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      08-28-2008, 02:44 AM   #1
kennethcho1337
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brake rotors

do the OEM brake rotors hold up well on the track? no cracking issues? and also are the rotors a 2 piece setup or are they single piece?
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      08-28-2008, 12:03 PM   #2
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Quote:
Originally Posted by kennethcho1337 View Post
do the OEM brake rotors hold up well on the track? no cracking issues? and also are the rotors a 2 piece setup or are they single piece?
no cracking issue, however they warp quite easily - I have done 3 track days and the car is in the shop now to get new rotors and pads...

not sure what you mean by 2 piece setup?? There are 2 ventilated discs per side check here:
http://bmwfans.info/original/E92/Cou...4/ill-34_1423/
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      08-28-2008, 01:03 PM   #3
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Quote:
Originally Posted by kennethcho1337 View Post
do the OEM brake rotors hold up well on the track? no cracking issues? and also are the rotors a 2 piece setup or are they single piece?
They are a two piece design. An aluminum hat with the disk connected by pins that allow for thermal expansion while reducing heat transfer to the hub.
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      08-28-2008, 09:58 PM   #4
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R8 brake rotor = same design as M3 brake rotor!

About the warping, are single piece rotors easier to warp?
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      08-28-2008, 10:13 PM   #5
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2 piece rotors are supposedly more resistant to warping, not less. Although they don't transfer as much heat to the hub the design is allow the disc material to expand independently from the carrier. What most diagnose as a warped disc is usually uneven pad material transfer due to pads exceeding their temperature range or incorrect bedding-in procedure. I've done this myself a few times.
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      08-28-2008, 10:41 PM   #6
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Quote:
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no cracking issue, however they warp quite easily - I have done 3 track days and the car is in the shop now to get new rotors and pads...
Are you absolutely sure you have warped rotors? They should not warp that easily. My brakes develop a slight vibration toward the end of the track day, but it goes away after a couple of weeks of driving, which makes me think the issue has to with the pads or something else. This has happened to me twice now.
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      08-28-2008, 10:52 PM   #7
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Quote:
Originally Posted by sfbimmer13 View Post
no cracking issue, however they warp quite easily - I have done 3 track days and the car is in the shop now to get new rotors and pads...

not sure what you mean by 2 piece setup?? There are 2 ventilated discs per side check here:
http://bmwfans.info/original/E92/Cou...4/ill-34_1423/
Is the rotor and pad replacement covered under warranty with track use?
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      08-28-2008, 11:03 PM   #8
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Quote:
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Is the rotor and pad replacement covered under warranty with track use?
Depends on your dealer, judgement call. Some people have had goodluck, others no.

edit: Not a brake expert, but unless your pulling up your hand brake after some hotlaps or really really pushing them hard find it hard to believe that they warped.
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      08-29-2008, 12:56 AM   #9
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Depends on your dealer, judgement call. Some people have had goodluck, others no.
I'm sure they gotta be a bit suspicious if you come in for this service every 4000 miles. I wonder what the limit is...
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      08-29-2008, 07:58 AM   #10
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I'm sure they gotta be a bit suspicious if you come in for this service every 4000 miles. I wonder what the limit is...
They won't keep on replacing your rotors at 5000 miles intervals. They would most likely do it once at that rate. Over the 4 years, it is not uncommon to get 3 or so replacements.
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      08-29-2008, 10:52 AM   #11
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Please tell me that you don't use your E-brake when you park your car after lapping sessions. I assume that you don't, but I have seen it too many times.
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      08-29-2008, 11:08 AM   #12
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Quote:
Originally Posted by lucid View Post
Are you absolutely sure you have warped rotors? They should not warp that easily. My brakes develop a slight vibration toward the end of the track day, but it goes away after a couple of weeks of driving, which makes me think the issue has to with the pads or something else. This has happened to me twice now.
no not absolutely sure, however when they replaced them they said that the rotors where shot...how would I actually find out for sure if they are warped - I kept the old rotors?

Quote:
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Is the rotor and pad replacement covered under warranty with track use?
as others have said already it really depends on your service manager...this time I offered to pay for the replacement since I know that I have cooked the brakes...next time it is on BMW tap

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Please tell me that you don't use your E-brake when you park your car after lapping sessions. I assume that you don't, but I have seen it too many times.
nope
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      08-29-2008, 12:35 PM   #13
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no not absolutely sure, however when they replaced them they said that the rotors where shot...how would I actually find out for sure if they are warped - I kept the old rotors?
They would need to be mounted and rotated while being measured with a sensitive probe for deflection/uneven surface. I don't know what the spec is for these rotors, but we are probably talking about in the region of 0.001".

The rotors can be glazed due to overheating of local areas, which changes the characteristic of the metal and causes uneven friction across the surface of the rotor, which results in vibration. The first time that happened to me, it went away after a few weeks of driving as I mentioned, but it might very well not, in which case you need to replace the rotor.
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      08-29-2008, 12:46 PM   #14
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Quote:
Originally Posted by lucid View Post
They would need to be mounted and rotated while being measured with a sensitive probe for deflection/uneven surface. I don't know what the spec is for these rotors, but we are probably talking about in the region of 0.001".

The rotors can be glazed due to overheating of local areas, which changes the characteristic of the metal and causes uneven friction across the surface of the rotor, which results in vibration. The first time that happened to me, it went away after a few weeks of driving as I mentioned, but it might very well not, in which case you need to replace the rotor.
thanks for the comprehensive answer - since I already replaced the rotors I am not going to obsess over it
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      08-29-2008, 05:41 PM   #15
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If the OEM rotors are two piece, does BMW just replace the disc or both the disc and hat when replacing the rotors under warranty.
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      08-30-2008, 02:29 AM   #16
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they are two piece floating roters with an aluminum hub hat and an iron disk, they replace the entire disc unit at one time.

however a lot of vibrations from the track are not always due to warping but due to brake pad material melting to the rotor. if so it will wear off and go away after a few thou miles, the only way to tell is to but the brake rotors on a lathe.

two pc. rotors should resist warping better than a one peice rotor (a single pieceof iron, hub and disc. )
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      08-30-2008, 10:23 PM   #17
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These issues sound pad related...wrongpads for the track. Ive had the material buildup on the rotor issue on other cars and they always went back to normal after a week of normal driving, although I left the race-pads on until they cleared the rotors.
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      08-31-2008, 02:51 PM   #18
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Quote:
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These issues sound pad related...wrongpads for the track. Ive had the material buildup on the rotor issue on other cars and they always went back to normal after a week of normal driving, although I left the race-pads on until they cleared the rotors.
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