E92 M3 - brakes
Discussion
Right. After some hard use recently, I think the brake discs may be warped in my M3. I get quite bad judder under braking (light or hard), and at slow speeds and very light braking, the stopping force is not consistent.
Has anyone else had this experience? What's the deal with regards to warranty; brake fade and heavy pad/disc wear I can stomach, but actually warping discs seems to be a design fault to me. (Completely standard car.)
Has anyone else had this experience? What's the deal with regards to warranty; brake fade and heavy pad/disc wear I can stomach, but actually warping discs seems to be a design fault to me. (Completely standard car.)
edb49 said:
Right. After some hard use recently, I think the brake discs may be warped in my M3. I get quite bad judder under braking (light or hard), and at slow speeds and very light braking, the stopping force is not consistent.
Has anyone else had this experience? What's the deal with regards to warranty; brake fade and heavy pad/disc wear I can stomach, but actually warping discs seems to be a design fault to me. (Completely standard car.)
You'd need to define hard use really?? I doubt it's a design fault so hard use would cause such failings.Has anyone else had this experience? What's the deal with regards to warranty; brake fade and heavy pad/disc wear I can stomach, but actually warping discs seems to be a design fault to me. (Completely standard car.)
Had the same thing happen to my lightly tuned B7 RS4 during a 5 day Ring fest last year. Front discs were proper fooked (judder under all braking) & dealer confirmed they were quite badly warped. Not quite dangerous but defo needed replacing.
In three years VERY hard, but totally road use, a mate got through SIX (!) sets of front discs on his E46 M3. I've truly never met anyone who brakes as late or as hard as he does on the road. BMW sorted under warranty every time with no quibbles -which was nice. Even better if they'd learn to give the 'ultimate driving machine' decent brakes. Haven't got your problems yet mate but I'm detecting 'tiredness' in mine and haven't been on track seriously yet.
Very rarely do you actually 'warp' discs, the problem you speak of is usually as a result of uneven pad deposits which can arise as a result of poor initial bedding in, or for example dragging the brakes rather than firm engagement and disengagement. It very much depends on the pad material and driving style but can usually either by cured by re-bedding the pads/discs in, or if the pad material is not abrasive enough then you could fit a more abrasive pad to clean off the disc and prepare for re-bedding in (or remove the discs and machine them clean again). Usually that's far to difficult to explain to most customers, so its usually easier for dealers to just say "discs are warped" and just replace them.
Edited by DoctorD on Monday 14th January 22:34
To be honest, if the E92 has the same sliding caliper cast iron calipers that all M cars have then the issue is not going to go away, whether it is pad pickup or real warping. Those great big cast iron calipers just retain heat like an Aga, so gently bake all the pad deposits and slowly warp your disks over time. If you want to check that the disks are warped, any good garage should be able to check the runout and you can see on the dial gauge what's going on. I went through all the same grief with my E30 M3 and in the end gave up with the standard setup. It is just too compromised for serious use, they would be great for a short period of hard use then all the juddering would be back. New disks, pads, refacing the disks, re-bedding etc etc, all worked up to a point but soon enough you ended up back at square one. The next thing I considered was that it was my technique, was I dragging the brakes too much, rather than just hitting them hard and then off. This seemed to make little difference. In the end, I hit the credit card and installed a set of AP's up front. Best money I have ever spent on an upgrade, ever. In the 3 years they have been on the car, I have pounded them at track days, trickled along on the road in traffic, wet/dry, it doesn't matter. They just work. No judder, no fade, no maintenence (or very little, checking and cleaning after intial bed in). Still on the same set of pads and disks. I hope you get it sorted because I have been there and now how much of a pain in the rear it is, in the end it was spoiling my enjoyment of the car which is why I bit the bullet.
Edb, how many miles has your car done? Any heavy work? My car has done some mileage, a trackday and my brakes are excellent. The Callipers look to be 4 or two piston sliders, which is an advance on the old E46 garbage.
Interestingly, my experince of CSL ownership was this. BMW disks superb / callipers cheapo rubbish. AP disks appalling / callipers nice. Unfortunately the two didn't mix.
SteveD is nearly right, but it is a bit more complicated. Basically what happens is the warping is not in any lateral deformation (like a wafer thin Cortina disk would wobble), but is changes in the coefficient of friction across the surface due to the annealing effect (slow heat treatment) of very hot pads cooling in one area. Repeated stopping at the same point will soften the metal and make it more slippy, so a change in grip as the wheel rotates whilst braking. This sets up a shudder, and due to the harmonics in the front suspension, this can amplify into some really horrible wobbling.
Usually the Ate (I think that is who make them) OEM disks are excellent and last for ages. Just do not be tempted to buy AP / Brembo / PF disks until you have sorted and tried different pads and hoses.
