Brake judder...due to warped discs?

cyhliu

cyhliu

Active Member
It's my birthday
Joined
Jun 4, 2014
Messages
161
Reaction score
57
Points
28
Location
London
I had a long drive this weekend and noticed that when braking hard, I get a lot of judder, so much that the whole car vibrates with it.

I had the MOT and servicing done in June and at both times they said my brakes are fine and still had life in them. Could it be warped discs that is causing this? It's never happened to me before so I'm not sure if it could be due to this or something else.

If so, how will I know which one is warped, I don't fancy changing all discs to find out (as that would be a costly exercise!). Thanks.
 
Chances are what you will have is pad transfer onto the discs.

Try taking them through a heat cycle to clean them up and see if they improve.
 
It would depend on, how much car vibrates at certain speeds, I guess?
As that shouldn’t be much important, I would replace both front discs, at least.

They can warp due to sudden temperature change.
After a nice drive you decide to go to car wash. They spray your hot wheels and brakes with acid cleaning solution and thats it.
Discs get a thermal shock an warp.


Sent from my iPhone using Tapatalk
 
Not just because of warped discs, since you can get judder from bad bushings and joints in the suspension set up aswell.
 
What you describe sounds like possible warped discs. Useful video - suggesting that only warped front discs cause the steering to shake. The only way to accurately measure the "run out" i.e. warping, is with a special tool as shown. Simple visual inspection cannot prove whether or not a disc is warped. Unless you are creating excessive heat with braking (or a seized brake caliper) warping usually occurs when the disc is older, worn and close to, or below, its minimum thickness specification.

 
I have no idea how true this is but I have read from a fair few places that brake discs rarely warp, more often things such as pad transfer etc.

In any case, Marcus from http://www.discskimmers.com/ comes highly recommended for diagnosing and fixing brake judder, and he can skim on the hub if it comes to that. Have a chat to him though, he’ll help as much as possible before just saying you need to skim.


Sent from my iPhone using Tapatalk
 
Yep I've read these internet articles which usually originate from "brake experts" in the US who insist that brake discs (rotors) never warp. :rapture: They allege that brake juddering is caused instead by an invisible film of brake pad material (which even causes the discs to have measureable, out-of-tolerance run out :highly amused:) which gets deposited on the metal surface. They say the problem is instead caused by drivers not "braking properly" and not following some elaborate "bedding in" process :smile new:. So they would have us believe that after years of trouble free motoring the OP's discs are still in perfect condition and that the problem is really that he/she has just started "braking incorrectly" which has caused pad material to stick to the discs :haha:
 
Brake Discs skimming, roughly 35 years ago Ford main dealers used to hold one of these lathes when quite a lot of Fords suffered from this, they also held a "mounted wheel balancing" bit of kit as well. I'm very very surprised that there are not more operators of this sort of kit around the country now a days, maybe better front suspension and brake designs have got rid of a lot of issues, also if and when it is just a warped or rusted discs, skimming only really works price wise on cars with expensive discs, for the majority it is new discs - old ones into recycling bin!
 
rum4mo said:
Brake Discs skimming, roughly 35 years ago Ford main dealers used to hold one of these lathes when quite a lot of Fords suffered from this, they also held a "mounted wheel balancing" bit of kit as well. I'm very very surprised that there are not more operators of this sort of kit around the country now a days, maybe better front suspension and brake designs have got rid of a lot of issues, also if and when it is just a warped or rusted discs, skimming only really works price wise on cars with expensive discs, for the majority it is new discs - old ones into recycling bin!
Click to expand...

Wish I could have a mounted wheel balance. I’ve got a juddering problem at certain speeds and also on braking and no ****** seems to be able to solve it. I’ve had my wheels balanced 3 times by 3 places, all said they were not balanced when I got there - who the hell do I believe?! Wish I could do it myself tbh


Sent from my iPhone using Tapatalk
 
Thanks for the comments, thought I'd give a quick update.

