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      06-10-2019, 01:06 PM   #45
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Quote:
Originally Posted by DPelletier View Post
Agreed.

There is no reason to believe that the OP's stated issue/concern is a function of all high performance braking systems; there are many other cars with high performance brakes that don't seem to have a problem trapping rocks between the rotor and dust shield. My Jaguar has their "superperformance brakes" and there haven't been any reported issues with stone trapment in the past 4 years that I've been a member of that forum...



2 cents,
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Agree as well. This isn’t a ‘it’s so low I can’t get up my driveway without scratching sound from the skirt below the front fender’ or ‘engine is loud’ type of complaint. Or visibility with the roof up is poor complaint. All of these are in the ‘well, what did you expect’ category GruessGott is mentioning. But stones in the break system isn’t in that what did you expect category.

Nor would I consider not having stones stuck in the breaking system a ‘luxury’ or ‘comfort’ feature.
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      06-10-2019, 01:31 PM   #46
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Originally Posted by CeEl View Post
Agree as well. This isn’t a ‘it’s so low I can’t get up my driveway without scratching sound from the skirt below the front fender’ or ‘engine is loud’ type of complaint. Or visibility with the roof up is poor complaint. All of these are in the ‘well, what did you expect’ category GruessGott is mentioning. But stones in the break system isn’t in that what did you expect category.

Nor would I consider not having stones stuck in the breaking system a ‘luxury’ or ‘comfort’ feature.
Well said. I totally agree as well.
It is not only the Z4 M40i that is affected. In the UK the same brakes are fitted to the 20i and 30i MSport variants of the G29 Z4. Furthermore, my local BMW Service Manager tells me that identical brakes are also fitted to the MSport Plus variants of the new G20 3 Series 318d, 320d, 320i and 330i as well as the M340i. Other than the M340i, I would not call any of these cars performance cars, they are regular road cars. Owners of these cars are very likely to experience the same issue. Only time will tell.

Last edited by Jim S; 06-11-2019 at 02:38 AM..
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      06-10-2019, 01:46 PM   #47
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Originally Posted by sanfordrich View Post
I'm no expert, but that seems like a huge difference compared to the front brakes. Most stones would simply fall through (if I'm looking at the photo correctly) where with the front brakes they wouldn't.
Yes, I think the problem is more likely to occur on the front brakes. The rear ones are likely to let most of the stones pass through.
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      06-10-2019, 10:29 PM   #48
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Originally Posted by SgtGigglebox View Post
People have been complaining about this on some of the M cars for years. Doesn't appear that they have any interest in addressing it.
Not completely true. The part that is true is that has been a problem on the F8x M2/M3/M4 since the beginning. I experienced this while in Italy when I took Euro Delivery of my 2016 M4. It freaked me out when it happened and I immediately pulled off the road thinking that something was wrong. It sounded like I was pulling a string of tin cans behind the car. By the time I stopped I remembered reading about this and that there was no cause for alarm. The rock(s) apparently fell out while I was stopped because the noise went away.

There are lots of posts about this in the F80 forum. Some people have indicated that BMW did in fact release a revised part that is supposed to remedy the problem. My wife's 2018 M3 has not experienced this problem in almost a year.

The easiest and fastest fix is to pull off the rear wheels and just push the backing plate inwards towards the diff. I did this while fitting track pads in Switzerland, after the Italy part of the trip and before Nurburgring. The problem didn't recur again during Euro Delivery or in the three years since.

On the M2/M3/M4 this occurs primarily on the rear.
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      06-11-2019, 10:26 AM   #49
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Quote:
Originally Posted by SD ///M4 View Post
The easiest and fastest fix is to pull off the rear wheels and just push the backing plate inwards towards the diff.
Awesome! I'll just add a lightweight floor jack, 17mm socket, breaker bar, and torque wrench to my list of items to carry around in the trunk.



