Hairline cracks on rotors

e46revspeed · 12-02-2016, 06:24 PM

Hi ,i recently bought some used M6 brake kit from a member on here. I just notice that both front rotors have alot of tiny hairline cracks on the surface and by the cross drilled holes. I posted a picture can anyone tell me if this is normal or does it needs to be replaced. thanks

reaton31 · 12-03-2016, 10:25 AM

I just checked my original stock rotors on my '14 M6 with 29K miles and no cracks.

Pazzo009 · 12-03-2016, 12:29 PM

This can happen to rotors that were possibly used for track work or not cared for properly. If you're hard on your brakes and the brake dust is not cleaned out of the holes, this happens. The dust stays in the holes, the dust is metal flakes. The flakes stay in there and rust. As it rusts, it expands and can weaken the metal. That is how it was explained to me. Maybe someone else more educated on it can explain the science better than myself. You should be okay as long as you're not tracking the car, but inspect those holes and clean accordingly if they fill up with dust.

melvyn · 12-03-2016, 02:08 PM

Them discs look fooked, there must be at least a 2 -3 mill lip on them

e46revspeed · 12-03-2016, 07:19 PM

Quote:

Originally Posted by aculeg87

This can happen to rotors that were possibly used for track work or not cared for properly. If you're hard on your brakes and the brake dust is not cleaned out of the holes, this happens. The dust stays in the holes, the dust is metal flakes. The flakes stay in there and rust. As it rusts, it expands and can weaken the metal. That is how it was explained to me. Maybe someone else more educated on it can explain the science better than myself. You should be okay as long as you're not tracking the car, but inspect those holes and clean accordingly if they fill up with dust.

thanks for the info. I dont track the car, just a daily driver so I hope it last a bit.

TrevorM3 · 12-03-2016, 09:46 PM

i suppose it's OK to drive normally with them. Just get them replaced when you can.

please don't do triple digits on these rotors.

rambino · 12-04-2016, 03:40 PM

Your Completely FINE! This is normal, my car has them too. If the cracks get super long and connect between holes then you can start worrying.. This is very common topic on the Porsche forums.

The M6 blue brakes can handle the high heat and aggression no problem, they are track tested.. your good to go.. Cheers

e46revspeed · 12-04-2016, 06:57 PM

Quote:

Originally Posted by rambino

Your Completely FINE! This is normal, my car has them too. If the cracks get super long and connect between holes then you can start worrying.. This is very common topic on the Porsche forums.

The M6 blue brakes can handle the high heat and aggression no problem, they are track tested.. your good to go.. Cheers

thanks for the feedback...make me feel a little easier about it.

M6-Coupe · 12-05-2016, 01:33 AM

Take a look at this thread I posted last year
http://f10.m5post.com/forums/showthread.php?t=1112127

e46revspeed · 12-05-2016, 01:59 AM

Thanks for the link..much appreciated

e46revspeed · 12-09-2016, 04:08 PM

It was an eyesore so went out and bought some new rotors and pads. Just being on the safe side i guess.

ChrisCM6 · 12-10-2016, 01:07 PM

Quote:

Originally Posted by e46revspeed

It was an eyesore so went out and bought some new rotors and pads. Just being on the safe side i guess.

Do you know what mileage was on them? Or how much of a lip there was?

I got this a lot on my stoptech discs, but did quite a few track days with them. Didnt help

e46revspeed · 12-11-2016, 01:23 AM

Quote:

Originally Posted by ChrisCM6

Do you know what mileage was on them? Or how much of a lip there was?

I got this a lot on my stoptech discs, but did quite a few track days with them. Didnt help

Sorry no, just saw a lot of stress crack. When to the dealer and talked to my SA to see if its normal. He told me there were too many cracks which was not normal.

M6-Coupe · 12-11-2016, 01:32 AM

Quote:

Originally Posted by e46revspeed

It was an eyesore so went out and bought some new rotors and pads. Just being on the safe side i guess.

You bought on your own? I already posted the link to show the bulletin.
I had them replaced my rotors and pads 3 times in 3 years FOR FREE! It's part of zero maintenance program!

e46revspeed · 12-11-2016, 02:37 AM

Quote:

Originally Posted by M6-Coupe

You bought on your own? I already posted the link to show the bulletin.
I had them replaced my rotors and pads 3 times in 3 years FOR FREE! It's part of zero maintenance program!

Yeah i had to buy em. My car is a 650 i...bought these used from a guy on this forum to retrofit these on a 650i. O dont think the dealer will replace them.

doughboy · 12-12-2016, 05:48 AM

Quote:

Originally Posted by M6-Coupe

You bought on your own? I already posted the link to show the bulletin.
I had them replaced my rotors and pads 3 times in 3 years FOR FREE! It's part of zero maintenance program!

I read the bulletin and it says they are not to be replaced and that cracks up to 13mm are normal. The bulletin title is even "Cracks are NORMAL".

This is the same as UK BMW guidance.

How did you get yours replaced? you must have had 13mm+ cracks?

M6-Coupe · 12-12-2016, 09:19 PM

Quote:

Originally Posted by doughboy

I read the bulletin and it says they are not to be replaced and that cracks up to 13mm are normal. The bulletin title is even "Cracks are NORMAL".

