BMW Garage BMW Meets Register Search Today's Posts Mark Forums Read
BMW Z4 Forums (G29) BMW Z4 (G29) General Forum Z4 M40i Design Flaw Uncovered

Post Reply
 
Thread Tools Search this Thread
      06-05-2019, 05:40 AM   #23
Jim S
Member
Jim S's Avatar
Scotland
216
Rep
188
Posts

Drives: Z4 M40i G29
Join Date: May 2017
Location: Scotland

iTrader: (0)

Garage List
Quote:
Originally Posted by CeEl View Post
This isn't a Z4 only problem... other cars with the M brakes have the same issue.

For what it's worth: only happened to me once so far.

I am disappointed in BMW saying they never heard about this... well, maybe not on the US M40i since it is so new... where is ABC News when you need them?
Yes, it does need other owners to speak up and register a complaint with their BMW Dealer in order to get BMW to take appropriate action.

In the UK we have a TV program called "Watchdog" who take on cases like this and air it to millions of viewers. The way things are going I may be approaching them for some help. I'm sure BMW would not like that.
Appreciate 0
      06-05-2019, 05:43 AM   #24
Jim S
Member
Jim S's Avatar
Scotland
216
Rep
188
Posts

Drives: Z4 M40i G29
Join Date: May 2017
Location: Scotland

iTrader: (0)

Garage List
Quote:
Originally Posted by DPelletier View Post
I'll have to take a look when I get the car; I have a metal fab shop so I'm sure I could modify the shields if need be.......the hoist helps too. Or I could just take them off; I'm not convinced they do anything useful anyhow - never seen them on a track car or racecar or any of my 41 motorcycles.

Dave
Yes Dave, I agree that it needs redesigned shields front and back to fix the problem.
Appreciate 0
      06-06-2019, 08:02 AM   #25
Jim S
Member
Jim S's Avatar
Scotland
216
Rep
188
Posts

Drives: Z4 M40i G29
Join Date: May 2017
Location: Scotland

iTrader: (0)

Garage List
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.
Attached Images
 
Appreciate 2
      06-06-2019, 08:57 AM   #26
PrionFawkes
Private
71
Rep
75
Posts

Drives: G29 Z4 M40i (2020)
Join Date: Sep 2018
Location: Chattanooga, TN

iTrader: (0)

I'm not an automotive engineer, but as hobby I often fix and correct issues they've caused on my project cars. So I tend to give them the benefit of the doubt, until it's been proven they've designed a defect that needs addressing.

That being said, the photo above creates several questions and concerns for me. Why is the gap so large between the rotor and shielding? Why does the shield flare out at the top, but in at that bottom (I understand the steering rod clearance issue)?

I know I'm probably wrong, but it almost looks like that thing is installed upside down and backwards.

Why doesn't it follow the most prevalent design style for this component? See my examples below:
Attached Images
  
Appreciate 1
Jim S215.50

      06-06-2019, 10:07 AM   #27
tmehanna
Private
21
Rep
79
Posts

Drives: 528i f10
Join Date: Aug 2012
Location: Egypt

iTrader: (0)

Quote:
Originally Posted by Jim S View Post
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.
I am shocked at the design!
Appreciate 0
      06-06-2019, 10:08 AM   #28
Jim S
Member
Jim S's Avatar
Scotland
216
Rep
188
Posts

Drives: Z4 M40i G29
Join Date: May 2017
Location: Scotland

iTrader: (0)

Garage List
Quote:
Originally Posted by PrionFawkes View Post
I'm not an automotive engineer, but as hobby I often fix and correct issues they've caused on my project cars. So I tend to give them the benefit of the doubt, until it's been proven they've designed a defect that needs addressing.

That being said, the photo above creates several questions and concerns for me. Why is the gap so large between the rotor and shielding? Why does the shield flare out at the top, but in at that bottom (I understand the steering rod clearance issue)?

I know I'm probably wrong, but it almost looks like that thing is installed upside down and backwards.

Why doesn't it follow the most prevalent design style for this component? See my examples below:
Yes, it clearly is a design flaw on these brakes. The dealer says it is probably designed that way to allow cooling air to flow across the disc. It is obvious to me that whoever designed the shield gave no thought to stones easily getting in due to the wide opening at the top. If the bottom had been opened up as well there is a good chance that the stones would drop right through onto the road. Clearly it is a fault and requires a complete redesign of the brake shields to fix the problem.