But in all seriousness, it sounds like having a wooden dowel rod that can be inserted through the wheel spokes, and used to move the backing plate might make more sense. At least that's small, light and easy to hide inside the area where the battery is located.
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      06-11-2019, 11:50 AM   #50
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Quote:
Originally Posted by CeEl View Post
All of these are in the ‘well, what did you expect’ category GruessGott is mentioning.
Guys, my point from an engineer who's designed stuff and reacted to design updates in fleet operations: you're always balancing costs, core design priorities, secondary priorities, financial impact, and legal impact against impact to the user.

In this case

(1.) BMW engineering has designed a great brake (at least on all of my cars) that, yes, has this rocks downside whether you expected it or not

(2.) My assumption is they've researched a fix
and weighed that fix against many factors including severity of impact to the user - the result of the analysis was, keep it as is.

We can quibble whether #2 is a bad assumption ...

Maybe BMW has completely ignored this issue, but that'd be surprising given the volume of noise - much more likely is they researched a fix and decided a legally / technically / financially appropriate fix would be more trouble than it's worth given the impact.

For me, it wouldn't even be worth a drive to the dealer over and frankly I don't want them touching shit on my car, so even if there was one I'd skip it.

Thus, this is 100% a comfort vs performance issue in that we have high performance brakes which have some comfort downsides because no design is perfect (and you didn't pay for perfect, you paid for performance and you get that).

If you buy performance brakes (and you did), you should expect them to perform - if they do, the contract is fulfilled.

If you want perfection, that's what aftermarket is for.
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      06-11-2019, 12:09 PM   #51
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Me: Hires plumber to install new toilet

Plumber: Adjusts process and parts slightly to save money, and make the job slightly easier.

Me: Why does my toilet make that horrendous sound when I flush it? That doesn't sound right.

Plumber: Does it flush?

Me: Well yeah.

Plumber: Ok then. [leaves]

----------------------------

Business always balance the factors that you cited, but it doesnt mean that they arent weighing those factors in a way that aligns more to the financial & legal end of the spectrum and not customer satisfaction. Different people are more or less pickier with the product or service that they pay for. The folks on this thread are less accepting of what is perceived to be a flaw in a product than you. That doesnt make you or them wrong - just different, but it also doesnt change the fact that something is, on face value, not normal with a type of product.
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      06-11-2019, 01:37 PM   #52
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Quote:
Originally Posted by GrussGott View Post
Guys, my point from an engineer who's designed stuff and reacted to design updates in fleet operations: you're always balancing costs, core design priorities, secondary priorities, financial impact, and legal impact against impact to the user.

In this case

(1.) BMW engineering has designed a great brake (at least on all of my cars) that, yes, has this rocks downside whether you expected it or not

(2.) My assumption is they've researched a fix
and weighed that fix against many factors including severity of impact to the user - the result of the analysis was, keep it as is.

We can quibble whether #2 is a bad assumption ...

Maybe BMW has completely ignored this issue, but that'd be surprising given the volume of noise - much more likely is they researched a fix and decided a legally / technically / financially appropriate fix would be more trouble than it's worth given the impact.

For me, it wouldn't even be worth a drive to the dealer over and frankly I don't want them touching shit on my car, so even if there was one I'd skip it.

Thus, this is 100% a comfort vs performance issue in that we have high performance brakes which have some comfort downsides because no design is perfect (and you didn't pay for perfect, you paid for performance and you get that).

If you buy performance brakes (and you did), you should expect them to perform - if they do, the contract is fulfilled.

If you want perfection, that's what aftermarket is for.
It's your assumption that in order to have "great brakes" you need the dust shield to trap and hold rocks that is the flaw in your logic IMO.

Do I think this is a huge deal in the big scheme of things? No, I don't....but I do think that it sounds like this dust shield design is poor one for a vehicle not strictly limited to track use.

Depending on the frequency of any occurances, I'd likely just deal with it myself.....a lift makes things pretty easy in that regard.

2 cents,


Dave
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      06-11-2019, 01:47 PM   #53
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Quote:
Originally Posted by GrussGott View Post

Thus, this is 100% a comfort vs performance issue in that we have high performance brakes which have some comfort downsides because no design is perfect (and you didn't pay for perfect, you paid for performance and you get that).