And if you have been using on track, cool them down nicely and mind the pads. OEM stuff from BMW usually comes from a Gorge in Somerset...
Interestingly, my experince of CSL ownership was this. BMW disks superb / callipers cheapo rubbish. AP disks appalling / callipers nice. Unfortunately the two didn't mix.
SteveD is nearly right, but it is a bit more complicated. Basically what happens is the warping is not in any lateral deformation (like a wafer thin Cortina disk would wobble), but is changes in the coefficient of friction across the surface due to the annealing effect (slow heat treatment) of very hot pads cooling in one area. Repeated stopping at the same point will soften the metal and make it more slippy, so a change in grip as the wheel rotates whilst braking. This sets up a shudder, and due to the harmonics in the front suspension, this can amplify into some really horrible wobbling.
Usually the Ate (I think that is who make them) OEM disks are excellent and last for ages. Just do not be tempted to buy AP / Brembo / PF disks until you have sorted and tried different pads and hoses.
And if you have been using on track, cool them down nicely and mind the pads. OEM stuff from BMW usually comes from a Gorge in Somerset...
phatgixer said:
Edb, how many miles has your car done? Any heavy work? My car has done some mileage, a trackday and my brakes are excellent. The Callipers look to be 4 or two piston sliders, which is an advance on the old E46 garbage.
I've done 3.5k miles in mine now, which includes about 3-4 hours of hard work at Bedford. edb49 said:
phatgixer said:
Edb, how many miles has your car done? Any heavy work? My car has done some mileage, a trackday and my brakes are excellent. The Callipers look to be 4 or two piston sliders, which is an advance on the old E46 garbage.
I've done 3.5k miles in mine now, which includes about 3-4 hours of hard work at Bedford. The OEM pads have overheated and deposited some poop on the disk, and hopefully this will be cleaned off with the hard compound pads. If you have annealed the disks, they are scrap.
Tip children: In a BMW do not track your car with standard pads. If you must, 3 laps max at a sitting and only 2 at Bedford GT.
DoctorD said:
Very rarely do you actually 'warp' discs, the problem you speak of is usually as a result of uneven pad deposits which can arise as a result of poor initial bedding in, or for example dragging the brakes rather than firm engagement and disengagement. It very much depends on the pad material and driving style but can usually either by cured by re-bedding the pads/discs in, or if the pad material is not abrasive enough then you could fit a more abrasive pad to clean off the disc and prepare for re-bedding in (or remove the discs and machine them clean again). Usually that's far to difficult to explain to most customers, so its usually easier for dealers to just say "discs are warped" and just replace them.
That's true & tbh warped is an over used term, but very heavy use can & often does cause the discs to lose their true shape & as such you'll get vibration under all braking conditions. Not sure a few hrs of back road usage would cause this unless you didn't cool the brakes down.Edited by DoctorD on Monday 14th January 22:34
On my RS4, i got 6 days of heavy Nordschleife usage out of OEM pads & discs & was at times doing 8:29 BTG laps, so was not hanging about & only upon my return to the UK did the pads need replacing, although the brake discs did start offering vibration as the week went on.
W8PMC said:
DoctorD said:
Very rarely do you actually 'warp' discs, the problem you speak of is usually as a result of uneven pad deposits which can arise as a result of poor initial bedding in, or for example dragging the brakes rather than firm engagement and disengagement. It very much depends on the pad material and driving style but can usually either by cured by re-bedding the pads/discs in, or if the pad material is not abrasive enough then you could fit a more abrasive pad to clean off the disc and prepare for re-bedding in (or remove the discs and machine them clean again). Usually that's far to difficult to explain to most customers, so its usually easier for dealers to just say "discs are warped" and just replace them.
That's true & tbh warped is an over used term, but very heavy use can & often does cause the discs to lose their true shape & as such you'll get vibration under all braking conditions. Not sure a few hrs of back road usage would cause this unless you didn't cool the brakes down.Edited by DoctorD on Monday 14th January 22:34
On my RS4, i got 6 days of heavy Nordschleife usage out of OEM pads & discs & was at times doing 8:29 BTG laps, so was not hanging about & only upon my return to the UK did the pads need replacing, although the brake discs did start offering vibration as the week went on.
edb49 said:
What's the diagnosis then, get another set of hard pads and do a track day?
That may work if it is due to deposits. If the disk is misshapen, annealed or too thin, then other medication needed.If you are doing another trackday, then fine, give it a go, if not I would get the disks inspected and skimmed if apprpriate, or fit new ones if heat damaged. Next time you go on track (except the Ring which is very light on brakes) fit harder pads that handle the heat better tham OEM. Not sure what fitments the E92 M3 take. Have a look at the pagid catalogue.