I am informed that the new 3 series M Sport brakes are exactly the same design. That car is a big seller so I'm sure it will only be a matter of time until many other owners start to complain as well. Let's wait and see what happens.
Appreciate 0
      06-06-2019, 10:19 AM   #29
Jim S
Member
Jim S's Avatar
Scotland
216
Rep
188
Posts

Drives: Z4 M40i G29
Join Date: May 2017
Location: Scotland

iTrader: (0)

Garage List
And here is a photo of the rear M Sport brakes. Better than the front ones but still not great due to the gap not being closed off at the top like other designs that I have seen.
Attached Images
 
Appreciate 1
      06-06-2019, 04:30 PM   #30
sanfordrich
Enlisted Member
21
Rep
49
Posts

Drives: BMW Z3
Join Date: May 2019
Location: Colorado

iTrader: (0)

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.
Appreciate 0
      06-06-2019, 05:21 PM   #31
Jim S
Member
Jim S's Avatar
Scotland
216
Rep
188
Posts

Drives: Z4 M40i G29
Join Date: May 2017
Location: Scotland

iTrader: (0)

Garage List
Quote:
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, the rear brake assembly design is much better than the front. If the shield had a little bit bent over at the top it would have been perfect. The front ones are a complete disaster. Shame on BMW.
Appreciate 0
      06-07-2019, 11:38 AM   #32
PrionFawkes
Private
71
Rep
75
Posts

Drives: G29 Z4 M40i (2020)
Join Date: Sep 2018
Location: Chattanooga, TN

iTrader: (0)

My Z4 finally reached the stage of delivery (Awaiting Carrier Assignment), where the VIN is active on the BMW Owners site. I'm able to download the Driver's Guide, and immediately found this in the FAQ section.
Attached Images
 
Appreciate 0
      06-07-2019, 11:59 AM   #33
Jim S
Member
Jim S's Avatar
Scotland
216
Rep
188
Posts

Drives: Z4 M40i G29
Join Date: May 2017
Location: Scotland

iTrader: (0)

Garage List
Quote:
Originally Posted by PrionFawkes View Post
My Z4 finally reached the stage of delivery (Awaiting Carrier Assignment), where the VIN is active on the BMW Owners site. I'm able to download the Driver's Guide, and immediately found this in the FAQ section.
I have never seen this statement before and it should not allow BMW to dodge their responsibility. The M Sport front brakes on the Z4 are clearly flawed, not fit for purpose and need to be redesigned ASAP.

Shame on BMW for trying to shirk their responsibilities.

Last edited by Jim S; 06-07-2019 at 12:31 PM..
Appreciate 0
      06-09-2019, 01:26 PM   #34
Mani59
BMW Miniature Collector!
United Kingdom
1147
Rep
6,145
Posts

Drives: F10 530d M Spt & E46 330i Inv
Join Date: Nov 2010
Location: Leicestershire

iTrader: (1)

This happened many times in my E39 5er several years ago. Very annoying!
Had to get Assist out to clear the stones every time!
Appreciate 0
      06-09-2019, 02:22 PM   #35
Jim S
Member
Jim S's Avatar
Scotland
216
Rep
188
Posts

Drives: Z4 M40i G29
Join Date: May 2017
Location: Scotland

iTrader: (0)

Garage List
Quote:
Originally Posted by Mani59 View Post
This happened many times in my E39 5er several years ago. Very annoying!
Had to get Assist out to clear the stones every time!
Never happened to me in any car before this one and I have been driving for more than 50 years.

Next time I will be calling out BMW Assist to remove the stone.
Appreciate 0
      06-09-2019, 04:25 PM   #36
GrussGott
Major General
GrussGott's Avatar
United_States
7495
Rep
6,601
Posts

Drives: 2018 M4
Join Date: Jun 2009
Location: Newport Beach

iTrader: (0)

Garage List
2011 E93 M3  [0.00]
Quote:
Originally Posted by Jim S View Post
I have never seen this statement before and it should not allow BMW to dodge their responsibility. The M Sport front brakes on the Z4 are clearly flawed, not fit for purpose and need to be redesigned ASAP.

Shame on BMW for trying to shirk their responsibilities.
I mean maybe - honestly I've been dealing with this for ~6 years now and eons ago I learned how to fix it with a quick full throttle and a hard brake and that's worked across 3 cars. (afaik, there are other fixes, and some have bent the shield, etc)

This is one of those things there seems to be a legit design reason for, but leads to brake noise like ceramic.

Maybe I've gotten complacent but honestly it's like shifting for me now, I just clear the rock unconsciously, just not that big of a deal.
__________________

Quote:
Originally Posted by mkoesel View Post
I thought the next M4 was going to be a flying car powered by bloomin' onions and a teaspoon of mayonnaise. At least that's what I read on the internet @ BimmerPoop.org.
Appreciate 0
      06-09-2019, 04:26 PM   #37
GrussGott
Major General
GrussGott's Avatar
United_States
7495
Rep
6,601
Posts

Drives: 2018 M4
Join Date: Jun 2009
Location: Newport Beach

iTrader: (0)

Garage List
2011 E93 M3  [0.00]
Quote:
Originally Posted by Jim S View Post
I have never seen this statement before and it should not allow BMW to dodge their responsibility. The M Sport front brakes on the Z4 are clearly flawed, not fit for purpose and need to be redesigned ASAP.