If you buy performance brakes (and you did), you should expect them to perform - if they do, the contract is fulfilled.
You are entitled to your opinion and are clearly willing to trade off the flaws in the brakes design for performance. I am not willing to accept a design flaw that is causing me severe inconvenience as the brakes are absolutely not performing as they should and therefore are not fit for purpose. Here is my story so far:-

Stones got trapped in my brakes four times in the first three weeks of ownership. I tried the recommended forward and back movements, slow, fast, brake hard etc. The stone stayed put each time. Twice I drove a few miles and the stone came out. Twice, after driving several miles with the brakes squealing like a banshee I had to take the car to my dealer as the stone would not come out. The dealer had to put the car on the ramp and take the wheel off to dislodge the stone, which was well and truly stuck between the shield and the rotor on the front wheel. No way was it coming out on its own accord until it had either disintegrated or damaged the rotor to the extent that it found a way out.

For me, brakes performance is not just about the brakes stopping you efficiently and safely. They also need to perform correctly under normal day to day driving conditions and, evidently, my brakes fail in that respect.

Finally, from what other M car owners have been saying, I understand that the problem they were having related to the rear brakes and BMW came out with a fix for that. My problem relates to the front brakes and may actually be a completely different and new problem.

Last edited by Jim S; 06-12-2019 at 03:36 AM..
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      06-11-2019, 02:17 PM   #54
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Quote:
Originally Posted by PrionFawkes View Post
Awesome! I'll just add a lightweight floor jack, 17mm socket, breaker bar, and torque wrench to my list of items to carry around in the trunk.



But in all seriousness, it sounds like having a wooden dowel rod that can be inserted through the wheel spokes, and used to move the backing plate might make more sense. At least that's small, light and easy to hide inside the area where the battery is located.
I guess that I should have been more specific; I only had to bend the backing plate back once, it's not like I have to do this every time it happens, and it didn't happen again. You push on the backing plate to bend it back and increase the distance between the backing plate and the rotor. Once the backing plate is bent back, at least on the F8x cars, the problem goes away. This is what worked for me.

It does appear that the backing plate on the G29 brakes are designed differently, and the problem is not with the rear brakes but with the front brakes. Everyone with a G29 that experiences this problem should complain to their dealer and BMW may redesign the backing plate and retrofit them to cars that experience the problem.
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      06-11-2019, 02:24 PM   #55
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Quote:
Originally Posted by SD ///M4 View Post

It does appear that the backing plate on the G29 brakes are designed differently, and the problem is not with the rear brakes but with the front brakes. Everyone with a G29 that experiences this problem should complain to their dealer and BMW may redesign the backing plate and retrofit them to cars that experience the problem.
Absolutely, the rear brakes may be alright but the front brakes need a redesign and retrofit by BMW.
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      06-11-2019, 02:56 PM   #56
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Originally Posted by Jim S View Post
You are entitled to your opinion and are clearly willing to trade off the flaws in the brakes design for performance.
Well, i'd more say my core expectation of a performance vehicle is performance; and that I also expect niggles because mechanical stuff.

You may well be right, there could be a design issue here. Or not. It could be a quality control issue, or it could be a cost trade off. Or who knows? Not us, we don't know.

So my point is, before we puff up with self-righteous indignation and all-knowing presumptions, we should find out what's going on, give BMW the benefit of time to research, and see what they say.

If it is as you say, I'm expecting BMW to make it right.
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      06-11-2019, 03:01 PM   #57
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Quote:
Originally Posted by GrussGott View Post
Well, i'd more say my core expectation of a performance vehicle is performance; and that I also expect niggles because mechanical stuff.

You may well be right, there could be a design issue here. Or not. It could be a quality control issue, or it could be a cost trade off. Or who knows? Not us, we don't know.

So my point is, before we puff up with self-righteous indignation and all-knowing presumptions, we should find out what's going on, give BMW the benefit of time to research, and see what they say.

