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2019+ BMW 3 AND 4-SERIES FORUMS (G2x Generation) General G20 Sedan / G22 Coupe / G26 Gran Coupe Discussions Grinding/wind noise

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      01-13-2020, 06:13 AM   #155
Glaede
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Quote:
Originally Posted by clausmoll View Post
Interesting if this is also an issue with 19" wheels. Anyone here with 19" and M-sport breaks that can confirm this?

I could buy into the theory, that the bigger M-breakes, combined with 17" or 18" wheels could create a resonance, maybe due to some compressed air, in the wheel arches which gets better on smooth and fresh asphalt.

<Glaede> - do you know if our BMW dealer has tried with 19" wheels?
No, I don't think they have tried other wheels even though I mentioned it to the dealer. I try not to waste too much time thinking about that crappy car at the moment.. I'm enjoying the 630i GT and crossing my fingers the Touring will be fixed at some point
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      01-13-2020, 06:21 AM   #156
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The brakes and shields are indeed very different!
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      01-13-2020, 03:00 PM   #157
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I saw something strange when I removed the wheel today. It seems that the cooling channels in the disc is very effective. You can see small dots in the dirt in the inside of the wheel. I guess that this is the air from the disc that do this pattern. Could that also also be the source of the noise? Like a round harmonica😁
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      01-13-2020, 04:16 PM   #158
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Quote:
Originally Posted by Wmb5m View Post
I saw something strange when I removed the wheel today. It seems that the cooling channels in the disc is very effective. You can see small dots in the dirt in the inside of the wheel. I guess that this is the air from the disc that do this pattern. Could that also also be the source of the noise? Like a round harmonica😁
As I was running down the page saw the dirt pattern inside the wheel. Grabbed my attention, even before reading your comments.

Asking the same question...

Have you cleaned it off? Any difference?
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      01-13-2020, 04:55 PM   #159
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Quote:
Originally Posted by Wmb5m View Post

I saw something strange when I removed the wheel today. It seems that the cooling channels in the disc is very effective. You can see small dots in the dirt in the inside of the wheel. I guess that this is the air from the disc that do this pattern. Could that also also be the source of the noise? Like a round harmonica😁
That could also explain why supposedly there is no noise with 19" wheels. More space for the air to escape silently
I hope someone will be able to verify this theory.
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      01-13-2020, 05:20 PM   #160
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I picked up a G21 with 18” M (non rft) a week ago and heard a annoying grinding noise. My dealer located it to a bad bearing and replaced it. Maybe the noise got a little better, but it still there. The dealer tried some other wheels and they said it disappeared They also tried a set of the same wheels as I have but from another car in my car and they had the same noise. I run on Bridgestone Turanza and the dealer is now waiting for a respond from BMW how to proceed. I’m not sure that it’s only the tyres because I hear it also with my wintertyres but much quieter. I’m finding it very strange that they replaced a bad bearing and then said it also is the tyres! On a brand new car!
With the latest comments, and pictures... Looking for clues from earlier posts. Quoted post could be very relevant, as two different wheel sets were tried, one good, the same size the same noise.

Do you know what wheel size was tried that were quiet? 19" by any chance?
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      01-13-2020, 05:23 PM   #161
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Quote:
Originally Posted by Yossi123 View Post
That could also explain why supposedly there is no noise with 19" wheels. More space for the air to escape silently
I hope someone will be able to verify this theory.
That's where I also am in my thinking... We need a 19" wheel set on a troubled car, to confirm, or eliminate this possibility.

