M Carbon Ceramic Brakes - Serious Wheel Clearance Issue (rocks / stones)

[Geordie33]

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Fellow F8x enthusiasts,

BMW M3 M4 Carbon Ceramic Brakes Problems;

I reported this issue in Feb, it's now occurred 3 times on different OEM wheels.

The design clearance of the CCB to Standard 19" wheel rim is only ~5mm in places. This means that any small road stones larger than ~5mm will cause damage most road debris is easily this size. The tyres when dry pickup the stones into the wheel arch where they get thrown into the wheel. The issue is that the brake shield (steel pressing) which is unique to CCB application is inadequate to prevent the ingress of road stones into the central wheel area. You can see strong engineering development evidence in this CCB plate compared to standard brake plate on steels. It's obviously been a major issue during development phase and now BMW is having field reports / warranty on this. Worst damage was a 2 mm groove, which was a safety concern at dealer expert inspection.
No fix or containment has yet been announced. Any other similar experiences ? Would like to hear from you?

[Geordie33]

Here's how it happened, road was dry doing About 20mph one time and about 25mph the other. Tire picked up some small stones which rattled around in the Wheel (we all know this sound) for a few seconds BUT then a real loud dull scraping noise as the stones get stuck in the gap between the wheel and brake Caliper both times produced full circumference groves in the wheel barrel area adjacent to the Caliper at a minimum clearance. Of the 3 it's happened never heard the 1st one.
The stone get stuck at the bottom of the wheel rim in the barrel area and then the forward wheel rotation takes the stone into the Caliper which are mounted very low and rearward. Clearance is about 3-4mm in this area. This means it's likely to happen regularly, which it has!!

[Geordie33]

Shows Brake Caliper damage at lower edge you can see where the stone goes into the ~5mm gap and get forced thru causing the damage to the wheel at the same time.

[Mark's M]

Interesting post, thanks Geordie (and Carlos). It'll be something to watch for and appreciate the head's up. I'm shopping for cold weather/winter wheels now, well in advance of this November, so I'll definately pay attention to what I'm buying.

[Mark's M]

Originally Posted by Carlos@MORR

We were shocked to find the OEM clearance to be about 2-3mm on the barrel side. This is borderline close to the minimum recommended by Brembo. Very small clearance and im not surprised at all to see this happening to you.

We designed our new 19-inch forgings for the M3/M4 that are able to bring these tolerances up to 6-8mm. A much safer margin.

I'm glad to see its only cosmetic so far and haven't seen any reported rotor damage yet. Not sure what BMW can do to correct this.

Perhaps buy us a set of Morr wheels??? Lol, I wish!

[gogoevo]

Originally Posted by Geordie33

Fellow F8x enthusiasts,

I reported this issue in Feb, it's now occurred 3 times on different OEM wheels.

The design clearance of the CCB to Standard 19" wheel rim is only ~5mm in places. This means that any small road stones larger than ~5mm will cause damage most road debris is easily this size. The tyres when dry pickup the stones into the wheel arch where they get thrown into the wheel. The issue is that the brake shield (steel pressing) which is unique to CCB application is inadequate to prevent the ingress of road stones into the central wheel area. You can see strong engineering development evidence in this CCB plate compared to standard brake plate on steels. It's obviously been a major issue during development phase and now BMW is having field reports / warranty on this. Worst damage was a 2 mm groove, which was a safety concern at dealer expert inspection.
No fix or containment has yet been announced. Any other similar experiences ? Would like to hear from you?

I just observed the same thing on my wheels. Do you have the wheel and tire protection package, or was it simply a warranty matter?

[JoeFromPA]

FYI, I just want to share that I have this on my EIGHTEEN (18") wheels after 3200 miles of regular road use. 2 wheels have full circumferential grooves in the middle from what I'd guess are rocks getting stuck.

I've never seen this before on any wheel/vehicle. On the one hand, it upsets me. On the other, it's not readily visible on the 18" wheel from the outside and it doesn't appear to impact safety at this stage.

[gogoevo]

Exactly as you describe, only mine are painfully obvious. I hope BMW makes this right. I'm also concerned about the HRE's (19) that I have yet to receive. I afraid to mount them at this point.

