm not that technically minded. Only what I've learned on here and through coming to love the cars beautiful flaws haha.

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[Covkiller]

Disks do not warp, it's something else. There are plenty of recent threads about this.

[Surrey Sam]

How do the wheels get cleaned? I have an unproven theory.

[noidea]

How do the wheels get cleaned? I have an unproven theory.

I am interested in your theory Sam?

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[Thundercliffe81]

How do the wheels get cleaned? I have an unproven theory.

I am interested in your theory Sam?

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Same. I think I know what he's saying

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[Surrey Sam]

I'm speculating that aggressive cleaning chemicals can cause corrosion between the friction ring and the bell expansion pins, this would stop the disc from floating and working as it should.

A saline solution could do the same, so road salt and water during winter times.

[Thundercliffe81]

I'm speculating that aggressive cleaning chemicals can cause corrosion between the friction ring and the bell expansion pins, this would stop the disc from floating and working as it should.

Yeah I'd thought this when I used the brake cleaner haha. Obviously that was a different story. But they did not look good!

Do you think it's limited to high PH acidic cleaners? Gyeon fallout is PH Nuetral and is bloody good at what it does. But with this in mind, and having had serious issues with brakes as you know (now replaced and are awesome) I might just apply a lot more carefully now. Avoiding calliper and discs. Thoughts?

The good old polish £5 job would be a strict no for countless reasons but even things like Carplan demon spray are ruthless and readily available from Halfords.

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[Surrey Sam]

Yes, I'm thinking both acidic and alkaline chemicals could cause it. I'm not too informed on the fallout removers other than in base form, they're a strong acidic chemical (Sodium Thioglycolate), does the reaction with iron shift PH? Or does the solution when in contact with too much iron for it to deal with, burnout and oxidise the surface characteristics more at a microscopic level. All I know is that over the last year I've been far more careful with chemicals being sprayed onto the discs and drying them off after washing. This has limited by warping issues which I had huge problems with on the previous generation B7 RS4 and to begin with on the B8.

[Thundercliffe81]

Yes, I'm thinking both acidic and alkaline chemicals could cause it. I'm not too informed on the fallout removers other than in base form, they're a strong acidic chemical (Sodium Thioglycolate), does the reaction with iron shift PH? Or does the solution when in contact with too much iron for it to deal with, burnout and oxidise the surface characteristics more at a microscopic level. All I know is that over the last year I've been far more careful with chemicals being sprayed onto the discs and drying them off after washing. This has limited by warping issues which I had huge problems with on the previous generation B7 RS4 and to begin with on the B8.

Really good advice that. Its certainly a variable worth eliminating! I'm gonna start drying my discs now.

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[johnnydog]

Hi all
Lots of threads on this forum about disk problems, but thought i would ask as there is lots of RS4 B8 knowledge here. I purchased an RS4 back in Oct 2018 with 29,000 on the clock and it had just had new Audi OEM front disks fitted. 3,000 miles later i get what feels like warped front disks that you can feel braking from 40 mph and if you brake from 80 mph feels like it will shake your fillings out. Dealer agrees to investigate, another set of new OEM front disks fitted all covered under warranty, happy owner again. Then last week 2,000 miles later i can already start to feel it developing again and am about to contact the dealer as its still under warranty. I cannot believe the car can get thru 3 sets of front disks in 5,000 miles. The car is not being thrashed, just normal spirited RS4 road use. It has Audi OEM disks and pads fitted

Any ideas

ginger

I had exactly the same scenario with my B7. If you search the B7 forum you should find all the info you need to progress your issue further. From memory it was around 2010 - myself and Stu on that forum got satisfactory results under Audi warranty in the end, although my issues started whilst the car was still in its 3 year manufacturers warranty.
It is correct that, theoretically, there is no such thing as a warpped disc - it is usually a build up of transferred pad material when the pads are clamped to a hot disc, for example when holding your foot on the brake whilst stationary. There are sites based in the US with plenty of information about the issue of brake pad material transfer onto hot discs which caused high spots and the resultant judder which is mistakenly diagnosed as warped discs.
Incidentally, with my B7, it involved 2 sets of front discs and pads, one set of rear discs and pads, replacement front and rear hubs and new front calipers - none of which cured the problem. In each instance of replacement discs, the recommended Audi bedding in procedure was carried out which was a couple of hours time and 80 plus miles of rigidly sticking to their procedure.
Whether Audi will look on your issue as favourably as they did back in 2010, is questionable, especially if you don't have an Audi extended warranty, with all B8's now being over 3 years old. If you purchased it ftom an Audi deslership, then you should have a 12 month used car warranty which may help you to resolve the issue, although a used car dealership warranty is not the same as a new car 3 year warranty.
If you struggle to find the topics, I may be able to point you in the right direction.

[Thundercliffe81]

Hi all
Lots of threads on this forum about disk problems, but thought i would ask as there is lots of RS4 B8 knowledge here. I purchased an RS4 back in Oct 2018 with 29,000 on the clock and it had just had new Audi OEM front disks fitted. 3,000 miles later i get what feels like warped front disks that you can feel braking from 40 mph and if you brake from 80 mph feels like it will shake your fillings out. Dealer agrees to investigate, another set of new OEM front disks fitted all covered under warranty, happy owner again. Then last week 2,000 miles later i can already start to feel it developing again and am about to contact the dealer as its still under warranty. I cannot believe the car can get thru 3 sets of front disks in 5,000 miles. The car is not being thrashed, just normal spirited RS4 road use. It has Audi OEM disks and pads fitted