I tried to take them through a heat cycle on my trip back home at Christmas but it hadn't really made much of a difference (thanks @RyanJonS4). I then called a couple of garages (these were Audi dealers) and they were quoting me £150 just to diagnose what could be the problem (even though the website says its £60!).

So I dropped Marcus an email asking for a quote for a mobile service, but sadly he's stopped offering that service. Called him a couple of days ago and have arranged to take my car to his workshop next weekend. He is very knowledgeable and asked some questions that I hadn't even thought of but he thinks it's to do with my alloys as I had purchased a set of refurbished S5 alloys. He's going to have a look and fingers crossed it'll be resolved in a week! (thanks @meph137). Will keep you posted.
 
Most garages, even Audi I suspect will simply fit new pads and discs if a customer complains of brake shudder, and not actually investigate the cause. That might be a little harsh.

I've read about pad transfer too, but haven't experienced it myself. Used to have an old Audi 80 Avant that ate brakes for breakfast which I simply deduced as insufficient disc ventilation and cooling. It had solid front disks, so heat spots and brake vibration weren't uncommon given it was a heavy car.

First off, there are a couple of things you can do before checking your car into a garage.

Drive the car from cold for a good few miles and coast to stop without braking. Now touch the discs. They may be slightly warm, but if in doubt touch the alloy first. If they're hot, then chances are it's a sticky caliper piston, possibly because the dust sleeve is damaged allowing the piston surface to corrode, or the slider pins are siezed, again because they need lubricated. The sliders can be replaced or even salvaged with little fine grade wire wool and lubricated. If there's any pitting or severe corrosion, then replacement is the only course of action. Similarly with the piston bore. Audi still do exchange caliper service. If you're rebuilding the caliper Bigg Red is a good business to deal with. Piston should be lubed with a little Lockheed red grease before compressing back into caliper. I'd also renew the brake fluid which may be exacerbating the problem as it absorbs moisture. Audi recommend renewal every 2 years.

Is it suspension related or tyre related? Tyres and wheels are easily checked, so a flat spot can give symptoms of vibration at speed, as can a thrown wheel balance weight.

Suspension wise, then the best you can do is jack up and hold wheel at 10 to 2 position. Rock from side to side paying special attention to upper control arms. Any movement at pinch bolt and a definite clunk will indicate arms are worn which certainly isn't helping things. Tie-rod ends and lower suspension arms are also contenders, as are ARB links. All will exaggerate vibration under braking.
 
This is a common problem with the B8/B8.5 S4 when driven hard due to insufficient disc ventilation and the lack cooling. There are no brake cooling ducts from the front of the car such as those often found on BMW's etc.
Do the brakes judder all the time or only when driven hard? If only when driven hard then changing the discs won't solve the problem and the next set will probably do the same.
Switching to a larger big brake setup with thicker two peice/floating discs preferably with some brake cooling and DOT5 fluid is the way forward. Look at what cars such as the R8, S8 and RS models have standard, even the newer B9 S4 has got uprated brakes over the B8/B8.5 with Brembo calipers.
 
I’m pleased to report no more judder for me! Turns out it was the caliper which wasn’t seized just ‘lazy’ at returning. This eventually was overheating pads and discs leading to judder.

The pads and discs were new so i haven’t replaced them and there is no more judder!

Very pleased
 
Going through this thread, I think might have similar problem.

When approaching traffic lights and slowly braking, car seems to pulse. Only when pressing brake pedal. It like I would deliberately pulsing on the brake pedal.

When braking from faster speed, it is noticeable as slight vibrations.
All this can be felt at the back of the car. No vibrations on the steering wheel.

I have solid brake discs at the rear and had all 4 corners replaced late 2016. There is a hair thickness lip on both brakes from wear so plenty of life left.

I recently changed alloys for the aftermarket ones. Thought this might be the problem now.
Reading about insufficient brake cooling thought, wheels could not allow as much air cooler air through as oem ones.

