Warped brake discs.

paddy

Registered User
Warped discs ? This might help someone with similar problems.

My J hooks are causing problems after 3k miles just like the EBC discs before them and the originals before them.

Had a chat with a guy from Brembo today, I am in the motorcycle trade and have a few contacts and Brembo discs are the same principle on Bikes and cars.

I explained how I had a warped set of discs on the S3 and it was the 3rd set in 25k miles.

Anyway, the point was he said he had never seen a set of warped discs although it was possible in theory for them to warp if they were not correctly stress relieved during manufacture but as its an automated process its unlikely.

What happens apparently is a very small amount of pad material will transfer across to the disc because the disc and pad have a different drag coefficient. it will deposit evenly between the differing surfaces however once the disc has an even coating of the pad material the surfaces are no longer differing, and the material can transfer either way, so you get an uneven surface. This is not visible to the eye and is microns but its enough to alter the breaking friction on the uneven deposits on the disc. This will get worse with heat giving the impression the disc has warped however it is really just like putting a drop of oil on the disc, the pads grip better to the deposits on the disc than to the area with less deposits giving an on off on effect as the disc rotates. The only real cure for this is to get the discs skimmed back to an even surface so the friction is the same all round. This enhances the myth that the discs were warped as skimming them cures the problem.


The problem is pads that work well when cold around town will not be ideal for high performance stopping and pads that work well under great heat will not work well cold round town. The pad material is a compromise not helped by modern carbon ceramic and other high-tech compounds that work well but only under their intended driving conditions.

So you drive around and “commute” for 5k miles with no problem then one day thrash the b*&^^ck out of the thing on the motorway or even a track day and you put a deposit on the disc and your on the slippery slope.

Bottom line is my J hooks look like they are shot simply because its cheaper to fit new than mess about getting them re ground i think.
All this can be avoided i am told with proper bedding in of the pads and discs however there are so many experts out there who have completely different ideas about bedding in it still seems like a guess to me.
I was told to run them in carefully, no sudden braking or prolonged hanging on the brakes. Now i am told to bed them in with half a dozen 60mph to 5mph breaking sessions getting progressively harder and allowing the discs to cool between each session.
What i dont understand is why the brakes an my Transit have done 110k miles on original discs and pads, have to pull up twice the weight from speeds of 5mph to 90mph just like the car and yet the car is a load of hassle ....and why the factory pads and discs did the first 50k miles on the car with no problem yet the Vagbrems and the EBC are trouble ?

Just waiting now for a quote or 3 for skimming to see the next move :)
I am thinking that in the past i have changed discs and pads together, now i am thinking run the discs in with the already settled pads.
Breaks my heart to junk the J hooks so soon as they haven't even worn the paint off ...lol.
 

ch1z64

C'mon you's bhoy's in Green
VCDS Map User
Silver Supporter
@paddy try Brembo disc's and textar pads , only way they might not be any good to you is if your heavy on braking as your car is St2+
 

mechanic69

Registered User
VCDS Map User
Gold Supporter
Warped discs ? This might help someone with similar problems.

My J hooks are causing problems after 3k miles just like the EBC discs before them and the originals before them.

Had a chat with a guy from Brembo today, I am in the motorcycle trade and have a few contacts and Brembo discs are the same principle on Bikes and cars.

I explained how I had a warped set of discs on the S3 and it was the 3rd set in 25k miles.

Anyway, the point was he said he had never seen a set of warped discs although it was possible in theory for them to warp if they were not correctly stress relieved during manufacture but as its an automated process its unlikely.

What happens apparently is a very small amount of pad material will transfer across to the disc because the disc and pad have a different drag coefficient. it will deposit evenly between the differing surfaces however once the disc has an even coating of the pad material the surfaces are no longer differing, and the material can transfer either way, so you get an uneven surface. This is not visible to the eye and is microns but its enough to alter the breaking friction on the uneven deposits on the disc. This will get worse with heat giving the impression the disc has warped however it is really just like putting a drop of oil on the disc, the pads grip better to the deposits on the disc than to the area with less deposits giving an on off on effect as the disc rotates. The only real cure for this is to get the discs skimmed back to an even surface so the friction is the same all round. This enhances the myth that the discs were warped as skimming them cures the problem.


The problem is pads that work well when cold around town will not be ideal for high performance stopping and pads that work well under great heat will not work well cold round town. The pad material is a compromise not helped by modern carbon ceramic and other high-tech compounds that work well but only under their intended driving conditions.

So you drive around and “commute” for 5k miles with no problem then one day thrash the b*&^^ck out of the thing on the motorway or even a track day and you put a deposit on the disc and your on the slippery slope.

