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BMW 5-Series (G30) Forum Wheels | Tires | Suspension | Brakes | Chassis G30 - front brake disc broke due to a stone

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      12-17-2018, 07:50 AM   #1
robert86
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G30 - front brake disc broke due to a stone

Hello friends,

I have a G30 2018, M-Pack, M-Sport brakes.

I just drove through a lot of snow & mud (salt from road), bad weather about 2000Km. First thing is that x-Drive worth all money, the car is absolutely fantastic 4WD experience.

Now last night I noticed a rumble noise from front right wheel. Also while washing yesterday, the same wheel was some kind brown (initially I said from mud).

I went to representative and they said that was a stone between pads and disk ?! Ok, but disk is broken... a lots of irregular lines. They also said that i normal and brakes can hold another 2000Km.

The car have 38.000 km and I decided to replace both front discs and pads.
This will cost me 1000 eur.

No warning at all on electronics.
For old cads I had there was a sensor or at least a mechanical noise.

I didn't drove like a maniac but definitely nor like a old man, despite the stone, it seems that at 40..50k the front pads shall be replaced anyhow.

Is this normal that a stone can ruin your disc?

Appreciate your comments,
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      03-01-2019, 11:31 AM   #2
JH1
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It is possible for small stones to get stuck within the calliper, quite often they will eventually come out of their own accord but they can cause damage in the process. If the stone is out and nothing has cracked you should be fine despite the ring marks you see on the disc, they will eventually wear even again over time and shouldn't really affect your braking efficiency to any great extent.

On a similar note, I have just had to have my rear discs and pads replaced under warranty after only 20,000 miles. They are barely worn but have warped for no apparent reason other than the quality not being what they used to be. Again, my car is driven very respectfully so it doesn't get a hard life, so I was somewhat surprised this should happen.

On the positive side, my BMW dealer has been very efficient and made the process as painless as possible, so I'm thankful for that.
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      03-01-2019, 08:57 PM   #3
saporitj
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Quote:
Originally Posted by JH1 View Post
It is possible for small stones to get stuck within the calliper, quite often they will eventually come out of their own accord but they can cause damage in the process. If the stone is out and nothing has cracked you should be fine despite the ring marks you see on the disc, they will eventually wear even again over time and shouldn't really affect your braking efficiency to any great extent.

On a similar note, I have just had to have my rear discs and pads replaced under warranty after only 20,000 miles. They are barely worn but have warped for no apparent reason other than the quality not being what they used to be. Again, my car is driven very respectfully so it doesn't get a hard life, so I was somewhat surprised this should happen.

On the positive side, my BMW dealer has been very efficient and made the process as painless as possible, so I'm thankful for that.
I had my rotors warp once on my Volvo. I was told it can be caused by lug nuts torqued incorrectly and hot brakes going through a puddle of water. Not sure if it was the same in your case or it was even correct info that I was given. The more performance brakes are softer. Wish I could put on slotted disc when it's time to change mine. But for now I'm ok with only 1,200 miles on car.
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      03-02-2019, 02:51 AM   #4
JH1
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I'm haven't travelled through water in mine and usual driving in wet weather won't affect them; discs would need a good submerge in cold water whilst properly hot to warp. Undoubtedly though, it's extremes of heat/cold that will cause the issue. Not sure about the torque being a cause; haven't heard that one before.
BMW now have a brake drying facility which minimally applies the brakes in wet weather to keep moisture off the disc ensuring immediate brake efficiency when you need to hit the brake pedal. I think this could likely be a cause of excessive heat and hence could lead to the discs warping if it isn't operating exactly as intended.
I'm also aware from a number of different sources, that the quality of consumable parts has declined considerably in the last 5-10 years and they just won't last or perform like they have in the past and are now prone to more faults/issues like this.
Something else to factor into the cost of ownership I guess!!
At least on this occasion, BMW accepted it was a fault/defect due to the parts and replaced them under warranty which was a decent thing to do.

Last edited by JH1; 03-02-2019 at 02:57 AM.. Reason: Additional text
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