I did however, painted the callipers not so long before new wheels been slapped on.
I did masked all as best as I could but maybe missed something?
All rubber pars were covered and I made sure, they are not painted.

How can I find out if there is a sticky pad somewhere or lazy piston?

Also, last year service I had, carried out brake fluid change. Could there be a trapped bubble inline?

My car is heavier: A6 C6 2010 Avant so might heat up discs faster.


Sent from my iPhone using Tapatalk
 
I tested mine by lifting the car on all four sides do a brake fluid change and then spinning the discs. One was noticeably more resistant than the other even though the piston would eventually retract.

I also had a laser temperature monitor which showed disc on one side was about 70degC warmer than other side
 
Gents, just got back from visiting Marcus at his garage and I'm pleased to say he's solved the brake judder issue.

There was a couple of issues, one of which was due to my alloys not sitting flat to the hub, the front nearside alloy was the worse of the four. Although the alloys had been refurbed professionally (so I was told) it looks like the hub mount plate had not been cleaned and did not sit flat to the hub.

The second issue, which Marcus thinks the main culprit was the fitting of the brake discs themselves. Marcus wanted to take them off to have a look at them and when he tried, we found out they were seized by rust and needed a few blows of a hammer before they would come off. Looks like when they were fitted, the fitters hadn't bothered cleaning and copper greasing the hubs so rust had just eaten away at the disc and caused them to be misaligned. Marcus cleaned them and refitted them before skimming. Apparently mine were one of the worse he's seen, which isn't probably an accolade to have achieved! Once skimmed and alloys fitted, I was told to take it on the nearby bypass and carry out 6 heat cycles to bed the pads in to the discs and now the brakes work perfectly.

So what we both was expecting to be a quick, front two discs to be skimmed turned out to be a long 3 hour, four disc skim and two front disc removal and refit job! Marcus said he's probably only going to continue with the disc skimming for another year as he has a new business he's working on, shame as we need people like Marcus who is knowledgeable and friendly and enjoys what he's doing.

@KrisKrk Marcus mentioned that the pedal pulsing usually means issues with the front discs so I'm not sure what it means when its your back end is vibrating(!). May be give him a call.
 
cyhliu said:
Gents, just got back from visiting Marcus at his garage and I'm pleased to say he's solved the brake judder issue.

There was a couple of issues, one of which was due to my alloys not sitting flat to the hub, the front nearside alloy was the worse of the four. Although the alloys had been refurbed professionally (so I was told) it looks like the hub mount plate had not been cleaned and did not sit flat to the hub.

The second issue, which Marcus thinks the main culprit was the fitting of the brake discs themselves. Marcus wanted to take them off to have a look at them and when he tried, we found out they were seized by rust and needed a few blows of a hammer before they would come off. Looks like when they were fitted, the fitters hadn't bothered cleaning and copper greasing the hubs so rust had just eaten away at the disc and caused them to be misaligned. Marcus cleaned them and refitted them before skimming. Apparently mine were one of the worse he's seen, which isn't probably an accolade to have achieved! Once skimmed and alloys fitted, I was told to take it on the nearby bypass and carry out 6 heat cycles to bed the pads in to the discs and now the brakes work perfectly.

So what we both was expecting to be a quick, front two discs to be skimmed turned out to be a long 3 hour, four disc skim and two front disc removal and refit job! Marcus said he's probably only going to continue with the disc skimming for another year as he has a new business he's working on, shame as we need people like Marcus who is knowledgeable and friendly and enjoys what he's doing.

@KrisKrk Marcus mentioned that the pedal pulsing usually means issues with the front discs so I'm not sure what it means when its your back end is vibrating(!). May be give him a call.
Click to expand...

Thank you for asking Marcus regarding my issue.

It’s definitely not the air bubble then. I have good brake pedal travel and nor resistance or pulsing there.
It only seems like it, when you slowly coasting to stop and applying brakes gently. And only in the rear, I think. Nothing on the steering wheel.

Might need to find someone with laser thermometer and do few test runs.