Shame on BMW for trying to shirk their responsibilities.
I mean maybe, sounds a bit unhinged though - honestly I've been dealing with this for ~6 years now and eons ago I learned how to fix it with a quick full throttle and a hard brake and that's worked across 3 cars. (afaik, there are other fixes, and some have bent the shield, etc). It's kind of an excuse for fun!

This is one of those things there seems to be a legit design reason for, but leads to brake noise like ceramic.

Maybe I've gotten complacent but honestly it's like shifting for me now, I just clear the rock unconsciously, just not that big of a deal despite happening frequently.

Designs have trade-offs and this seems like one of them.
__________________

Quote:
Originally Posted by mkoesel View Post
I thought the next M4 was going to be a flying car powered by bloomin' onions and a teaspoon of mayonnaise. At least that's what I read on the internet @ BimmerPoop.org.
Appreciate 0
      06-09-2019, 04:37 PM   #38
Jim S
Member
Jim S's Avatar
Scotland
216
Rep
188
Posts

Drives: Z4 M40i G29
Join Date: May 2017
Location: Scotland

iTrader: (0)

Garage List
Quote:
Originally Posted by GrussGott View Post
I mean maybe, sounds a bit unhinged though - honestly I've been dealing with this for ~6 years now and eons ago I learned how to fix it with a quick full throttle and a hard brake and that's worked across 3 cars. (afaik, there are other fixes, and some have bent the shield, etc). It's kind of an excuse for fun!

This is one of those things there seems to be a legit design reason for, but leads to brake noise like ceramic.

Maybe I've gotten complacent but honestly it's like shifting for me now, I just clear the rock unconsciously, just not that big of a deal despite happening frequently.

Designs have trade-offs and this seems like one of them.
When I spend over £50k on a car I donít expect that kind of problem. Nor am I willing to put up with it.
Appreciate 0
      06-09-2019, 04:46 PM   #39
GrussGott
Major General
GrussGott's Avatar
United_States
7495
Rep
6,601
Posts

Drives: 2018 M4
Join Date: Jun 2009
Location: Newport Beach

iTrader: (0)

Garage List
2011 E93 M3  [0.00]
Quote:
Originally Posted by Jim S View Post
When I spend over £50k on a car I don’t expect that kind of problem. Nor am I willing to put up with it.
I think the point is, you bought a performance car, not a luxo cruiser, so what you're calling a problem may, in fact, be a feature.

Have you had an M car, or any performance car before? Are you aware of these kinds of trade-offs? "it's jerky! the transmission shifts hard! it's loud!"

Maybe you're just finding out you're not a performance car guy and not willing to accept the trade-offs they have. Lord knows BMW continues taking away performance features in favor of luxury these days ...

Performance cars have trade-offs, no shame in moving to Lexus if that's more your jam.
__________________

Quote:
Originally Posted by mkoesel View Post
I thought the next M4 was going to be a flying car powered by bloomin' onions and a teaspoon of mayonnaise. At least that's what I read on the internet @ BimmerPoop.org.
Appreciate 0
      06-09-2019, 05:12 PM   #40
Jim S
Member
Jim S's Avatar
Scotland
216
Rep
188
Posts

Drives: Z4 M40i G29
Join Date: May 2017
Location: Scotland

iTrader: (0)

Garage List
Quote:
Originally Posted by GrussGott View Post
I think the point is, you bought a performance car, not a luxo cruiser, so what you're calling a problem may, in fact, be a feature.

Have you had an M car, or any performance car before? Are you aware of these kinds of trade-offs? "it's jerky! the transmission shifts hard! it's loud!"

Maybe you're just finding out you're not a performance car guy and not willing to accept the trade-offs they have. Lord knows BMW continues taking away performance features in favor of luxury these days ...

Performance cars have trade-offs, no shame in moving to Lexus if that's more your jam.
Iím not going to get into an argument with you. Performance car or not I donít agree with you.
Appreciate 0
      06-09-2019, 06:55 PM   #41
GrussGott
Major General
GrussGott's Avatar
United_States
7495
Rep
6,601
Posts

Drives: 2018 M4
Join Date: Jun 2009
Location: Newport Beach

iTrader: (0)

Garage List
2011 E93 M3  [0.00]
Quote:
Originally Posted by Jim S View Post
I’m not going to get into an argument with you. Performance car or not I don’t agree with you.
This is a discussion forum, and I'm replying to your topic in a thoughtful way, with new ideas, which should encourage a thoughtful reply from you (it didn't) or others.