If it is as you say, I'm expecting BMW to make it right.
Yes, I have already taken the case to BMW via my dealer who has examined the brakes, taken measurements and sent a video to BMW for review.

Last edited by Jim S; 06-12-2019 at 03:39 AM..
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      06-25-2019, 07:56 PM   #58
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Quote:
Originally Posted by Jim S View Post
Absolutely, the rear brakes may be alright but the front brakes need a redesign and retrofit by BMW.
You keep saying that there is something wrong with your brakes. There is nothing wrong with your brakes. They work just fine. The brakes don't need a redesign. Maybe the backing plate for the rotors does - maybe - but backing plates are not brakes. In fact, backing plates serve no function in stopping your car.
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      06-25-2019, 08:05 PM   #59
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You are splitting hairs here SakhirM4. The shields are part of the design of the brakes and are faulty, certainly on the front brakes. The shields need to be redesigned as they are currently a magnet for stones.
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      06-25-2019, 08:20 PM   #60
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Originally Posted by Jim S View Post
You are splitting hairs here SakhirM4. The shields are part of the design of the brakes and are faulty, certainly on the front brakes. The shields need to be redesigned as they are currently a magnet for stones.
Not splitting hairs, just being accurate. I had a stone stuck in my M4 front brake once and it sounded terrible, but there was nothing wrong with my brakes. Fortunately, in 5 years on ownership of the M4, it has never happened again. The shields are about as much a function of your brakes as the hood (bonnet) is to the function of your motor.
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      06-25-2019, 08:36 PM   #61
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No you are far from being accurate. The shields are an important part of the brakes in relation to performance. They are designed to divert the flow of air over the brake rotors to keep them from overheating and fading. They are also designed to prevent unwanted heat from transferring to the brake hoses and other heat sensitive parts of the car.
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      06-25-2019, 09:12 PM   #62
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Originally Posted by Jim S View Post
No you are far from being accurate. The shields are an important part of the brakes in relation to performance. They are designed to divert the flow of air over the brake rotors to keep them from overheating and fading. They are also designed to prevent unwanted heat from transferring to the brake hoses and other heat sensitive parts of the car.
Yes, I am being accurate. They do not increase cooling. They do not affect brake performance at all. Their purpose is to do what you stated last - "prevent unwanted heat from transferring to the brake hoses and other heat sensitive parts of the car" (such as rubber suspension bushings). Nothing to do with brake performance.
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      06-26-2019, 07:54 AM   #63
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I don't really understand the pedantic rabbit hole this discussion has descended into. Quite frankly I don't give a sh%t what purpose the brake disc shields provide, and I honestly don't care what anyone's opinion regarding them is.

The facts are:
  • A G29 Z4 owner has experienced an issue with rocks getting stuck between the rotor and the shield.
  • This has occurred on multiple occasions.
  • Other forum members have experienced the same issue.
  • A case has been submitted to BMW for review.
  • The OP has asked, that anyone experiencing this issue, to report it to their service center as well.
  • This thread is intended to track the status of this issue [if it occurs to more owners] and any possible remedies provided by BMW.

That's it.
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      07-10-2019, 07:41 AM   #64
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Update on the stones in M Sport brakes problem on the Z4 G29.

My dealer tells me that following the report and video that he sent over to BMW AG for review. Their response is that it is unlikely that the design of the shields will be carried out as they have not received sufficient complaints from owners to justify this.

Very disappointing response from BMW.
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      07-10-2019, 10:41 AM   #65
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Originally Posted by Jim S View Post
Update on the stones in M Sport brakes problem on the Z4 G29.

My dealer tells me that following the report and video that he sent over to BMW AG for review. Their response is that it is unlikely that the design of the shields will be carried out as they have not received sufficient complaints from owners to justify this.

Very disappointing response from BMW.
I have yet to experience it. If I do I will certainly complain about it.
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      07-10-2019, 11:42 AM   #66
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I have yet to experience it. If I do I will certainly complain about it.
Maybe you don't drive on unimproved gravel roads.
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