Will get the wheels balanced again anyway.

Glad it all worked well for you.

Sorry for asking but who is this Marcus.
A mechanic or brake specialist? Where is he based?


Sent from my iPhone using Tapatalk
 
Drilled disks can cause this problem after long hard driving.
 
KrisKrk said:
Going through this thread, I think might have similar problem.

When approaching traffic lights and slowly braking, car seems to pulse. Only when pressing brake pedal. It like I would deliberately pulsing on the brake pedal.

When braking from faster speed, it is noticeable as slight vibrations.
All this can be felt at the back of the car. No vibrations on the steering wheel.

I have solid brake discs at the rear and had all 4 corners replaced late 2016. There is a hair thickness lip on both brakes from wear so plenty of life left.

I recently changed alloys for the aftermarket ones. Thought this might be the problem now.
Reading about insufficient brake cooling thought, wheels could not allow as much air cooler air through as oem ones.

I did however, painted the callipers not so long before new wheels been slapped on.
I did masked all as best as I could but maybe missed something?
All rubber pars were covered and I made sure, they are not painted.

How can I find out if there is a sticky pad somewhere or lazy piston?

Also, last year service I had, carried out brake fluid change. Could there be a trapped bubble inline?

My car is heavier: A6 C6 2010 Avant so might heat up discs faster.


Sent from my iPhone using Tapatalk
Click to expand...

KeisKrk, Did you ever get to the bottom of your issue? I have exactly these same symptoms on my A6 Allroad (2007). I'm not certain if coming from back though in my case. I replaced front disks and pads about 6 months ago and they are still like new. The rear disks/pads are older. I spotted on front when I inspected that track rod end had play, so replaced this but the symptoms remain. Didn't find any other ball joints with issues. Thinking I might replace rear disks/pads and inspect callipers at the same time in case they are not releasing cleanly. Would be good to hear from you if you sorted it. Cheers,m Paul
 
  • Like
Reactions: KrisKrk
Hey,
It kinda resolved.
Been to the garage to have the wheels rebalanced and rear offside wheel was off balance by 25/10grams and nearside by 10/10grams.
Front offside was fine but nearside was off again by 10/10grams.
After that, I have noticed improvement on the issue. It is still there but very minimal.
On a motorway it has also performed better by reduced vibration to barely feelable.

Still have plenty of life in the pads and disks so will not be able to determine if it was from them or not.

Would appreciate if you could update the thread, once find out more from your side

Sent from my CLT-L09 using Tapatalk
 
Yes, I'll update once I know more. I plan to replace rear disks/pads so will check calipers. I'm not sure if it's coming from front or rear though. Even when braking to a stop, so 1-2mph, I can feel pads grip then release as the wheels turn. As if pads stick for part of the rotation then release for the rest.

Sent from my Nexus 6P using Tapatalk
 
Sounds like a number of issues

Firstly when fitting new discs you should ensure the hub face is clean and rust free, normally the instructions in the box will say to fit the disc and then check with a dial test indicator that the run out is with in tolerance .
If it is not they suggest you rotate the disc and try again , very few people actually do this !!!

Secondly you should clean the carriers for the pads up and make sure the pads move freely , ensuring the correct contact area is greased with the correct grease, most manufactures now have there own specific type of grease to use .
It can also help to just file the paint off the
Parts of the pads that fit in the slider so that they will move more freely .

The number of cars we get in at work that have brake issues because even the basics haven’t been done is unbelievable .
 
When I fitted disks I did check with DTI - perfect result. No issue initially, this came later and again I have checked recently with DTI and still showing as perfect - but issue persists, so not down to inconsistencies in disks.

Also as you suggest I did clean the carriers and I even replaced the rubber slider pin sockets (gromets?) and slider pins on the front callipers.

The rear pads when last changed came with new spring clips (these that push over the tracks in the carrier providing a smooth surface for the pads to slide). I had to wire brush the carriers clean for them to accept the new clips, which I didn't feel were a perfect fit. I need to investigate these rear callipers I think. I will also do some testing with the car jacked up, testing brake release etc. Just need some better weather as I don't have a garage.
 