It is a simple thing to try by any decent dealer.
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      01-13-2020, 11:40 PM   #162
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Quote:
Originally Posted by HighlandPete View Post
Quote:
Originally Posted by XXXX View Post
I picked up a G21 with 18” M (non rft) a week ago and heard a annoying grinding noise. My dealer located it to a bad bearing and replaced it. Maybe the noise got a little better, but it still there. [COLOR="Blue"]The dealer tried some other wheels and they said it disappeared[/COLOR] [COLOR="Red"]They also tried a set of the same wheels as I have but from another car in my car and they had the same noise.[/COLOR] I run on Bridgestone Turanza and the dealer is now waiting for a respond from BMW how to proceed. I’m not sure that it’s only the tyres because I hear it also with my wintertyres but much quieter. I’m finding it very strange that they replaced a bad bearing and then said it also is the tyres! On a brand new car!
With the latest comments, and pictures... Looking for clues from earlier posts. Quoted post could be very relevant, as two different wheel sets were tried, one good, the same size the same noise.

Do you know what wheel size was tried that were quiet? 19" by any chance?
I really didn't believed the dealer that it was the tires so I wanted them to prove it again a couple a weeks later. Then they change the wheels again and no differens in sound, so they gave up. That time they used 18" but they didn't remember if they used 19" the first time. I don't think they care anymore because they used the budget for troubleshooting on my car and leave it to BMW to solve it.
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      01-14-2020, 12:54 AM   #163
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My dealer doesn't really seem to listen to my suggestions anymore, so could someone else get the dealer to try the 19" wheel?

It would be crazy if its a combination of M-Sport brakes and 18" wheels! Just don't understand why it's not present on the Sedan then..
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      01-14-2020, 02:00 AM   #164
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Quote:
Originally Posted by Glaede View Post
My dealer doesn't really seem to listen to my suggestions anymore, so could someone else get the dealer to try the 19" wheel?

It would be crazy if its a combination of M-Sport brakes and 18" wheels! Just don't understand why it's not present on the Sedan then..
I asked the dealer yesterday, if they have tried 19". He would ask the mechanic and get back to me. I'll contact him again today.

Are we infact sure that there are sedans with 18" wheels and M-sport setup including breaks that DON'T suffer from this problem?
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      01-14-2020, 03:32 AM   #165
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There is another approach, if the dealers don't want to spend more time on the problem examples. See if dealers have demo touring models with 19" wheel sets and sport brakes.

If they are silent, builds the case to try a 19" wheel set, as part of the problem solving.

The picture of the inner wheel, with what looks like evidence of a pulsing air flow, should also arouse BMW's interest.
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      01-14-2020, 03:37 AM   #166
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Quote:
Originally Posted by HighlandPete View Post
There is another approach, if the dealers don't want to spend more time on the problem examples. See if dealers have demo touring models with 19" wheel sets and sport brakes.

If they are silent, builds the case to try a 19" wheel set, as part of the problem solving.

The picture of the inner wheel, with what looks like evidence of a pulsing air flow, should also arouse BMW's interest.
Absolutely. In fact I just wrote my dealer 30 minutes ago about the 19" theory. I tried a 330i sedan M-sport with 19" wheels and M-breaks at the dealership this summer (before I ordered my Touring) - and I'm 90% sure it was silent. I'm pretty sure I would have picked up the sound if it was there.
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      01-14-2020, 03:46 AM   #167
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My thinking... I look at the picture and try and understand the reason for what appears like jets of air to the rim. Count the venting vanes in the disc, I wager they match the air pulse marks in the dirt on the rim.

As I see it.. the air flow through the disc is acting like a turbine, possibly restricting, even 'compressing' the air as it passes through the caliper housing. As the vanes reach the end of the caliper, the air pulses out into open space. The rim size could be restricting the flow and generating the sound track. May be a bit more to it, like the shape or rigidity of the backing plate, also involved in way the air is restricted and/or dispersed.
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      01-14-2020, 03:56 AM   #168
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Quote:
Originally Posted by HighlandPete View Post
My thinking... I look at the picture and try and understand the reason for what appears like jets of air to the rim. Count the venting vanes in the disc, I wager they match the air pulse marks in the dirt on the rim.