Bottom line is my J hooks look like they are shot simply because its cheaper to fit new than mess about getting them re ground i think.
All this can be avoided i am told with proper bedding in of the pads and discs however there are so many experts out there who have completely different ideas about bedding in it still seems like a guess to me.
I was told to run them in carefully, no sudden braking or prolonged hanging on the brakes. Now i am told to bed them in with half a dozen 60mph to 5mph breaking sessions getting progressively harder and allowing the discs to cool between each session.
What i dont understand is why the brakes an my Transit have done 110k miles on original discs and pads, have to pull up twice the weight from speeds of 5mph to 90mph just like the car and yet the car is a load of hassle ....and why the factory pads and discs did the first 50k miles on the car with no problem yet the Vagbrems and the EBC are trouble ?

Just waiting now for a quote or 3 for skimming to see the next move :)
I am thinking that in the past i have changed discs and pads together, now i am thinking run the discs in with the already settled pads.
Breaks my heart to junk the J hooks so soon as they haven't even worn the paint off ...lol.

I had a new set of performance discs and pads, fitted them at home then took it straight around our bypass, really quick and repeated high speed to nothing at each roundabout, only thing was I didn’t allow to cool off, after 15 mins or so the fronts warped badly and it was like one one punching me in the foot when breaking, expensive lesson learnt, the next time was more like normal driving with a few heavy breaking spread apart, seemed to work


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Gazwould

Registered User
Warped discs ? This might help someone with similar problems.

My J hooks are causing problems after 3k miles just like the EBC discs before them and the originals before them.

Had a chat with a guy from Brembo today, I am in the motorcycle trade and have a few contacts and Brembo discs are the same principle on Bikes and cars.

I explained how I had a warped set of discs on the S3 and it was the 3rd set in 25k miles.

Anyway, the point was he said he had never seen a set of warped discs although it was possible in theory for them to warp if they were not correctly stress relieved during manufacture but as its an automated process its unlikely.

What happens apparently is a very small amount of pad material will transfer across to the disc because the disc and pad have a different drag coefficient. it will deposit evenly between the differing surfaces however once the disc has an even coating of the pad material the surfaces are no longer differing, and the material can transfer either way, so you get an uneven surface. This is not visible to the eye and is microns but its enough to alter the breaking friction on the uneven deposits on the disc. This will get worse with heat giving the impression the disc has warped however it is really just like putting a drop of oil on the disc, the pads grip better to the deposits on the disc than to the area with less deposits giving an on off on effect as the disc rotates. The only real cure for this is to get the discs skimmed back to an even surface so the friction is the same all round. This enhances the myth that the discs were warped as skimming them cures the problem.


The problem is pads that work well when cold around town will not be ideal for high performance stopping and pads that work well under great heat will not work well cold round town. The pad material is a compromise not helped by modern carbon ceramic and other high-tech compounds that work well but only under their intended driving conditions.

So you drive around and “commute” for 5k miles with no problem then one day thrash the b*&^^ck out of the thing on the motorway or even a track day and you put a deposit on the disc and your on the slippery slope.

Bottom line is my J hooks look like they are shot simply because its cheaper to fit new than mess about getting them re ground i think.
All this can be avoided i am told with proper bedding in of the pads and discs however there are so many experts out there who have completely different ideas about bedding in it still seems like a guess to me.
I was told to run them in carefully, no sudden braking or prolonged hanging on the brakes. Now i am told to bed them in with half a dozen 60mph to 5mph breaking sessions getting progressively harder and allowing the discs to cool between each session.
What i dont understand is why the brakes an my Transit have done 110k miles on original discs and pads, have to pull up twice the weight from speeds of 5mph to 90mph just like the car and yet the car is a load of hassle ....and why the factory pads and discs did the first 50k miles on the car with no problem yet the Vagbrems and the EBC are trouble ?

Just waiting now for a quote or 3 for skimming to see the next move :)
I am thinking that in the past i have changed discs and pads together, now i am thinking run the discs in with the already settled pads.
Breaks my heart to junk the J hooks so soon as they haven't even worn the paint off ...lol.


Stoptech also agree .

http://www.stoptech.com/technical-support/technical-white-papers/-warped-brake-disc-and-other-myths
 

miltybilty

Registered User
I have hawk hps 5.0 pads on the front of my car with some R1 drilled&slotted, and sometimes they don't make any noise or pulse feeling, but most times they do ....

I assume my brakes also have this diposit issue?

I wonder if there's a way of clearing the deposits off with heavy braking done repeatedly then driven after for awhile with lighter braking ....

