[SwissG80]

Hello all,

About a month ago I drove on track with my G80 M3 (its first time), and have driven about 1500 km since (more or less 1000 miles).
I drove about 25-30 laps in total, in short 4 laps sessions including a cooldown lap, waiting 15-20 minutes between sessions.
I did not push it particularly hard, and was especially kind on the braking. The car had about 10'000 km (7500 miles) on the clock that day.

About three days ago I started to notice considerable vibrations under normal braking conditions, and especially at highway speeds.

Naturally, I looked up the symptoms and found a few possible answers: either deposits from the pads have stuck onto the rotors, or the rotors warped, or my tyres have uneven wear and the suspension geometry is misaligned.

I would just like to know what you people think is the most probable answer, and if anyone has experienced this before.

Thanks, and stay safe.

[Ghozthunter]

I had warped rotors on my g20 with only 10k miles and never tracked the car. I would image the rotors are stronger on g80 but I would definitely take it in and have the dealer scale the rotors.

[BzsBimmer]

Typically there’s pad deposits on your rotors. Rotors “could” warp but I’d be surprised.

I think the key is that you only feel under braking and at higher speeds. If tire wear or suspension geometry, you will feel it even when not braking.

I doubt the dealer will turn down your rotors as it’s a practice not really done any longer with European cars but maybe they will replace the rotors if no mention of a track event.

[barryc365]

When your come in after hot laps it's important not
To engage the hand brake, as the hot pads / rotors can get damaged, that could be one issue.

Pad deposits is quite likely the culprit though. Some hard braking might clean them off or they may need to be skimmed

[maddmatth]

Should go down over time. But you could speed up the process by doing the "bedding in" process. Basically accelerate to over 60mph, brake hard but not hard enough to trigger ABS down to about 30MPH, then accelerate and do it again about 5 or 6 times in a row to get them decently hot but not overheated.

Do not come to a stop, drive for a few minutes to let them cool back down.

If that worked, they should be smooth again.

[BzsBimmer]

Try bedding with an aggressive pad. I’ve never had success removing deposits with factory stuff. YMMV

[Ximian]

You'd have to be trying pretty hard to warp your rotors if they haven't come out of the factory already defective and warped. Also, you're not really going to find a more aggressive (track) pad to remove the deposits as they're not yet readily available. You can hone the rotor which takes a little bit of time or just replace the pads for the same ones.

Street pads can get a bit of "build up" on their surface after seeing very high heat that can contribute to these vibrations so it's better to replace them instead. Start with just the front axle.

[SwissG80]

Thank you all.
I'll try maddmatth's solution first, keep you posted of any further developments.

[The Dad]

Originally Posted by SwissG80

Thank you all.
I'll try maddmatth's solution first, keep you posted of any further developments.

Here's a link to get some understanding what you are dealing with.

[wasya152]

Had the exact same issue on my car after the track event. I was a noob and used the handbrake after getting off while the car was cooling down. Had the rear brakes replaced and all is good again.