[Geordie33]

M-Division Engineering are aware of this issue even since Press cars. So at least one year. If they plan to fix it (it's a potential safety concern in the failure mode) then we should expect a production containment at minimum, a shield redesign or a move to a wheel with larger clearance. I am going to give them 3 weeks to come up with a fix or take them to task. My local BMW Dealer has been first Class in understanding the physics of the problem. Come on M Division we are waiting for your brilliant engineering fix!

[Geordie33]

Picture added: please note how stones enter athe gap at lower edge of Caliper and get dragged though by the rotating wheel rim.

[gogoevo]

Originally Posted by Geordie33

M-Division Engineering are aware of this issue even since Press cars. So at least one year. If they plan to fix it (it's a potential safety concern in the failure mode) then we should expect a production containment at minimum, a shield redesign or a move to a wheel with larger clearance. I am going to give them 3 weeks to come up with a fix or take them to task. My local BMW Dealer has been first Class in understanding the physics of the problem. Come on Klaus Dullinger @ M Division we are waiting your engineering fix!

Have you received new wheels? And if so, were the new wheels warrantied?

[Geordie33]

Car has had 2 new wheels at BMW expense..... Current new wheel is as pictures....3/4 front wheels damage

[Geordie33]

...point is replacing is futile...it is a design issue.

[gogoevo]

Originally Posted by Geordie33

...point is replacing is futile...it is a design issue.

Agreed. I'm just wondering if replacing wheels (as needed) will be enough to compel BMW to correct the issue.

[Gearhead999s]

Used to have this issue with my 18" track setup on my e92 with a 380mm Stoptech BBK.It is not a big deal or at least in my case the marks were more superficial than structural.However if my factory stock car was doing this I would be quite upset.

[Mark's M]

Originally Posted by Geordie33

Car has had 2 new wheels at BMW expense..... Current new wheel is as pictures....3/4 front wheels damage

Wow...and thanks for the extra pics. Wonder how they didn't foresee a 2-3mm clearance being a problem? And how much has it cost BMW to replace your wheels thus far, an exercise that appears like it's going to be regular occurrence?

I joked about BMW supplying CCB customers with a set of 20's in the sister thread to this one.....maybe not such a joke if this keeps up!!

[Geordie33]

Currently this issue is with M Division, I suggest all of you with issues push for a resolution also. For me it's a clear recall.......not fit for function normal road driving. I heard 2 of my 4 issues happen its 20-30mph driving.
BTW I am in the Automotive business at a professional engineering level. I know what this looks like from the OEM standpoint. I won't let this one go. Maybe later I will ask to collect all VIN numbers effected and expedite thru legal.

[M2wolf]

WOW! Am glad I did not opt for the £6K option for CCBs..

sorry to hear about that, but good to know BMW has replaced your alloys for new under warranty.. but agreed.. it's a design flaw.. so hopefully they'll come out with a proper solution!

[AM4ZING]

Originally Posted by Geordie33

M-Division Engineering are aware of this issue even since Press cars. So at least one year. If they plan to fix it (it's a potential safety concern in the failure mode) then we should expect a production containment at minimum, a shield redesign or a move to a wheel with larger clearance. I am going to give them 3 weeks to come up with a fix or take them to task. My local BMW Dealer has been first Class in understanding the physics of the problem. Come on Klaus Dullinger @ M Division we are waiting your engineering fix!

Keep up updated. I am awaiting delivery of my M4 with CCB option and have read too many horror stories

[nbennettksu]

Originally Posted by Geordie33

Currently this issue is with M Division, I suggest all of you with issues push for a resolution also. For me it's a clear recall.......not fit for function normal road driving. I heard 2 of my 4 issues happen its 20-30mph driving.
BTW I am in the Automotive business at a professional engineering level. I know what this looks like form the OEM standpoint. I won't let this one go. Maybe later I will ask to collect all VIN numbers effected and expedite thru legal.

Recalls are safety related (here in the US anyways), which this isn't. At best, you'd be hoping for some kind of campaign; not a recall

Nonetheless, this sucks!

[gogoevo]

Originally Posted by nbennettksu

Recalls are safety related (here in the US anyways), which this isn't. At best, you'd be hoping for some kind of campaign; not a recall

Nonetheless, this sucks!

I don't know. I would think it would only get worse over time, removing more and more material from the wheel, and thus weakening the wheel leading to wheel failure.

[nbennettksu]

Originally Posted by gogoevo

I don't know. I would think it would only get worse over time, removing more and more material from the wheel, and thus weakening the wheel leading to wheel failure.

valid point