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paddy

Registered User
I think unless you changed the pads to some sort of abrasive compound that will clean off the discs then heavy braking will just make the problem worse.
I wondered about wet and drying the disc surface but from what i have read that will make the problem worse over time as the pad material will just stick even harder to the discs.
I am hoping that using the old pads (which are only 3k miles old) that have already bedded in on the re faced discs will help stop this happening again. I will report back ASAP.
 

paddy

Registered User
Update
Discs have gone off to be re faced as this will be cheaper than replacing them.......just.

I think the lesson here is audi spend a lot of time and money getting a disc and pad compound that work together so this does not cause a problem on all their new cars. along comes mr home tuner ( me :) ) and faced with a dozen different discs and even more pads i have to choose a pairing that will work together for my driving/application. Chances are without professional advice i am not going to pick a compatible set at random even though i foresaw this problem and went for VagBrembo discs and Brembo pads. my guess is i chose the wrong pads for the disc compound and my driving but who knows ? I will try the same pads again now they have had loads of heat cycles but its a shot in the dark really.
 

ch1z64

C'mon you's bhoy's in Green
VCDS Map User
Silver Supporter
Have you tried the Textar pad , not much said about them on here but myself an another member have had no probs and they are reasonable priced
 

leshkin

Hold my beer...
VCDS Map User
I still think that your spacers might be causing this. Let us know if this comes back.
 

fernando young

Registered User
i warped two sets of discs after trackdays when i had the stock S3 brakes, so same happened to a couple friend with cupras, which use the same calipers.
tried stock pads, ebc pads, stock rotors and ECS rotors
once i swapped to the RS3 calipers they are remaining straight.

my conclusion is, i think since the S3 calipers have only one big piston, so there is too much pressure is just applied on one spot from one side, making them bend.

any thoughts?
 

paddy

Registered User
I think you are on the right track but i don't think they are bending, the material transfer to the disc will be less over a bigger area as brake pressure will be less also causing less of a concentrated hot spot. So a RS3 Caliper will in effect spread the load better and run a bit cooler.
 

paddy

Registered User
I see vagbrembotechnic do a carrier bracket for the S3 to take Porsche boxter 4 pots. They might work better than the std S3 calipers and are a reasonable price used.
 

fernando young

Registered User
I see vagbrembotechnic do a carrier bracket for the S3 to take Porsche boxter 4 pots. They might work better than the std S3 calipers and are a reasonable price used.
thats the way i went, vagbremtechnic carriers and RS3 calipers. And been tracking the car the same way, and i'm using the same ECS rotors (i rectified them when placing the new calipers) and they are still perfect
 

miltybilty

Registered User
i warped two sets of discs after trackdays when i had the stock S3 brakes, so same happened to a couple friend with cupras, which use the same calipers.
tried stock pads, ebc pads, stock rotors and ECS rotors
once i swapped to the RS3 calipers they are remaining straight.

my conclusion is, i think since the S3 calipers have only one big piston, so there is too much pressure is just applied on one spot from one side, making them bend.

any thoughts?
Hmmmm the single piston sliding caliper style brake could be causing issues like you suggested ....

Now when I was swapping my springs I noticed that the piston side of the rotor had a bigger lip meaning that it's worn more on that side .... Guess I may swap to boxster calipers soon.

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paddy

Registered User
Well an update....
The engineering shop re faced the discs and having refitted them the garage is not happy with the run out again so looks like the discs are shot now. I can't be ***** to take this up with Vagbrembotechnik , i have no idea who they are anyway ? Certainly nothing to to do with VAG or Brembo as far as i can see.
I have opted for a std set of S3 audi discs and pads, they work fine anyway and you have some come back with OEM parts that you don't get with after market stuff..A very expensive lesson learned here. Stupid thing is i am a Brembo supplier myself but for motorcycle stuff and its a different importer and agent to car stuff. And i never recommend anything other than OEM for Brembo equipped bikes.......then i go and buy some Vagbrembotechnik tat for my car...lol :)
 

miltybilty

Registered User
Vagbremtechnic .... Not brembo ....

I think vagbremtechnic is a completely different brand to brembo brakes .... I think brembos rotors would be way better ....

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paddy

Registered User
Agree but the idea is to fool people into thinking Vagbrem is to do with either VAG or BREM bo....its only when i looked up recommended pads and found Vagbrem dont list VAG or Brembo pads i realised this is a completely different company , maybe its just me slow on the uptake but i would never had bought their discs had i realised. :)
 

miltybilty

Registered User
Agree but the idea is to fool people into thinking Vagbrem is to do with either VAG or BREM bo....its only when i looked up recommended pads and found Vagbrem dont list VAG or Brembo pads i realised this is a completely different company , maybe its just me slow on the uptake but i would never had bought their discs had i realised. :)
Yes I agree .... Seems like it is made to truck people into think it's part vag or brembo ....

