Warped discs due to over torqued wheel nuts?
Discussion
Hey Folks,
Been having a nightmare with brakes on a new (to me) car.
Long story short Audi inspected car in Dec after I reported vibration braking from 30-20mph. They said everything was fine... Used sales manager said to take it back if I wasn't happy at a later date.
I persevered for another 1k miles but still not happy, now Audi confirm in their words "warped discs", but they refuse to take any responsibility blaming the fact I had winter wheels fitted.
They're saying that the wheel nuts must have been over torqued and so warped the discs. But they have no evidence to support this, no visible damage to bell housing on discs and no measurable indication on bell at all (floating discs).
So I feel like they're full of BS and trying to save themselves the £2k they're trying to charge me.
Has anyone had warped discs due to over-torq? To be honest i've been fettling cars for 20yrs and never heard of this, let alone experienced it.
Web searches throw up a couple of results but not much.
Ta
Been having a nightmare with brakes on a new (to me) car.
Long story short Audi inspected car in Dec after I reported vibration braking from 30-20mph. They said everything was fine... Used sales manager said to take it back if I wasn't happy at a later date.
I persevered for another 1k miles but still not happy, now Audi confirm in their words "warped discs", but they refuse to take any responsibility blaming the fact I had winter wheels fitted.
They're saying that the wheel nuts must have been over torqued and so warped the discs. But they have no evidence to support this, no visible damage to bell housing on discs and no measurable indication on bell at all (floating discs).
So I feel like they're full of BS and trying to save themselves the £2k they're trying to charge me.
Has anyone had warped discs due to over-torq? To be honest i've been fettling cars for 20yrs and never heard of this, let alone experienced it.
Web searches throw up a couple of results but not much.
Ta
Yeah afraid so, initially thought it just needed run in as it had been sat on the forecourt. It's not a major vibration, and very specific at 30-20mph when braking hard.
I didn't even notice for the 1st few weeks I don't tend to emergency stop all the time, it was just when someone pulled out on me that I hit the brakes hard and noticed it.
But it's been a constant issue the entire time i've had it now, luckily not getting any worse but it's just irritating.
Dealer inspected the car less than a month / 1k miles after I collected it, (7days after the winter wheels went on) and told me all was fine, but any lasting issues and they'll replace the discs...
I complained again now after another 1k miles that i'm still not happy, they look at car and now confirm brake discs "warped" but that it must have been the wheels being over torqued when fitted!
I've pointed out that they already said they were fine with the same wheels on previously, and questioned how it could suddenly be that causing the issue, and that if they're mechanically damaged in this way there must be evidence, but to no avail.
Eugh.
wide1 said:
Been having a nightmare with brakes on a new (to me) car.
Long story short Audi inspected car in Dec after I reported vibration braking from 30-20mph. They said everything was fine... Used sales manager said to take it back if I wasn't happy at a later date.
I persevered for another 1k miles but still not happy, now Audi confirm in their words "warped discs", but they refuse to take any responsibility blaming the fact I had winter wheels fitted.
They're saying that the wheel nuts must have been over torqued and so warped the discs. But they have no evidence to support this, no visible damage to bell housing on discs and no measurable indication on bell at all (floating discs).
So I feel like they're full of BS and trying to save themselves the £2k they're trying to charge me.
Has anyone had warped discs due to over-torq? To be honest i've been fettling cars for 20yrs and never heard of this, let alone experienced it.
How CAN it happen?Long story short Audi inspected car in Dec after I reported vibration braking from 30-20mph. They said everything was fine... Used sales manager said to take it back if I wasn't happy at a later date.
I persevered for another 1k miles but still not happy, now Audi confirm in their words "warped discs", but they refuse to take any responsibility blaming the fact I had winter wheels fitted.
They're saying that the wheel nuts must have been over torqued and so warped the discs. But they have no evidence to support this, no visible damage to bell housing on discs and no measurable indication on bell at all (floating discs).
So I feel like they're full of BS and trying to save themselves the £2k they're trying to charge me.
Has anyone had warped discs due to over-torq? To be honest i've been fettling cars for 20yrs and never heard of this, let alone experienced it.
