Dealer says warped rotors?

[crumbelieve]

Hi Guys,

Seems like there is a lot of technical knowledge here (I have absolutely none) so thought I'd get your opinions.

My car is stock ~25,000 miles and have recently been feeling shaking and rumbling under braking at highway speeds (~60mph). Car has never been tracked and I "bedded" the brake pads upon delivery as suggested by many owners in the forum. Also tried some harder braking to remove any potential buildup as suggested on other threads, but the issue persists.

Dealer seems to think it is a warped rotor, and is quoting ~1100 USD to replace the front pair. Seems unlikely that the rotors are warped under my usage, but not sure. Planning to swap winter wheels with summer wheels this weekend and retesting as it seems improperly torqued wheels could also cause the problem.

Any other ideas / suggestions before letting dealer rack up the bills?

Thanks!
AC

[craina]

From what I understand it is highly unlikely that you warped the rotor. Pad deposits or wheels that have become out of balance could be the issue. Assuming the wheels do not fix the issue then I would suggest replacing the rotors yourself or at least taking it to an independent shop to do the work. A new set of rotors is ~$600 and swapping rotors can be accomplished with basic hand tools and an hour or two of your time.

[MightyMouseTech]

Most common reason for warped rotors, if that is what it is, is improperly torqued wheel bolts, has nothing to do with driving.

Do you ALWAYS torque the bolts to proper spec?

If that was the cause, removing the wheels and retorqing will not fix it.

[crumbelieve]

Originally Posted by craina

From what I understand it is highly unlikely that you warped the rotor. Pad deposits or wheels that have become out of balance could be the issue. Assuming the wheels do not fix the issue then I would suggest replacing the rotors yourself or at least taking it to an independent shop to do the work. A new set of rotors is ~$600 and swapping rotors can be accomplished with basic hand tools and an hour or two of your time.

Craina,

Thanks for the good advice. I thought wheels might have been out of balance as well, but then they should shake while coasting at 60mph as well, right? I'm only having an issue under braking, which led me to believe something was up with the brakes..

[crumbelieve]

Originally Posted by MightyMouseTech

Most common reason for warped rotors, if that is what it is, is improperly torqued wheel bolts, has nothing to do with driving.

Do you ALWAYS torque the bolts to proper spec?

If that was the cause, removing the wheels and retorqing will not fix it.

MightyMouse,

I'm ashamed to admit that I didn't do my wheels myself, let the dealer do it when I went in for service. Very possible they over-torqued using an air-wrench...

If that's indeed the case, this will be an expensive lesson..

[MightyMouseTech]

If it was at the dealer, I highly doubt they over torqed them.

[The Wind Breezes]

Dealer's a dumbass, problem was pads aren't bedded in properly.

Solution is new pads / rotors.

[CarJunkie]

Originally Posted by MightyMouseTech

If it was at the dealer, I highly doubt they over torqed them.

That has not been my experience. I properly torque the wheels on all of my cars when I do my seasonal swaps. Whenever there has been a reason for wheels to be removed during a dealer service, I loosen and re-torque them immediately or the next swap will be a b!#ch.

[bdaddylo]

Originally Posted by MightyMouseTech

Most common reason for warped rotors, if that is what it is, is improperly torqued wheel bolts, has nothing to do with driving.

Do you ALWAYS torque the bolts to proper spec?

If that was the cause, removing the wheels and retorqing will not fix it.

I think this is less likely on a floating rotor application like the M3's.

[MightyMouseTech]

Originally Posted by CarJunkie

That has not been my experience. I properly torque the wheels on all of my cars when I do my seasonal swaps. Whenever there has been a reason for service, I loosen and re-torque them immediately or the next swap will be a b!#ch.

Wow, dealer over torqueing them. If they can't do that right, I would not let them check my washer fluid.