Any ideas

ginger

I had exactly the same scenario with my B7. If you search the B7 forum you should find all the info you need to progress your issue further. From memory it was around 2010 - myself and Stu on that forum got satisfactory results under Audi warranty in the end, although my issues started whilst the car was still in its 3 year manufacturers warranty.
It is correct that, theoretically, there is no such thing as a warpped disc - it is usually a build up of transferred pad material when the pads are clamped to a hot disc, for example when holding your foot on the brake whilst stationary. There are sites based in the US with plenty of information about the issue of brake pad material transfer onto hot discs which caused high spots and the resultant judder which is mistakenly diagnosed as warped discs.
Incidentally, with my B7, it involved 2 sets of front discs and pads, one set of rear discs and pads, replacement front and rear hubs and new front calipers - none of which cured the problem. In each instance of replacement discs, the recommended Audi bedding in procedure was carried out which was a couple of hours time and 80 plus miles of rigidly sticking to their procedure.
Whether Audi will look on your issue as favourably as they did back in 2010, is questionable, especially if you don't have an Audi extended warranty, with all B8's now being over 3 years old. If you purchased it ftom an Audi deslership, then you should have a 12 month used car warranty which may help you to resolve the issue, although a used car dealership warranty is not the same as a new car 3 year warranty.
If you struggle to find the topics, I may be able to point you in the right direction.

This is really good to know. I learned a lot from reading several us posts on this. To do with B7 mainly but all cars basically. At the lights, I've stopped using the hill hold assist. Although out of habit, I'm keeping my foot on the brakes. I'm trying to get into routine of putting the car into park.

Its a clunky (less smooth) procedure to pull away. Using a dual clutch haha. But do you think that would eliminate the heat and pad transfer? My brakes are doing great now since the change and I'm pushing on harder and harder gradually. The squeel has gone and I see good transfer layers across the discs. But when I do finally go balls out again, I'm going to have to remember to put it into park at junctions etc. Its not ideal but this was such an unexpected expense for me. Full brake replacement. Long story with Audi but they're sorting it now retrospectively.

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[Surrey Sam]

With respect, I disagree with the pad transfer aspect. Squeaky brakes yes but wobble no.

[johnnydog]

With respect, I disagree with the pad transfer aspect. Squeaky brakes yes but wobble no.

To quote from an Audi TPI bulletin for the B7, which I can only presume is similar to the B8, it states the following-
'Audi RS4 steel brake discs have a perfectly symmetrical design and a manufacturing tolerance of three hundreds of a millimetre, therefore warping as a result of excessive heat is next to impossible. The exception to this is in rare cases when the vehicle has been parked or left standing immediately after a period of severe braking or track use. This holds heat in this area while the rest of the brake disc surface cools down uniformly'.
It then goes through an elimination fault check list .

I don't know whether you are familiar with the above mentioned Audi bedding in procedure Sam, but it is a very intense operation quoted as being for 'sportier driving' as follows -

It involves driving to 100 kmph, then braking as you would 'comfortably on the approach to traffic lights', reducing the speed to about 20kmph before accelerating back to 80 kmph. It outlines the importance of not coming to a complete stop. The vehicle has to be then driven for 1 minute at 80 kmph for the brakes to cool before the braking operation is carried out again. This is done 50 times. There is then a period of driving for the brakes to cool down. It is then followed by five 'full' brake applications from 100 kmph down to a complete stop avoiding activating the ABS, and immediately accelerating at 'full power' back to 100 kmph before repeating the operation four more times. It concludes that the brakes are now at a temperature (very hot) that the pads will emit gas to obtain optimal coefficients.
It states that on no account should the vehicle be parked in this state, but the next stage is brake cleaning. When the brake pads emit gas, they leave a film of dirt and lining material on the brake disc. The brakes must be allowed to cool by driving at 80 kmph for 10 minutes without stopping. Then three full braking operations from 100 kmph to a complete stop must be carried out with a cooling off period of driving at 80 kmph for approximately 3 minutes between them.
It then concludes the brakes are now bedded in for 'sportier' driving. The nature of the procedure makes the choice of road to carry out this procedure quite difficult.
There must be a strong argument for not coming to a complete standstill for more than a couple seconds with hot brakes from the above procedure. The subsequent pad deposits transferred to a hot disc are extremely hard and in the worse cases, cannot be removed from the disc face except by machining. Once the build up starts, the pad material transfered creates a 'high spot'' which compounds with further use, until it gets to a point where it is felt through the brake pedal. There is an argument that regular firm braking does a lot to alleviate this issue, as outlined in the 'cleaning procedure', where any minor build of pad material in one spot on the disc is removed by firm braking before it builds up to a high spot causing the kicking through the brake pedal.

As this procedure is very time and labour intensive, and ideally needs two technicians (one to drive and one to ensure the exact procedure is followed and to complete the check sheet!), I find it hard to accept that Audi dealerships will pay the cost of two technicians the time to complete it (2 hours) plus fuel, and so I suspect that this bedding procedure isn't carried out to the letter in most cases.

So there you have it......

[gingerxela]

Guys
Latest update is the the garage i purchased the car from changed the front hubs and bearings and the fault was still there. At this point the car went to AUDI main dealer who has now changed all 4 disks and pads and now warrantee the repair. I've so far done 500 miles since getting it back at if it comes back it will be in another 1500 ish miles. It now means the car is on its 3rd set of new front disks in 5000 miles. I'm starting to believe the fault was not actually the front disks, but the back ones and somehow the fault was interfering with the ABS sensors and partially triggering the ABS even at relatively low speeds. The AUDI main dealer has never seen the fault before and therefore changed all 4 disks and pads and the bill was picked up by the garage i bought it from. I will keep you posted if the fault comes back
Ginger