I think there good for other parts ....

Maybe try stoptech with cryo treatment .... There supposed to be more reliable.

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paddy

Registered User
I have ordered stock S3 discs and pads now. Bottom line is for road use they will fire off the ABS quite easily and there is not much more a brake system can do ? I would agree on the track, brake fade and wear will be a more important consideration but not many people will push brakes past 100mph on the public roads and that's only 2/3 of their std design working parameters.
 

paddy

Registered User
Just an update to wrap this thread up

The vagbremtechnik discs were skimmed and re fitted to the car. Put car on the brake test rollers and even on there you could see them grabbing and releasing as they turned. Took discs off again and fitted new genuine discs and pads, took for extended road test and now perfect.
The skimmed discs were still running withing tolerance so i can only assume there was a casting problem here that was right through the cast iron as it didn't clean up with skimming. bottom line is i am £1k out of pocket with labour and new parts. Lesson learned with after market parts :).
 

Daveyonthemove

Well-Known Member
VCDS Map User
Sounds like an expensive experiment, thanks for sharing so others can avoid making the same mistake.
I've been looking for discs and pads for the rear of my S3 and finally settled on Brembo discs and pads from ECP.
They have a big sale on right now, so I managed to get all of it for under £97 where usually one discs is £73 each.

They will be getting fitted in the near future, but no rush as current stuff is OK, but needs changing for the MOT in November to ensure no advisories.
 

paddy

Registered User
driving along to day hit the brakes from rather high speed and the vibration through the car was enough to push the pads back in the calipers. Had a couple of gentle attempts to slow it down as shaking was so bad, once back at sensible speeds its fine again and i could brake hard..
4th set of discs so its not them. its not wheel bearings either. I think i give up. 2 specialist garages have given up already. its had full strip down, new drop links and so on but i get about 3k miles from a set of discs. 2 sets of Audi std s3 discs, one set of EBC and 1 set of vagbrem j hooks but its not discs.
 

miltybilty

Registered User
driving along to day hit the brakes from rather high speed and the vibration through the car was enough to push the pads back in the calipers. Had a couple of gentle attempts to slow it down as shaking was so bad, once back at sensible speeds its fine again and i could brake hard..
4th set of discs so its not them. its not wheel bearings either. I think i give up. 2 specialist garages have given up already. its had full strip down, new drop links and so on but i get about 3k miles from a set of discs. 2 sets of Audi std s3 discs, one set of EBC and 1 set of vagbrem j hooks but its not discs.
What pads you running?

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paddy

Registered User
Tried EBC, Genuine Brembo and currently Audi original std.
 

samuelh_888

Registered User
@paddy - time to take the spacers off or try a different set. Even as part of the elimination process...
 

paddy

Registered User
Agree Sam its defo fronts so will take spacers off tomorrow.
 

paddy

Registered User
That said this started at 48k miles, before it was tuned or had spacers, its now on 78k miles and has had diferent tyres, wheels swapped front back, new wheel bearings, drop links, front springs, discs pads, and so on.
 

miltybilty

Registered User
I had warped brake feel in my fronts for a couple months or so .... Eventually went away .... It's like I ground the deposits off after awhile.

Who installed your wheel bearings?

Also spacers .... What brand?

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downtothebone

Registered User
I’ve had bad wheel shake since I had the Forge big brake kit fitted. Also had H&R 8mm spacers fitted to get clearance. Decided to swap the spacers out for APR 10mm with the lip. Shake completely gone - couldn’t believe it. I had lived with this for years. The shake was really bad at about 70ish.
I’m going to have a close look at the old spacers to see if I can spot any obvious defects. Only other thing I did was used a wire brush to clean the back of the wheel and the hub.
I had no shake when actually braking so slightly different scenario ...
 

paddy

Registered User
My spacer are H&R hubcentric 10mm.
Because it only does it from braking at 100mph plus i will remove the spacers and also try going up on tyre pressures a bit
What are people running with std S3 225/40 18" wheels ?
 

kcpism

Registered User
I’m going to have a close look at the old spacers to see if I can spot any obvious defects. Only other thing I did was used a wire brush to clean the back of the wheel and the hub.
I had no shake when actually braking so slightly different scenario ...

@downtothebone Would you like me to test them for you? :icon thumright:
 

paddy

Registered User
Pretty sure there is no difference between APR and H&R hubcentric ?

