M40i brakes - design flaw uncovered

[Flyingfifer]

This is insane!

The idea to switch the sides is a good one but it wont work (the bolt holes arent square) this seems to be nothing more than a glaring design flaw :thumbsdown:

The idea that the stones are sitting on the rim and falling when the car slows seems probable and would make sense, this is only going to be fixed with a redesigned shield which means all the current cars being pulled in for replacements.

 

[TomK]

Is it the rears or the fronts you are having issues with, I'm confused from the 2 posts above?

 

[Jim S]

This is insane!

The idea to switch the sides is a good one but it wont work (the bolt holes arent square) this seems to be nothing more than a glaring design flaw :

The idea that the stones are sitting on the rim and falling when the car slows seems probable and would make sense, this is only going to be fixed with a redesigned shield which means all the current cars being pulled in for replacements.

I couldn't agree more with you Flyingfifer. I am really laying it on thick with BMW to try to get the matter resolved ASAP. It is looking like it will need new redesigned shields having to be fitted front and rear to all the affected cars. I just need more owners who are having the same problem to come forward and make a complaint to their Dealer. I know of four, including myself, at the moment.
:thumbsdown:

 

[Jim S]

Is it the rears or the fronts you are having issues with, I'm confused from the 2 posts above?

It looks like the problem affects both front and rear brakes. The front is more prone to collecting stones due to the shield design curving outwards creating a large gap which is a magnet for stones falling in from above.

 

[TomK]

Well if it is the rears, as it seems to be from that email from bmw then it's a well known issue on those brakes assuming they are the same/similar to f8x f2x f3x m flavours, have a look around the internet.

 

[Nictrix]

The idea that the stones are sitting on the rim and falling when the car slows seems probable and would make sense, this is only going to be fixed with a redesigned shield which means all the current cars being pulled in for replacements.

Would this not possibly mean that there is a design flaw in the design of the wheel and not the disc guard?
I cant remember ever stopping anywhere and there being a pile of stones sitting at the bottom of the wheel.
This can only mean that if the stones are circulating inside the wheel and then falling into the gap when slowing other wheels must be designed that stones are thrown out while driving and don't get the chance to drop into any gaps.

 

[Jim S]

The idea that the stones are sitting on the rim and falling when the car slows seems probable and would make sense, this is only going to be fixed with a redesigned shield which means all the current cars being pulled in for replacements.

Would this not possibly mean that there is a design flaw in the design of the wheel and not the disc guard?
I cant remember ever stopping anywhere and there being a pile of stones sitting at the bottom of the wheel.
This can only mean that if the stones are circulating inside the wheel and then falling into the gap when slowing other wheels must be designed that stones are thrown out while driving and don't get the chance to drop into any gaps.

Thanks for your input Nictrix.
I think the problem lies with the shields not bending over the top of the rotor disc to close off the gap between the shield and rotor disc. All the other cars that I have owned have this and this why they don't have this problem. The shields on the M40i don't cover the gap and are creating a magnet for stones getting into the space between the shield and disc rotor.
:thumbsdown:

 

[Nictrix]

The idea that the stones are sitting on the rim and falling when the car slows seems probable and would make sense, this is only going to be fixed with a redesigned shield which means all the current cars being pulled in for replacements.

Would this not possibly mean that there is a design flaw in the design of the wheel and not the disc guard?
I cant remember ever stopping anywhere and there being a pile of stones sitting at the bottom of the wheel.
This can only mean that if the stones are circulating inside the wheel and then falling into the gap when slowing other wheels must be designed that stones are thrown out while driving and don't get the chance to drop into any gaps.

Thanks for your input Nictrix.
I think the problem lies with the shields not bending over the top of the rotor disc to close off the gap between the shield and rotor disc. All the other cars that I have owned have this and this why they don't have this problem. The shields on the M40i don't cover the gap and are creating a magnet for stones getting into the space between the shield and disc rotor.
:thumbsdown:

Off the top of my head the only car I have had that the shield covers the disc is the E89 rear brakes.
The front disc shield on the E89 doesn't cover the disc.

 

[Jim S]

Would this not possibly mean that there is a design flaw in the design of the wheel and not the disc guard?
I cant remember ever stopping anywhere and there being a pile of stones sitting at the bottom of the wheel.
This can only mean that if the stones are circulating inside the wheel and then falling into the gap when slowing other wheels must be designed that stones are thrown out while driving and don't get the chance to drop into any gaps.

Thanks for your input Nictrix.
I think the problem lies with the shields not bending over the top of the rotor disc to close off the gap between the shield and rotor disc. All the other cars that I have owned have this and this why they don't have this problem. The shields on the M40i don't cover the gap and are creating a magnet for stones getting into the space between the shield and disc rotor.
:thumbsdown:

Off the top of my head the only car I have had that the shield covers the disc is the E89 rear brakes.
The front disc shield on the E89 doesn't cover the disc.

It is just the gap that the shield covers, not the whole disc.

 

[Nictrix]

Thanks for your input Nictrix.
I think the problem lies with the shields not bending over the top of the rotor disc to close off the gap between the shield and rotor disc. All the other cars that I have owned have this and this why they don't have this problem. The shields on the M40i don't cover the gap and are creating a magnet for stones getting into the space between the shield and disc rotor.
:thumbsdown:

Off the top of my head the only car I have had that the shield covers the disc is the E89 rear brakes.
The front disc shield on the E89 doesn't cover the disc.