The bit that causes braking vibration isn't even the same bit of the disc as the bit that contacts the wheel mounting face. The mounting face is sandwiched between the hub and the wheel. If the wheel fasteners were MONUMENTALLY over-tightened, the threads would stretch WAY before the disc itself would distort in any way...
Oh, hold on - FLOATING discs? So they're not even the same bit of metal...? I'm not sure it changes the theory - because any distortion would translate to the bobbins that connect the friction surface to the bell, but...
Nah, they're bulls
tting.wide1 said:
They're saying that the wheel nuts must have been over torqued and so warped the discs. But they have no evidence to support this, no visible damage to bell housing on discs and no measurable indication on bell at all (floating discs).
Ta
Go back to whoever told you this and ask in response " Are you a fu.cking Moron ?"Ta
And do this loudly and ideally whilst recording it so everyone can see and then hear their response. Also bring a can of spray foam/cream etc and everytime they try to come off with some other BS, spray them.
stevieturbo said:
Go back to whoever told you this and ask in response " Are you a fu.cking Moron ?"
And do this loudly and ideally whilst recording it so everyone can see and then hear their response. Also bring a can of spray foam/cream etc and everytime they try to come off with some other BS, spray them.
Please do this And do this loudly and ideally whilst recording it so everyone can see and then hear their response. Also bring a can of spray foam/cream etc and everytime they try to come off with some other BS, spray them.
Quote " didn't even notice for the 1st few weeks I don't tend to emergency stop all the time, it was just when someone pulled out on me that I hit the brakes hard and noticed it."
That's your ABS pulsing the brakes to stop the wheels locking. Typically only noticed in an emergency stop.
If it continues, then the ABS thinks you have a locking wheel all the time.
Wheel reluctor rings? ABS itself?
JOhn
That's your ABS pulsing the brakes to stop the wheels locking. Typically only noticed in an emergency stop.
If it continues, then the ABS thinks you have a locking wheel all the time.
Wheel reluctor rings? ABS itself?
JOhn
Some people reckon there’s no such thing as warped discs, but some cars seem susceptible to leaving pad deposits on the disc and that produces the same effect.
What are the discs like on the inside face? I have a little used Merc And the discs on the outer face cleaned up fine but rust built up on the inner face and that vibrated under braking.
What are the discs like on the inside face? I have a little used Merc And the discs on the outer face cleaned up fine but rust built up on the inner face and that vibrated under braking.
To confirm, it's not ABS pulsing. On the extremely rare occasions the ABS comes on I've more important things to worry about than brake feel... like clean underwear!
The dealer have stated warping, but as you mention I imagine it's actually going to be uneven deposits. They still have the car so I can't visually inspect yet.
The dealer have stated warping, but as you mention I imagine it's actually going to be uneven deposits. They still have the car so I can't visually inspect yet.
Sheepshanks said:
but some cars seem susceptible to leaving pad deposits on the disc and that produces the same effect.
A more likely cause than "warped" discs. A cure that's worked for me in the past is to give them a really good workout - several really hard stops from 70-ish mph. Good fun even if it doesn't work.Another possible cause is crap pads.
Dave Brand said:
Sheepshanks said:
but some cars seem susceptible to leaving pad deposits on the disc and that produces the same effect.
A more likely cause than "warped" discs. A cure that's worked for me in the past is to give them a really good workout - several really hard stops from 70-ish mph. Good fun even if it doesn't work.The M25 at 8am on a Monday morning is probably not the best place to try this.
Not impossible that it could be overtorqued wheel nuts, particularly if they have been tightened in the wrong order (they should be tightened every other one on a five stud, not in a circle) but it’s unlikely.
That said which Audi is it? If it’s a higher performance one with semi-floating pin drive discs on aluminium bells it may be more susceptible to bell distortion from tightening torque/pattern.
Really though the wheel/disc/hub faces should be designed not to be sensitive to it on a road car. We’ve recommended wheel contact face design changes for this exact reason before, although obviously if they’re grossly overtightened then you can’t really complain.