I think its more technical than this for example if you fit spacers you will alter the camber on the wheel. i just swapped the wheels front to back and its 10x worse despite the guy overriding the balance machine to get the balance down to +/- 1g the wheels are the same and the tyres are the same make and age.
 

samuelh_888

Registered User
@paddy -225/40/18 on standard alloys I didn’t run spacers - there’s no need unless you have a big brake kit. Yeah I get asthetics but...
 

paddy

Registered User
Will try again today without the spacers , fingers crossed.
 

stbuk

Registered User
Just want to throw out there that I run the vagbrem j hooks on standard callipers, came back from 20 odd laps of the ring a few weeks ago + 10,000 miles of them on the car and I only get noise that’s expected from hooked/slotted discs. No vibrations.

Nuespeed wheels, no spacers.

I ran standard wheels on 12mm H&R hub centric before the neuspeed and had no issues either.

Not something daft like knackered top mounts that you’re only seeing under heavy breaking? I had vibrations that was a split bearing on the top mounts.
 

leshkin

Hold my beer...
VCDS Map User
As I mentioned before paddy, if spacers do not resolve it, give Marcus (http://www.discskimmers.com/) a shout and he absolutely will get to the bottom of the issue. I'd put my own money on it.

Runoff issues are never isolated once they start happening, as the disk deformation is a simptom not the cause and prolonged runoff issues can cause the wheel mounting surface and the hub to deform due to uneven heat dissipation over many heat cycles. The fix is simple, but takes experience and skill to properly level them.
 
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paddy

Registered User
OK chaps here is the definitive results :)
We have a 4 mile straight stretch of empty duel carriage way near me , built in the days when councils had money but it doesnt really go anywhere :)
First run without spacers, accelerate up to 90 smoothly, no sign of wobble.
back of and let the speed drop off without brakes, starts to wobble at 80, hold 80 wobble gets worse.
Brake for the roundabout wobble on brakes at 80 smooths out below 60
Second run, now wobbles all the way from 70 up to 90
Hit brakes and its bordering on a tank slapper :), wobble is pushing pads back but as speed drops below 60 it just a normal ( well normal for this car) judder on the brakes through the steering wheel.
Third run now juddering on brakes at all speeds, wobble on steering just at 80+
Fourth run Much better now steering feels like its rattling but brake wobble nearly gone.


conclusion........
the wobble on speed and brakes is linked, its not wheel balance and its not discs it just manifests itself as an out of balance or warped disc symptom vvia the steering wheel and brakes. Drive normally below 60mph and its as good as gold.

****** off, come home, vow to lay car up and use the van :-( simply cant afford to waste any more money on it, garages not interested as they cant test the fault as will not go over 65mph in a customers car apparently for insurance reasons. Think i might have a little cry :)
 

miltybilty

Registered User
OK chaps here is the definitive results :)
We have a 4 mile straight stretch of empty duel carriage way near me , built in the days when councils had money but it doesnt really go anywhere :)
First run without spacers, accelerate up to 90 smoothly, no sign of wobble.
back of and let the speed drop off without brakes, starts to wobble at 80, hold 80 wobble gets worse.
Brake for the roundabout wobble on brakes at 80 smooths out below 60
Second run, now wobbles all the way from 70 up to 90
Hit brakes and its bordering on a tank slapper :), wobble is pushing pads back but as speed drops below 60 it just a normal ( well normal for this car) judder on the brakes through the steering wheel.
Third run now juddering on brakes at all speeds, wobble on steering just at 80+
Fourth run Much better now steering feels like its rattling but brake wobble nearly gone.


conclusion........
the wobble on speed and brakes is linked, its not wheel balance and its not discs it just manifests itself as an out of balance or warped disc symptom vvia the steering wheel and brakes. Drive normally below 60mph and its as good as gold.

****** off, come home, vow to lay car up and use the van :-( simply cant afford to waste any more money on it, garages not interested as they cant test the fault as will not go over 65mph in a customers car apparently for insurance reasons. Think i might have a little cry :)
Never, never give up/in!

Anyway .... Try swapping rims with someone .... Could be something up with them.

And it also could be an ABS issue ....

Are all your steering components new?
You could test them with a friend for looseness .....

How old are the calipers? Any seizing?
If one had a sticking problem, it could heat up the pad and rotor causing complications.

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paddy

Registered User
I think stbuk is closest so far with suspension , poss top mounts so thats the next thing i think. Maybe a bush in the steering but today i noticed a slight clonk when i stop pointing down hill then reverse back up hill.............could this be a clue at last :)
 
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