It is just the gap that the shield covers, not the whole disc.

Yeah thats what I mean. Most are either flat or curve slightly away from the disc except the rear of the E89 which slightly covers the outer edge.

 

[Flyingfifer]

Off the top of my head the only car I have had that the shield covers the disc is the E89 rear brakes.
The front disc shield on the E89 doesn't cover the disc.

It is just the gap that the shield covers, not the whole disc.

Yeah thats what I mean. Most are either flat or curve slightly away from the disc except the rear of the E89 which slightly covers the outer edge.

Looking at the E86 one it curves towards the disc as well
https://cdn11.bigcommerce.com/s-dals72eswg/images/stencil/500x659/products/5860/47539/$_57__07771.1515805900.JPG?c=2
https://cdn4.pelicanparts.com/techarticles/BMW_Z4M/91-BRAKES-Brake_Rotor_Replacement/images_large/pic01.jpg

 

[Nictrix]

It is just the gap that the shield covers, not the whole disc.

Yeah thats what I mean. Most are either flat or curve slightly away from the disc except the rear of the E89 which slightly covers the outer edge.

Looking at the E86 one it curves towards the disc as well
https://cdn11.bigcommerce.com/s-dals72eswg/images/stencil/500x659/products/5860/47539/$_57__07771.1515805900.JPG?c=2
https://cdn4.pelicanparts.com/techarticles/BMW_Z4M/91-BRAKES-Brake_Rotor_Replacement/images_large/pic01.jpg

Yeah that's pretty much the same as the rears on the E89. Both those pics are rears also.

 

[flybobbie]

Probably designed by someone that did realise what the lip was for on the original design.
I always call it reinventing the kettle spout.

Bit like the caravan i owned, the version i bought they moved the water heater the furthest they could from the shower and sink, so the water froze in the pipes in winter.
Previous versions the heater was next to the shower and sink.
2 years in that van i think i could design caravans better than the company making them for 50 years.

 

[Jim S]

My dealer sent me the latest response received from BMW UK regarding the problem with stones getting into the M Sport brakes on my M40i. I am taking the car in for the requested inspection tomorrow.

"BMW UK Technical have replied to the further information we sent them this morning. To paraphrase, as the vehicle is a new model, there will be some feedback generated to AG, however they do not expect a solution introduced to prevent stones from being picked up by the wheels. They would like us to confirm the brake components fitted to the car are correct and to check the brake shields, even though they believe they cannot be fitted incorrectly. Is there a possibility the car could be made available for us to check the parts fitted are correct and we can reply to the Technical case? This will give us an opportunity to take some images and measurements that they requested in their initial reply.

it is worth pointing out there have been no other issues of this nature reported to BMW UK, other than your own. We copied and pasted your entire email to the technical case, so they are aware of all your comments."

 

[Flyingfifer]

...

Id ask about returning the car

 

[Jim S]

...

Id ask about returning the car

I do like the car otherwise if they could fix the problem with the brakes I would be happy. In any case it would cost me a lot of money to take it back.

 

[Jim S]

This photo of the front M Sport brake assembly clearly shows what the problem is. The wide open top is a magnet for catching stones and the bottom of the shield bends in towards the disc closing the gap and trapping the stone. The bottom of the shield can't be bent outwards because of the track rod end which is right up against the shield.

 

[Jim S]

And here's the rear brake assembly. Better than the front but not great. Needs the top of the shield to bend over to close the gap between the shield and the disc rotor.

 

[flybobbie]

I wonder if a edging rubber with a lip could be fitted.
This sort of rubber.
https://www.ebay.co.uk/itm/Leaf-Fin-Seal-Rubber-Extrusion-Edge-Trim-26mm-x-21mm/113245997048?hash=item1a5dfcc7f8:g:KBoAAOSwj4dbmVlR
https://www.ebay.co.uk/itm/Large-Vertical-Shark-Fin-Car-Seal-Rubber-EDGE-TRIM-Van-Boat-Truck-Caravan/122843171768?_trkparms=aid%3D555018%26algo%3DPL.SIM%26ao%3D1%26asc%3D58648%26meid%3D22e542ed8cdb49818269fe0b62570fac%26pid%3D100005%26rk%3D4%26rkt%3D12%26mehot%3Dpp%26sd%3D113245997048%26itm%3D122843171768&_trksid=p2047675.c100005.m1851
https://www.ebay.co.uk/itm/Large-Exposed-Fin-Car-Rubber-EDGE-TRIM-SEAL-Boat-Caravan-Door-Bonnet-Boot/223007520740?_trkparms=aid%3D555018%26algo%3DPL.SIM%26ao%3D1%26asc%3D58648%26meid%3D2d1a995e1af5498ab129c52c1e16ca2c%26pid%3D100008%26rk%3D5%26rkt%3D12%26sd%3D122843171768%26itm%3D223007520740&_trksid=p2047675.c100008.m2219

 

[Ewazix]

Has some top things you need to know as an M driver including about stones in the dust shield

Looks like the FX8 ones curve over as normal.
https://youtu.be/rgVLBT0HWWE?t=57