Whichever way I’d expect to see high quality runout/DTV measurements from something like a brakeview on the car, ideally with and without the wheels fitted. It’s easy to prove and you’d expect a clear star pattern corresponding to the number of studs/bolts. If they’ve just assumed it without measuring then it’s probably a known problem in which case it shouldn’t be your problem.
Far more likely it’s either a poorly manufactured disc, wheel with an uneven mounting face or it’s calipers without enough fallback (ie running clearance) that have caused DTV.
Also worth pointing out that 20mph is a very low speed for this to happen, it must be pretty serious DTV or epic runout to be noticeable at that speed.
I’d recommend escalating it with Audi, ultimately it’s their brake supplier that will be getting the grief and I’ve certainly been sent out to far more minor issues than this!
That said which Audi is it? If it’s a higher performance one with semi-floating pin drive discs on aluminium bells it may be more susceptible to bell distortion from tightening torque/pattern.
Really though the wheel/disc/hub faces should be designed not to be sensitive to it on a road car. We’ve recommended wheel contact face design changes for this exact reason before, although obviously if they’re grossly overtightened then you can’t really complain.
Whichever way I’d expect to see high quality runout/DTV measurements from something like a brakeview on the car, ideally with and without the wheels fitted. It’s easy to prove and you’d expect a clear star pattern corresponding to the number of studs/bolts. If they’ve just assumed it without measuring then it’s probably a known problem in which case it shouldn’t be your problem.
Far more likely it’s either a poorly manufactured disc, wheel with an uneven mounting face or it’s calipers without enough fallback (ie running clearance) that have caused DTV.
Also worth pointing out that 20mph is a very low speed for this to happen, it must be pretty serious DTV or epic runout to be noticeable at that speed.
I’d recommend escalating it with Audi, ultimately it’s their brake supplier that will be getting the grief and I’ve certainly been sent out to far more minor issues than this!
TooMany2cvs said:
wide1 said:
Been having a nightmare with brakes on a new (to me) car.
Long story short Audi inspected car in Dec after I reported vibration braking from 30-20mph. They said everything was fine... Used sales manager said to take it back if I wasn't happy at a later date.
I persevered for another 1k miles but still not happy, now Audi confirm in their words "warped discs", but they refuse to take any responsibility blaming the fact I had winter wheels fitted.
They're saying that the wheel nuts must have been over torqued and so warped the discs. But they have no evidence to support this, no visible damage to bell housing on discs and no measurable indication on bell at all (floating discs).
So I feel like they're full of BS and trying to save themselves the £2k they're trying to charge me.
Has anyone had warped discs due to over-torq? To be honest i've been fettling cars for 20yrs and never heard of this, let alone experienced it.
How CAN it happen?Long story short Audi inspected car in Dec after I reported vibration braking from 30-20mph. They said everything was fine... Used sales manager said to take it back if I wasn't happy at a later date.
I persevered for another 1k miles but still not happy, now Audi confirm in their words "warped discs", but they refuse to take any responsibility blaming the fact I had winter wheels fitted.
They're saying that the wheel nuts must have been over torqued and so warped the discs. But they have no evidence to support this, no visible damage to bell housing on discs and no measurable indication on bell at all (floating discs).
So I feel like they're full of BS and trying to save themselves the £2k they're trying to charge me.
Has anyone had warped discs due to over-torq? To be honest i've been fettling cars for 20yrs and never heard of this, let alone experienced it.
The bit that causes braking vibration isn't even the same bit of the disc as the bit that contacts the wheel mounting face. The mounting face is sandwiched between the hub and the wheel. If the wheel fasteners were MONUMENTALLY over-tightened, the threads would stretch WAY before the disc itself would distort in any way...
Oh, hold on - FLOATING discs? So they're not even the same bit of metal...? I'm not sure it changes the theory - because any distortion would translate to the bobbins that connect the friction surface to the bell, but...
Nah, they're bulls
tting.Whatever distortion there is at the mounting face will be multiplied up by the time it gets to the friction ring, so in reality it takes cock all to create a problem.
Plus if it’s a low offset disc then it will be relatively flat and it won’t have much inherent stiffness to resist any distortion.