Pugsey said:
W8PMC said:
DoctorD said:
Very rarely do you actually 'warp' discs, the problem you speak of is usually as a result of uneven pad deposits which can arise as a result of poor initial bedding in, or for example dragging the brakes rather than firm engagement and disengagement. It very much depends on the pad material and driving style but can usually either by cured by re-bedding the pads/discs in, or if the pad material is not abrasive enough then you could fit a more abrasive pad to clean off the disc and prepare for re-bedding in (or remove the discs and machine them clean again). Usually that's far to difficult to explain to most customers, so its usually easier for dealers to just say "discs are warped" and just replace them.
That's true & tbh warped is an over used term, but very heavy use can & often does cause the discs to lose their true shape & as such you'll get vibration under all braking conditions. Not sure a few hrs of back road usage would cause this unless you didn't cool the brakes down.Edited by DoctorD on Monday 14th January 22:34
On my RS4, i got 6 days of heavy Nordschleife usage out of OEM pads & discs & was at times doing 8:29 BTG laps, so was not hanging about & only upon my return to the UK did the pads need replacing, although the brake discs did start offering vibration as the week went on.
The 997 GT3RS has magnificent brakes as standard (PCCB or Steel) and the 996 steel setup is always peerless. I have a set of fully floating brembos on my 996 (as the PCCBs shat themselves) and they are as good as the standard stuff, just much noisier!phatgixer said:
Pugsey said:
W8PMC said:
DoctorD said:
Very rarely do you actually 'warp' discs, the problem you speak of is usually as a result of uneven pad deposits which can arise as a result of poor initial bedding in, or for example dragging the brakes rather than firm engagement and disengagement. It very much depends on the pad material and driving style but can usually either by cured by re-bedding the pads/discs in, or if the pad material is not abrasive enough then you could fit a more abrasive pad to clean off the disc and prepare for re-bedding in (or remove the discs and machine them clean again). Usually that's far to difficult to explain to most customers, so its usually easier for dealers to just say "discs are warped" and just replace them.
That's true & tbh warped is an over used term, but very heavy use can & often does cause the discs to lose their true shape & as such you'll get vibration under all braking conditions. Not sure a few hrs of back road usage would cause this unless you didn't cool the brakes down.Edited by DoctorD on Monday 14th January 22:34
On my RS4, i got 6 days of heavy Nordschleife usage out of OEM pads & discs & was at times doing 8:29 BTG laps, so was not hanging about & only upon my return to the UK did the pads need replacing, although the brake discs did start offering vibration as the week went on.
The 997 GT3RS has magnificent brakes as standard (PCCB or Steel) and the 996 steel setup is always peerless. I have a set of fully floating brembos on my 996 (as the PCCBs shat themselves) and they are as good as the standard stuff, just much noisier!phatgixer said:
SteveD is nearly right, but it is a bit more complicated. Basically what happens is the warping is not in any lateral deformation (like a wafer thin Cortina disk would wobble), but is changes in the coefficient of friction across the surface due to the annealing effect (slow heat treatment) of very hot pads cooling in one area. Repeated stopping at the same point will soften the metal and make it more slippy, so a change in grip as the wheel rotates whilst braking. This sets up a shudder, and due to the harmonics in the front suspension, this can amplify into some really horrible wobbling.
Thanks for pointing that out Angus, you are of course correct but most people don't get as far as the discs losing shape before assuming they are warped. Driving style can make a huge difference as has already been pointed out, however it's a shame that their 'fitness for purpose' isn't more aligned with the target populace who actually buy the car. Strangely the problems I've found with //M cars have rarely been repeated with non-M BMWs despite traversing the same roads at similar speeds, so pad material has a lot to do with it and sometimes a change in pad material whilst using the same pig-iron calipers can make all the difference.
DoctorD said:
it's a shame that their 'fitness for purpose' isn't more aligned with the target populace who actually buy the car. Strangely the problems I've found with //M cars have rarely been repeated with non-M BMWs despite traversing the same roads at similar speeds, so pad material has a lot to do with it and sometimes a change in pad material whilst using the same pig-iron calipers can make all the difference.
Two excellent points. Although it seems to have become traditional we really shouldn't be having this conversation about an M car brakes on a regular basis should we - and it would certainly add very little cost to the car if BMW sorted the brakes. On reflection, like DocD, it's been my experience too that M car brakes seem to wilt - even on road - sooner than most others. Come on BMW, break (sorry) with tradition on the next one - the CSL maybe. I was once told BMW didn't make their brakes stronger for fear that other componenents deeper in the suspension set up might not take the strain - surely not true? Gassing Station | M Power | Top of Page | What's New | My Stuff