This is the same as UK BMW guidance.

How did you get yours replaced? you must have had 13mm+ cracks?

We have nice dealerships in Orange County

13M5F10 · 12-31-2016, 02:02 PM

I took mine into BMW for the same issue and was told it's normal and not covered under warranty. I did do a lot of hard braking from racing and high speed runs

12-02-2016, 06:24 PM	#1
e46revspeed Captain 104 Rep 620 Posts Drives: F06 & E89 Join Date: Jul 2008 Location: oc iTrader: (6)	Hairline cracks on rotors Hi ,i recently bought some used M6 brake kit from a member on here. I just notice that both front rotors have alot of tiny hairline cracks on the surface and by the cross drilled holes. I posted a picture can anyone tell me if this is normal or does it needs to be replaced. thanks Attached Images __________________ Squattin on Megan Racing and Vertini Monaco
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12-03-2016, 10:25 AM	#2
reaton31 New Member 3 Rep 14 Posts Drives: 2017 Alpina B6 Join Date: Jul 2016 Location: 92694 iTrader: (0) Garage List 2016 Alpina B6 [0.00] 2014 BMW M6 Comp [0.00]	I just checked my original stock rotors on my '14 M6 with 29K miles and no cracks.
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12-03-2016, 12:29 PM	#3
Pazzo009 Major 1109 Rep 1,314 Posts Drives: X5M,M3(46&36),812SF Join Date: Sep 2009 Location: NY&GA iTrader: (0)	This can happen to rotors that were possibly used for track work or not cared for properly. If you're hard on your brakes and the brake dust is not cleaned out of the holes, this happens. The dust stays in the holes, the dust is metal flakes. The flakes stay in there and rust. As it rusts, it expands and can weaken the metal. That is how it was explained to me. Maybe someone else more educated on it can explain the science better than myself. You should be okay as long as you're not tracking the car, but inspect those holes and clean accordingly if they fill up with dust.
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12-03-2016, 02:08 PM	#4
melvyn Lieutenant 267 Rep 436 Posts Drives: 2018 M3 CS Join Date: Jun 2011 Location: isle of man iTrader: (0)	Them discs look fooked, there must be at least a 2 -3 mill lip on them
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12-03-2016, 09:46 PM	#6
TrevorM3 Banned 3322 Rep 8,083 Posts Drives: 6.3 AMG Join Date: Apr 2013 Location: Florida iTrader: (0)	i suppose it's OK to drive normally with them. Just get them replaced when you can. please don't do triple digits on these rotors.
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12-04-2016, 03:40 PM	#7
rambino M Master 74 Rep 551 Posts Drives: M6 / X6M Join Date: Jun 2007 Location: SoCal / Florida iTrader: (3)	Your Completely FINE! This is normal, my car has them too. If the cracks get super long and connect between holes then you can start worrying.. This is very common topic on the Porsche forums. The M6 blue brakes can handle the high heat and aggression no problem, they are track tested.. your good to go.. Cheers __________________ M History: E46 M3, E92 M3, E63 M6, F13 M6 Comp Pkg, E71 X6M
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12-05-2016, 01:33 AM	#9
M6-Coupe Major General 1125 Rep 6,066 Posts Drives: F92 M8 Join Date: Feb 2014 Location: Bay area iTrader: (0)	Take a look at this thread I posted last year http://f10.m5post.com/forums/showthread.php?t=1112127 __________________ Current : 2020 F92 Black Sapphire M8 - ZF8 Gone : 2018 F80 Mineral Gray M3 - 6MT Gone : 2016 F82 Austin Yellow M4 - 6MT Gone : 2013 F13 Sakhir Orange M6 -7DCT Gone: 2013 F13 Alpine White 650i -ZF8
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12-05-2016, 01:59 AM	#10
e46revspeed Captain 104 Rep 620 Posts Drives: F06 & E89 Join Date: Jul 2008 Location: oc iTrader: (6)	Thanks for the link..much appreciated
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12-09-2016, 04:08 PM	#11
e46revspeed Captain 104 Rep 620 Posts Drives: F06 & E89 Join Date: Jul 2008 Location: oc iTrader: (6)	It was an eyesore so went out and bought some new rotors and pads. Just being on the safe side i guess. __________________ Squattin on Megan Racing and Vertini Monaco
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12-31-2016, 02:02 PM	#18
13M5F10 Hide! My wife's coming! 812 Rep 2,816 Posts Drives: 2013 BMW M5 \| MSR Stage 3 Join Date: Jun 2015 Location: Las Colinas, TX iTrader: (5)	I took mine into BMW for the same issue and was told it's normal and not covered under warranty. I did do a lot of hard braking from racing and high speed runs __________________ * SOLD * 2013 BMW M5 \| Space Grey \| MSR Stage 3 Tune \| Catless Downpipes \| MSR Intake and Charge Pipes \| MSR Exhaust (Prototype) \| Vorsteiner Rear Diffuser \| RW Carbon Front Lip \| RW Carbon Trunk Spoiler\| Vorsteiner VS-310 Forged Wheels \| Escort 9500CI w/Laser Jammers
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