Just stripped out rear offside brake pads and removed disk. Not looking in great shape. Lots of bulging rust on outside edges of disk (outside of pad contact). Chipped off the rust and cleaned with wire wheel. Removing pads was a struggle as very tight on the sliders (where they slide over the clip placed on the carrier). Removed pads, took out the clips (is this what these metal shims are called?), and scraped out the rust layers from the carrier from under where the clips contact - thinking that the rust on the carrier was pushing the clips into the pads not giving them the required space to slide cleanly. Refitted everything (noted a small slice in the dust boot over the caliper piston). I refitted it all and went out for a test drive, giving very heavy brake application to get them nice and hot. Honestly not sure if there is any improvement, although this is just one brake looked at so far. Since doing this, I have just ordered a new set of disks and pads for the rear and a brake caliper servicing kit to replace those dust seals (enough to do both calipers). I'll inspect that caliper more closely when I replace the disks, to make sure the piston looks clean inside, hoping nothing got through that damaged dust seal. If necessary I'll remove the caliper and give it a full service (although hoping I don't have to go this far as could do without having to bleed brakes). If I do have to remove calipers, then I might give them a shot blast as they have major rust layers. Would also like to clean up the carriers, but these look to be a real PITA to remove - looks like long bolts through the back of the hubs with little access to the lower bolt.
 
Paul Atherton said:
Just stripped out rear offside brake pads and removed disk. Not looking in great shape. Lots of bulging rust on outside edges of disk (outside of pad contact). Chipped off the rust and cleaned with wire wheel. Removing pads was a struggle as very tight on the sliders (where they slide over the clip placed on the carrier). Removed pads, took out the clips (is this what these metal shims are called?), and scraped out the rust layers from the carrier from under where the clips contact - thinking that the rust on the carrier was pushing the clips into the pads not giving them the required space to slide cleanly. Refitted everything (noted a small slice in the dust boot over the caliper piston). I refitted it all and went out for a test drive, giving very heavy brake application to get them nice and hot. Honestly not sure if there is any improvement, although this is just one brake looked at so far. Since doing this, I have just ordered a new set of disks and pads for the rear and a brake caliper servicing kit to replace those dust seals (enough to do both calipers). I'll inspect that caliper more closely when I replace the disks, to make sure the piston looks clean inside, hoping nothing got through that damaged dust seal. If necessary I'll remove the caliper and give it a full service (although hoping I don't have to go this far as could do without having to bleed brakes). If I do have to remove calipers, then I might give them a shot blast as they have major rust layers. Would also like to clean up the carriers, but these look to be a real PITA to remove - looks like long bolts through the back of the hubs with little access to the lower bolt.
Click to expand...
Just to add, since getting the pads sliding cleanly on the rear offside carrier, I have noticed a definite improvement, now only very slight oscillation when braking (think this might be due to same issue on rear nearside caliper, which I haven't looked at yet). So for anyone with similar issue, would suggest cleaning up calipers to get free movement to pads.

Sent from my Nexus 6P using Tapatalk
 
  • Like
Reactions: KrisKrk
Thank you Paul.
Think, when the weather improves, Will give it a go myself.

Sent from my CLT-L09 using Tapatalk
 
You must log in or register to reply here.

Similar threads

Mercedes Traitor
S4 Brake Discs
Replies
3
Views
868
Mercedes Traitor
Mercedes Traitor
I
Brake discs size?.....
Replies
2
Views
11K
Ian3653
I
GAS MONKEY
Brake discs replacement
Replies
7
Views
979
desertstorm
desertstorm
matt.russell
Help .. Brake discs
Replies
2
Views
2K
Liquidfusion-S3
Liquidfusion-S3
Djwoody
Which Brake Pads & Discs?
Replies
27
Views
5K
SI-W85
SI-W85
Top
Back