M40i brakes - design flaw uncovered

[craig3.2]

Unfortunately the dealer cannot offer a solution without the approval of BMW and it appears that they are not willing to do anything about it due to the high cost of retrofitting the redesigned parts to all of the affected cars. It is not only the G29 that is affected, the G20 and possibly some other models have the same set up. :thumbsdown:

I have tried my very best to raise the issue with both BMW UK and BMW AG, without success.
Shame on BMW :thumbsdown:

That's majorly disappointing on BMW's part.
They really should be doing better.

They rarely admit things though, likewise other manufacturers,unless they really have to.
LikeVW in the diesel scandal,lol.

 

[BrianD]

I've had my zed since beginning of September, and I have just had my first stone jam :x . What a horrendous noise it makes, luckily I managed to clear it by reversing back and forward so no damage. What suprised me the most was that I wasn't going fast, only doing about 25mph at the time!

 

[Jim S]

I've had my zed since beginning of September, and I have just had my first stone jam :x . What a horrendous noise it makes, luckily I managed to clear it by reversing back and forward so no damage. What suprised me the most was that I wasn't going fast, only doing about 25mph at the time!

My theory is that the stone gets onto the inside of the wheel rim and stays there, by centrifugal force, until the car slows at which time the stone drops down into the large gap between the brake disc and heat shield. This would explain why it only occurs when going slow. :thumbsdown:

 

[climbbike]

I test drove a Z4 M40i yesterday and this happened to me during the test drive. I pulled over to make sure the wheel wasn't falling off but figured it was a rock. When I looked at the heat shield, I thought the rock had got jammed and malformed it. What a horrible design. Looks like someone pounded it out with a sledge hammer. I checked the other side of the car though and it was the exact same so figured that is just how it is. Eventually I backed up and it did come out. Figured it was a 1 in a million chance of happening thing. After reading this, I guess it may happen to me again, since I bought the car!

 

[john-e89]

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. :?

 

[Jim S]

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.
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.

 

[Jim S]

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.

 

[john-e89]

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.

 

[Jim S]

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.

 

[Jim S]

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.

 

[climbbike]

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.

 

[john-e89]

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....

 

[Robsterrob]

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.

 

[Ledg]

I don’t know if one of you guys has a blue z4 from dunholme but it came past where I am working and it clearly had a stone in the front brakes. The noise was horrible. Glad I’ve not had that yet.

 

[ronk]

I don’t know if one of you guys has a blue z4 from dunholme but it came past where I am working and it clearly had a stone in the front brakes. The noise was horrible. Glad I’ve not had that yet.

Give it a little time :thumbsdown:

 

[Jim S]

Took the car out today for a drive now that the weather has improved. Got another stone trapped in the driver side front M Sport brakes (6th time). Really annoying. Stone came out after about a mile of driving. :thumbsdown:

 

[TheGingerOneNI]

Is this also an issue with the Supra? If not is there a different heat shield on them?

 

[Jim S]

Is this also an issue with the Supra? If not is there a different heat shield on them?

I have not heard that the Supra has the same problem. As far as I am aware it is only BMW and Mini that is affected, as the M Sport brakes in these models all use the same design of heat shield.

 

[craig3.2]

Is this also an issue with the Supra? If not is there a different heat shield on them?

I have not heard that the Supra has the same problem. As far as I am aware it is only BMW and Mini that is affected, as the M Sport brakes in these models all use the same design of heat shield.

Terribly poor design on BMW's behalf.
Even worse when they don't own upto it,but then manufacturers often don't

Looks like someone will have to design a modified, aftermarket solution,by way of a heat shield that curves over at the top,and closing the gap,as well as one that has a cut away section in the bottom,where it would touch the track rod end,the cut out would then allow it to curve away from the disc, allowing any stones still getting in,to pass through.

You wouldn't think it would be too difficult for BMW to sort.

 

[Smartbear]

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.

If you modified the disc shield i don’t think it would nullify the warranty for any other part of the car apart from the shield.
If the exhaust fell off for example, it would still be covered.
Rob