Only spotted the OP’s comment about floating discs after I wrote my last post, chances are on an Audi that it’s a pin drive semi-floating disc like I mentioned rather than a proper floating design. These allow radial float for thermal expansion, they don’t have any axial float.
Having said that I’ve seen and measured a car with one of our fully floating track spec kits (albeit with sprung bobbins to prevent rattle) that had a recurrent judder problem.
Massively unusual for us, particularly as the car was running near standard power when there are owners running double the power on track quite happily on our kits. We went through everything meticulously and the only fault we could find was poorly manufactured hub mounting surfaces, one of which had about 40 microns of runout. It produced a measurable runout change on a new set of discs when the wheels were tightened. Our distributor replaced the hubs and the car hasn’t been back since.
Edited by The Wookie on Friday 23 February 20:38
Thanks for the in depth input wookie, much appreciated.
It's a 64 plate RS4.
I've heard nothing from audi dealer at all today, so either they've sent it up the food chain or they're just incompetent and rude (They still need to return my car and pick up the courtesy car I have).
The service techs have already proven to be incompetent (I had to inform them of the service schedule for example) so who knows...
So to try and prove this one way or the other I should demand a brakeview test be carried out?
Thanks again
It's a 64 plate RS4.
I've heard nothing from audi dealer at all today, so either they've sent it up the food chain or they're just incompetent and rude (They still need to return my car and pick up the courtesy car I have).
The service techs have already proven to be incompetent (I had to inform them of the service schedule for example) so who knows...
So to try and prove this one way or the other I should demand a brakeview test be carried out?
Thanks again
wide1 said:
Worth repeating is the fact that audi inspected the car in Dec, after wheels were fitted and said it was fine.
Now they confirm "warped discs", but suddenly it's been caused by wheel fitting...
They can't have it both ways!
Presumably the inspection in Dec involved removing the wheels, so if it was OK at that point the subsequent "over torque" was done by them when they refitted them. No?Now they confirm "warped discs", but suddenly it's been caused by wheel fitting...
They can't have it both ways!
No probs!
Just had a look, if I’ve googled the right images they are indeed pin drive and look like quite a low offset so wouldn’t be surprised if the setup was sensitive to issues.
If they were the last ones to refit the wheels then it’s a pretty daft argument anyway
Brakeview is just one system used to measure DTV and runout, but you should certainly demand that they take some proper measurements and justify their answers. They should also be checking for brake drag, hub runout and any premature wear in the bushes. If they’re still stuck for ideas then they should be kicking it up the chain, ultimately to the brake supplier, rather than fobbing you off.
The only thing to be aware of is that if you have used the car on track then the results might be a rod for your own back, but typically it’s pretty obvious if the brakes have taken a pasting!
ETA, one thing to note is that the runout might happen straight away, but the judder won’t as it’s almost always DTV, unless the runout is epic. The DTV usually happens in motorway driving where the high spots of the runout are gradually worn off the discs in the off brake condition. The resulting thickness variation then creates torque and pressure pulses which give you the feeling of judder through the wheel and pedal
Just had a look, if I’ve googled the right images they are indeed pin drive and look like quite a low offset so wouldn’t be surprised if the setup was sensitive to issues.
If they were the last ones to refit the wheels then it’s a pretty daft argument anyway
Brakeview is just one system used to measure DTV and runout, but you should certainly demand that they take some proper measurements and justify their answers. They should also be checking for brake drag, hub runout and any premature wear in the bushes. If they’re still stuck for ideas then they should be kicking it up the chain, ultimately to the brake supplier, rather than fobbing you off.
The only thing to be aware of is that if you have used the car on track then the results might be a rod for your own back, but typically it’s pretty obvious if the brakes have taken a pasting!
ETA, one thing to note is that the runout might happen straight away, but the judder won’t as it’s almost always DTV, unless the runout is epic. The DTV usually happens in motorway driving where the high spots of the runout are gradually worn off the discs in the off brake condition. The resulting thickness variation then creates torque and pressure pulses which give you the feeling of judder through the wheel and pedal
Edited by The Wookie on Saturday 24th February 00:52
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