As I see it.. the air flow through the disc is acting like a turbine, possibly restricting, even 'compressing' the air as it passes through the caliper housing. As the vanes reach the end of the caliper, the air pulses out into open space. The rim size could be restricting the flow and generating the sound track. May be a bit more to it, like the shape or rigidity of the backing plate, also involved in way the air is restricted and/or dispersed.
I totally agree. It makes sense. Hopefulle my dealer will try a set of 19" wheels as I have asked him to.
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      01-14-2020, 04:21 AM   #169
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Another thought.

Looking at RealOEM, it appears the latest sport caliper (G20) is a different shape than the F30, looks like a longer 'wrapped' form. Could be relevant in the air build up in the restricted space.

Incidentally I run 17" winter rims on my car, it also has 348x36 discs. So space is just as restricted. My wheels get filthy inside, never ever seen any marks, which indicate a strange air flow from the brakes. What is different, my calipers are the standard floating type, quite open in design, although only about 6mm clearance to the inner rim.

BTW, I've got a Brembo 348x36 disc here in my office, it has 48 venting fins, 24+24. One solid, one slotted, alternating around the disc. Assuming the G21 discs are the same, we have 24 'inlets', I expect there are 24 marks in the dirt.
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      01-14-2020, 04:39 AM   #170
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Quote:
Originally Posted by HighlandPete View Post
Another thought.

Looking at RealOEM, it appears the latest sport caliper (G20) is a different shape than the F30, looks like a longer 'wrapped' form. Could be relevant in the air build up in the restricted space.

Incidentally I run 17" winter rims on my car, it also has 348x36 discs. So space is just as restricted. My wheels get filthy inside, never ever seen any marks, which indicate a strange air flow from the brakes. What is different, my calipers are the standard floating type, quite open in design, although only about 6mm clearance to the inner rim.

BTW, I've got a Brembo 348x36 disc here in my office, it has 48 venting fins, 24+24. One solid, one slotted, alternating around the disc. Assuming the G21 discs are the same, we have 24 'inlets', I expect there are 24 marks in the dirt.
24 inlets and 24 expected marks in the dirt - that's pretty strong proof of something odd is going on
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      01-14-2020, 04:46 AM   #171
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Here's a way to temporarily eliminate the airflow. Not recommending anyone take it on, but I know I would.

Wrap the vented area with insulation tape, a couple of times around the disc, make sure its contained in the area between the disc faces. Try a careful drive, get to the speeds where there is normally a problem. Just don't brake hard and heat the discs too much.
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      01-14-2020, 05:10 AM   #172
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Originally Posted by HighlandPete View Post
Here's a way to temporarily eliminate the airflow. Not recommending anyone take it on, but I know I would.

Wrap the vented area with insulation tape, a couple of times around the disc, make sure its contained in the area between the disc faces. Try a careful drive, get to the speeds where there is normally a problem. Just don't brake hard and heat the discs too much.


Tempting...
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      01-14-2020, 05:49 AM   #173
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Originally Posted by clausmoll View Post


Tempting...
DO IT Claus ;-)

I would, if I had the car
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      01-14-2020, 06:43 AM   #174
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DO IT Claus ;-)

I would, if I had the car
Okay - I did it. It took 20 minutes out of my lunch break.

There was no difference in the noise what so ever. But I do still suspect the calipers/brake plate/wheel size theory.

Last edited by clausmoll; 01-14-2020 at 06:49 AM..
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      01-14-2020, 06:53 AM   #175
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Okay - I did it. It took 20 minutes out of my lunch break.

There was no difference in the noise what so ever. But I do still suspect the calipers/brake plate/wheel size theory.
Wow! You are the man. Well done!

At least the test eliminates it being directly related to 'generated' airflow from the disc/caliper combination.

I agree there could still be an issue due to something about the complete assembly. Trying 19" wheels has to be specifically tested, it is a process of elimination.
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      01-14-2020, 06:56 AM   #176
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Wow! You are the man. Well done!

At least the test eliminates it being directly related to 'generated' airflow from the disc/caliper combination.

I agree there could still be an issue due to something about the complete assembly. Trying 19" wheels has to be specifically tested, it is a process of elimination.


I agree!
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