[Jim S]

Have any new g20 owners experienced a problem with stones getting trapped in the front M Sport brakes?

I have a new g29 Z4 which has the exact same M Sport brakes design as the g20 and stones are regularly getting trapped in my front brakes. This has happened to me five times in the first 12 weeks of ownership. Some other g29 owners have experienced the same problem. The stone gets trapped between the shield and brake disc and it sounds absolutely horrendous.

I would be interested to hear whether or not any g20 owners with M Sport brakes have experienced the same problem.

[Jbrock22]

I have an F30 with Sport Brakes, it happened once.

[Jim S]

Originally Posted by Jbrock22

I have an F30 with Sport Brakes, it happened once.

Thanks for your feedback jbrock22. I am trying to get BMW to fix the very poor design of the front shields as they are a magnet for trapping stones. The more owners that the report the problem the better.

[Jim S]

The photograph below highlights the problem.

This is the front M Sport brake assembly on the G29 Z4, which is identical to the new G20 3 series with M Sport brakes. The wide open top is like an open mouth and a magnet to attract stones and the bottom of the shield bends inwards towards the brake disc closing the gap and traps the stone. You will also see that the bottom of the shield is positioned hard up against the track rod end and therefore can’t be bent outwards to increase the size of the gap to let the stone escape.

[Ilyam5]

All M brakes have that issue. If you drive on stones with sticky tires it will happen. I used to cut those back plates off. You really don't need them.

[Jim S]

Originally Posted by Ilyam5

All M brakes have that issue. If you drive on stones with sticky tires it will happen. I used to cut those back plates off. You really don't need them.

Thanks for your input Ilyam5. I may end up doing that but at the moment the car is under warranty for 3 years.

[upsidedownfunnel]

It looks like BMW designed these new shields to be able to come out without removing the wheel bearing. You just need to remove the rotor and caliper. Maybe you can just ask the dealer to do that if you can't do that yourself. I doubt it would void any warranty. Obviously during testing, they probably don't expect most people who need to drive on gravel/stony roads to get the M Performance version of the car. In your particular situation, they might be fine with you removing them.

[Jim S]

Originally Posted by upsidedownfunnel

It looks like BMW designed these new shields to be able to come out without removing the wheel bearing. You just need to remove the rotor and caliper. Maybe you can just ask the dealer to do that if you can't do that yourself. I doubt it would void any warranty. Obviously during testing, they probably don't expect most people who need to drive on gravel/stony roads to get the M Performance version of the car. In your particular situation, they might be fine with you removing them.

The problem is happening on main roads with some pot holes and a few stones, not gravel tracks or back roads. I have an ongoing issue with BMW to try to get the problem resolved on my car. Removing the shields may be the outcome, without voiding the warranty.

Thanks for your input.

[Jbrock22]

Originally Posted by Jim S

The problem is happening on main roads with some pot holes and a few stones, not gravel tracks or back roads. I have an ongoing issue with BMW to try to get the problem resolved on my car. Removing the shields may be the outcome, without voiding the warranty.

Thanks for your input.

Can you bend the bottom of the shields away slightly from the rotor to allow the stone(s) to fall out?

[Jim S]

Originally Posted by Jbrock22

Can you bend the bottom of the shields away slightly from the rotor to allow the stone(s) to fall out?

No, because the bottom of the shield is very close to the track rod end.

[tosswill]

Sorry to fire up an old thread, but does anyone know if this issue only happens with a 20" rim & sticky tires vs. 19"?

I run Michelin PS4S mounted on 20" rims on my 2020 G20 M340i and almost every time I drive up a gravel/dirt road I have this issue... It has only happened to my front brakes, so I'm wondering if I change my setup to a staggered 19" front with 20" rear with the Michelin PS4S whether that will solve the issue?

Anyone have any experience/advice on how to resolve? I've seen someone mention removing the brake shield, which I'm open to as long as there aren't any knock-on effects... I'm also open to upgrading the brakes to the slotted discs if that's likely to help as well, although I can't imagine it would...

Cheers!

[_E90S65_]

OP,

I have yet to experience this on my G20.

But I've experienced something similar on every other BMW owned.

I learned this trick on the E90 forum, and it worked every time!

Come to a complete stop.
Put car in Reverse. Punch it — hard. Then brake — hard.
Make sure car travels back at least 50-100ft.
This violent blast in Reverse will eject the rock.

Some on the F80 forum found gently bending the shield away from the rotor to help.

[Blubaron79]

Happened to me over the winter.

I was told to drive forward, slam on the brakes (obviously stop), and then throw it in reverse.

[Jbrock22]

It happened on my M340. I removed the wheel and to clear the stone it took a mallet and a stick to get it out.

[Baldwin]

I've had a '22 G20 for about 3 months and it's happened once.

[fueledbymetal]

Originally Posted by _E90S65_

OP,

I have yet to experience this on my G20.

But I've experienced something similar on every other BMW owned.

Same here.

[TheJudge001]

Originally Posted by Jim S

Have any new g20 owners experienced a problem with stones getting trapped in the front M Sport brakes?

I have a new g29 Z4 which has the exact same M Sport brakes design as the g20 and stones are regularly getting trapped in my front brakes. This has happened to me five times in the first 12 weeks of ownership. Some other g29 owners have experienced the same problem. The stone gets trapped between the shield and brake disc and it sounds absolutely horrendous.

I would be interested to hear whether or not any g20 owners with M Sport brakes have experienced the same problem.

So I have just purchased a 2021 bmw m340i and it has the m performance brakes. Just yesterday evening I heard the loudest squeeling ever it worse when I slowed down and when turned right. I was sure it was a stone or dirt. After shitting myself about what it could be I found this post. I immediately called bmw roadside assistance and this is where it got interesting.

As soon as I told the lady there’s a screeching sound, she asked me immediately is it from one of the front wheels. When I replied yes she said it’s a stone. She said it’s the most awful sound but the most common thing on them. BMW technicians have told them to pass on the following technique to dislodge the stones.

Drive ahead and do a full emergency stop and do the same in reverse. Repeat up to 7 times. 9/10 times this works apparently but if it’s really stuck a technician will need to take the wheel off to access the area.

Luckily I have cover but hope the technique works for someone. I will try and find a place do it in the morning if possible see what happens.

Really shit design I must say 😂 but love the car nonetheless

[TheJudge001]

Originally Posted by TheJudge001

So I have just purchased a 2021 bmw m340i and it has the m performance brakes. Just yesterday evening I heard the loudest squeeling ever it worse when I slowed down and when turned right. I was sure it was a stone or dirt. After shitting myself about what it could be I found this post. I immediately called bmw roadside assistance and this is where it got interesting.

As soon as I told the lady there’s a screeching sound, she asked me immediately is it from one of the front wheels. When I replied yes she said it’s a stone. She said it’s the most awful sound but the most common thing on them. BMW technicians have told them to pass on the following technique to dislodge the stones.

Drive ahead and do a full emergency stop and do the same in reverse. Repeat up to 7 times. 9/10 times this works apparently but if it’s really stuck a technician will need to take the wheel off to access the area.

Luckily I have cover but hope the technique works for someone. I will try and find a place do it in the morning if possible see what happens.

Really shit design I must say 😂 but love the car nonetheless

UPDATE. bmw road side assistance came out today and removed a large stuck between the brake disc and the brake dust shield. No more screeching!