M40i brakes - design flaw uncovered

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Jim S
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M40i brakes - design flaw uncovered

Post by Jim S » Tue Jan 05, 2021 9:44 am

Sorry to hear of your problem climbbike but I am not at all surprised as it has happened to me five times now. In fact, it was me who first reported this problem and started this thread. :headbang:
If it is any consolation, I think that when the tyres wear down a bit they become less prone to throwing up stones and the problem is less likely to happen as time goes by. That has benn my experience anyway. :driving:

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M40i brakes - design flaw uncovered

Post by Jim S » Tue Jan 05, 2021 9:52 am

john-e89 wrote: Tue Jan 05, 2021 9:43 am It wouldn’t be too difficult to make an ally plate to cover the top what...quarter or the disc I’d think to deflect a falling stone, the issue is attaching it. I keep wondering if the techs would make a note of 3 small holes drilled in the cars backplate and use it to void warranty even though it would have zero effect...? You’d remove the home fitted ‘shield’ prior to a service but it’s the holes that’s the problem. :?
Yes, something fitted over the gap at the top of the heat shield would, most likely, prevent stones from getting in between the front rotors and heat shield. However, the gap between the shield and the wheel rim is very small so I think it would require a different shield design.

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M40i brakes - design flaw uncovered

Post by john-e89 » Tue Jan 05, 2021 9:58 am

Jim S wrote: Tue Jan 05, 2021 9:52 am
john-e89 wrote: Tue Jan 05, 2021 9:43 am It wouldn’t be too difficult to make an ally plate to cover the top what...quarter or the disc I’d think to deflect a falling stone, the issue is attaching it. I keep wondering if the techs would make a note of 3 small holes drilled in the cars backplate and use it to void warranty even though it would have zero effect...? You’d remove the home fitted ‘shield’ prior to a service but it’s the holes that’s the problem. :?
Yes, something fitted over the gap at the top of the heat shield would, most likely, prevent stones from getting in between the front rotors and heat shield. However, the gap between the shield and the wheel rim is very small so I think it would require a different shield design.
I was thinking of attaching it to the inside of the shield Jim, thus not making it any higher then the top of the shield, in fact a good few mm’s below the top.
M roady...OEM CSL’s, strut brace, Remus back boxes, ZHP, Intravee.
MR2 MK 2
E89 35i project car...mapped 365bhp, M4 stoppers & wheels, KWV3’s, H&R front ARB, M3 front arms, strut brace, Eisenmann cat back race exhaust, VRSF downpipes inbound.

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Jim S
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M40i brakes - design flaw uncovered

Post by Jim S » Tue Jan 05, 2021 10:24 am

john-e89 wrote: Tue Jan 05, 2021 9:58 am
Jim S wrote: Tue Jan 05, 2021 9:52 am
john-e89 wrote: Tue Jan 05, 2021 9:43 am It wouldn’t be too difficult to make an ally plate to cover the top what...quarter or the disc I’d think to deflect a falling stone, the issue is attaching it. I keep wondering if the techs would make a note of 3 small holes drilled in the cars backplate and use it to void warranty even though it would have zero effect...? You’d remove the home fitted ‘shield’ prior to a service but it’s the holes that’s the problem. :?
Yes, something fitted over the gap at the top of the heat shield would, most likely, prevent stones from getting in between the front rotors and heat shield. However, the gap between the shield and the wheel rim is very small so I think it would require a different shield design.
I was thinking of attaching it to the inside of the shield Jim, thus not making it any higher then the top of the shield, in fact a good few mm’s below the top.
Yes John, I can see that that might work but I would not want to void my warranty. BMW really should seriously consider designing a new front set of heat shields for the M Sport brakes, not only for the Z4 G29 but also for the several other series models where they are fitted. And they should retrospectively fit them to ALL affected models. I think the cost of recalling all the affected cars is what will prevent BMW from carrying this out. Shame on BMW as they are putting profits ahead of the extreme inconvenience that this is causing customers like me and several others that have been affected by this problem. :headbang:

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M40i brakes - design flaw uncovered

Post by Jim S » Tue Jan 05, 2021 10:25 am

Jim S wrote: Tue Jan 05, 2021 10:24 am
john-e89 wrote: Tue Jan 05, 2021 9:58 am
Jim S wrote: Tue Jan 05, 2021 9:52 am

Yes, something fitted over the gap at the top of the heat shield would, most likely, prevent stones from getting in between the front rotors and heat shield. However, the gap between the shield and the wheel rim is very small so I think it would require a different shield design.
I was thinking of attaching it to the inside of the shield Jim, thus not making it any higher then the top of the shield, in fact a good few mm’s below the top.
Yes John, I can see that that might work but I would not want to void my warranty. BMW really should seriously consider designing a new front set of heat shields for the M Sport brakes, not only for the Z4 G29 but also for the several other series models where they are fitted. And they should retrospectively fit them to ALL affected models. I think the cost of recalling all the affected cars is what will prevent BMW from carrying this out. Shame on BMW as they are putting profits ahead of the extreme inconvenience that this is causing customers like me and several others who have been affected by this problem. :headbang:
Current: 2019 Z4 M40i (G29)
Previous BMW's (all new):
2017 520d MSport xDrive (G30)
2016 Z4 20i sDrive SE (E89)
2014 428i MSport Gran Coupe (F36)
2009 530d SE Gran Turismo (F07)
2007 525d SE (E60 LCI)
2005 523i SE (E60)
2002 320d SE (E46)
1982 520i (E28)

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M40i brakes - design flaw uncovered

Post by climbbike » Wed Jan 06, 2021 1:21 am

Has anyone looked at recently released models to see if BMW has changed anything? I just purchased a 2020 so I don't know if anything has changed on the latest cars produced. Hard to believe BMW would not fix it for new cars being made even if they don't want to retrofit older cars. My thought is the new part number could probably be ordered and retrofitted to the older cars.

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M40i brakes - design flaw uncovered

Post by john-e89 » Wed Jan 06, 2021 9:14 am

climbbike wrote: Wed Jan 06, 2021 1:21 am Has anyone looked at recently released models to see if BMW has changed anything? I just purchased a 2020 so I don't know if anything has changed on the latest cars produced. Hard to believe BMW would not fix it for new cars being made even if they don't want to retrofit older cars. My thought is the new part number could probably be ordered and retrofitted to the older cars.
I guess it would depend on how many complaints they have had since launch wether there’s been a change on new cars...

.....I’ll have a look and let you know after 1st March..... :wink:

Hope you enjoy the forum climbbike.... :thumbsup: :driving:
M roady...OEM CSL’s, strut brace, Remus back boxes, ZHP, Intravee.
MR2 MK 2
E89 35i project car...mapped 365bhp, M4 stoppers & wheels, KWV3’s, H&R front ARB, M3 front arms, strut brace, Eisenmann cat back race exhaust, VRSF downpipes inbound.

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M40i brakes - design flaw uncovered

Post by Robsterrob » Wed Jan 13, 2021 11:11 am

I had the dreaded trapped stone the other day - was trying to get out the door for my shift to start, so I had to abort and take my wife's car. That evening, I tried for ages doing forward and reverse, getting increasing frustrated at the horrendous noise. Gave up, and reversed onto the drive ready to call BMW assist, and the stone dropped out!

They really need to sort this.

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