[HP Autosport]

Originally Posted by crumbelieve

Hi Guys,

Seems like there is a lot of technical knowledge here (I have absolutely none) so thought I'd get your opinions.

My car is stock ~25,000 miles and have recently been feeling shaking and rumbling under braking at highway speeds (~60mph). Car has never been tracked and I "bedded" the brake pads upon delivery as suggested by many owners in the forum. Also tried some harder braking to remove any potential buildup as suggested on other threads, but the issue persists.

Dealer seems to think it is a warped rotor, and is quoting ~1100 USD to replace the front pair. Seems unlikely that the rotors are warped under my usage, but not sure. Planning to swap winter wheels with summer wheels this weekend and retesting as it seems improperly torqued wheels could also cause the problem.

Any other ideas / suggestions before letting dealer rack up the bills?

Thanks!
AC

My question for them would be, "what's the runout?"

There is always options of aftermarket high quality German made rotors or the two-piece floating rotors(these are overkill if you don't track) from PFC and Stoptech.

[CarJunkie]

Originally Posted by MightyMouseTech

Wow, dealer over torqueing them. If they can't do that right, I would not let them check my washer fluid.

Now that I am out of warranty, they won't be doing anything.

And this is not just BMW, our local Toyota and Mercedes dealerships are the same, as was the Toyota dealership in Maine before we moved west. I swear they use air tools without any torque sticks. Just plain laziness. I always check and re-do the wheels.

[crumbelieve]

Hi guys,

I went to the dealer this weekend, they measured the rotors and said that they were all to up specification, which was a relief. They think it is just rust buildup from infrequent usage and will go away after usage. I did a couple of hard brakes, but the issue persists - have you guys experienced this?

Thanks!
AC

[bodega_bladerunner]

The "Warped" Brake Disc and Other Myths of the Braking System

http://www.stoptech.com/technical-su...nd-other-myths

[GimmeanM]

Originally Posted by greenc51

The "Warped" Brake Disc and Other Myths of the Braking System

http://www.stoptech.com/technical-su...nd-other-myths

...a good read.

[jlc45]

Very interesting.

[HP Autosport]

Originally Posted by crumbelieve

Hi guys,

I went to the dealer this weekend, they measured the rotors and said that they were all to up specification, which was a relief. They think it is just rust buildup from infrequent usage and will go away after usage. I did a couple of hard brakes, but the issue persists - have you guys experienced this?

Thanks!
AC

Did they measure runout? Make sure they do it both on the rotor and the hub.

[nachob]

Originally Posted by craina

From what I understand it is highly unlikely that you warped the rotor. Pad deposits or wheels that have become out of balance could be the issue. Assuming the wheels do not fix the issue then I would suggest replacing the rotors yourself or at least taking it to an independent shop to do the work. A new set of rotors is ~$600 and swapping rotors can be accomplished with basic hand tools and an hour or two of your time.

Pad deposits more common. I concur. If you read the manual. It tells you these are high performance brakes and they should periodically used with heavy braking or something like that. My car was parked for winter and had the same issue. Dealer replaced rotors under warranty. They are old enough that it probably couldn't hurt. You have nothing to lose by having them machines just enough to clean the face and not take material much material off.

Another option is to find a set of OEM replacements made by the same people as original but don't say BMW. They are out there and probably $400 total. Of course dealer won't do that.

[Tom303]

My recommendation would be to get a set of lightly used racing pads and do some hard braking/bedding. Then put the stock pads back on. It's amazing how racing pads will resurface your rotors.

[MightyMouseTech]

Originally Posted by Tom303

My recommendation would be to get a set of lightly used racing pads and do some hard braking/bedding. Then put the stock pads back on. It's amazing how racing pads will resurface your rotors.

Except you have now bedded the rotors in with a different compound. Not all brake compounds are compatible.

On my winter/track car I run Hawk HPS on the street only so I can run my Hawk DTC-60 on the track without changing rotors. All Hawk compounds are compatible with each other.