Your complaint thread prioritizes comfort over performance (I don't hear you complaining about brake fade), despite the fact you decided to buy a performance oriented car, and now you'd like BMW to give you the BMW luxury convertible you didn't decide to buy.

To lay it out more clearly for you:

(1.) Is it reasonable to expect performance oriented cars to have trade-offs of luxury/comfort for performance?

(2.) If yes, should braking be one of those places we could expect those performance-for-luxury trade-offs?

(3.) If yes, are fade-resistant brakes worth the trade off of luxury/comfort in this Z4? If yes, then stop & congrats

(4.) If no, trade for the 2er vert or are you willing to pay more for brakes with high performance and comfort?

(5.) If yes, then aftermarket.

Personally M-performance brakes are a fine trade-off to me, and I can confirm the brakes on my M4 are monsters, and that's my top priority, everything else is gravy. While I'd prefer my brakes not be prone to getting rocks caught, I also understand perfection is impossible and we shouldn't let the perfect be the enemy of the really, really good.

TLDR:
If your complaint of performance brakes is performance, that's reasonable; if your complaint of performance brakes is comfort, that's not reasonable.


And, yes, I do understand you believe perfection is reasonable for the price you've paid.
__________________

Quote:
Originally Posted by mkoesel View Post
I thought the next M4 was going to be a flying car powered by bloomin' onions and a teaspoon of mayonnaise. At least that's what I read on the internet @ BimmerPoop.org.

Last edited by GrussGott; 06-09-2019 at 07:03 PM..
Appreciate 0
      06-09-2019, 10:22 PM   #42
SgtGigglebox
Lieutenant
SgtGigglebox's Avatar
United_States
62
Rep
492
Posts

Drives: '13 Atacama 35is
Join Date: Sep 2012
Location: Washington D.C. Area

iTrader: (0)

Quote:
Originally Posted by GrussGott View Post
TLDR:
If your complaint of performance brakes is performance, that's reasonable; if your complaint of performance brakes is comfort, that's not reasonable.


And, yes, I do understand you believe perfection is reasonable for the price you've paid.
I think the mistake here is framing a design flaw that routinely captures stones in a position where they are forcibly ground against the internals of the braking system as something having to do with comfort. Regardless of the benefits of tapering it so closely, theyre still cars that are driven on the road. Regardless of how many M cars have the same issue, that doesn't necessarily mean that BMW didn't get lazy along the way.

I get the idea of trading off comfort for performance - thats just not whats happening here.

Last edited by SgtGigglebox; 06-09-2019 at 10:27 PM.. Reason: better
Appreciate 2
Jim S215.50
GrussGott7494.50

      06-10-2019, 12:14 AM   #43
alex2364
Lieutenant Colonel
alex2364's Avatar
United_States
998
Rep
1,555
Posts

Drives: 2017 M4 ZCP
Join Date: May 2005
Location: Northern VA

iTrader: (2)

Garage List
2017 BMW M4  [0.00]
I had the same issue on my 2017 M4. I complained to my service department and they found out BMW redesigned the brake shield since my car was produced. They installed the new ones and I haven’t had any problems since. I can’t believe BMW hasn’t learned their lesson from the F80/82.
Appreciate 1
Jim S215.50

      06-10-2019, 12:47 PM   #44
DPelletier
Second Lieutenant
Canada
209
Rep
202
Posts

Drives: 2020 Z4 M40i
Join Date: May 2019
Location: Kelowna, B.C. Canada

iTrader: (0)

Quote:
Originally Posted by SgtGigglebox View Post
I think the mistake here is framing a design flaw that routinely captures stones in a position where they are forcibly ground against the internals of the braking system as something having to do with comfort. Regardless of the benefits of tapering it so closely, theyre still cars that are driven on the road. Regardless of how many M cars have the same issue, that doesn't necessarily mean that BMW didn't get lazy along the way.

I get the idea of trading off comfort for performance - thats just not whats happening here.
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,
Dave
Appreciate 1
Jim S215.50

Post Reply

Bookmarks

Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off



All times are GMT -5. The time now is 12:37 AM.




bmw
Powered by vBulletin® Version 3.8.11
Copyright ©2000 - 2019, vBulletin Solutions Inc.
1Addicts.com, BIMMERPOST.com, E90Post.com, F30Post.com, M3Post.com, ZPost.com, 5Post.com, 6Post.com, 7Post.com, XBimmers.com logo and trademark are properties of BIMMERPOST