Are my brakes ok? [2007 E92 M3]

[sylonien]

Um not sure if its the same or not, but its brake related?

Stupid question, what's wrong with them? They don't feel they bite that well either, little spongy. And that's just from normal town driving. Feels like it doesn't stop very well at all. Not snappy or powerful.

You can feel the grooves and bumps if you touched them with your finger.
The worse are the rear ones and look like shit.

iDrive says 10-20k miles left. Is that the pads or discs?

And its a 2007 E92 M3 btw

[mlhj83]

I'm 100% certain that your discs are way below their minimum thickness - I stake my life on it for that matter! Time for new discs all round. Also, your brake fluid probably needs topping up or changing. Your pads' surface will be better examined when the discs come off. Cotswold BMW do better deals on OEM parts compared to anywhere else - give them a call.

Your iDrive brake life indicator is only for the pads, and are calculated from various parameters such as how hard you brake, how often etc., but not an actual measurement. Basically, someone could put worn-out pads and reset the indicator, and an oblivious person would be none the wiser.

[sylonien]

Hmm that's annoying.
Well it is concerning me hence the thread.

Since they feel well under powered at the moment.

Expensive man...

[W///]

Rotors look shot to me. Yes it's an expensive job, but you gotta pay to play with these M's.

[apecush]

you left your car for way too long without driving it in a corrosive atmosphere and your brakes rusted. a lot. simple as that.

replace rotors, pads, and fluid.

[mlhj83]

Originally Posted by apecush

you left your car for way too long without driving it in a corrosive atmosphere and your brakes rusted. a lot. simple as that.

replace rotors, pads, and fluid.

No, rust has got nothing to do with it - rust on the friction ring of the discs gets rubbed off when brake pads make contact; it's the discs that have worn below the specified minimum thickness, which is the main problem. Pads should otherwise be fine as they still have a decent amount of pad material left and can be properly bedded in with a new set of discs. Brake fluid level and condition will definitely need to be checked.

I regularly do pad swaps, thickness measurements and fluid changes for each track day, so I'm very familiar with the brakes of the M3.

[sylonien]

Um it was already like that, slightly less severe when I got it half a year ago.
I've been driving it every single day since getting it her, day and night.

So its not rust.

[apecush]

Originally Posted by mlhj83

No, rust has got nothing to do with it - rust on the friction ring of the discs gets rubbed off when brake pads make contact; it's the discs that have worn below the specified minimum thickness, which is the main problem. Pads should otherwise be fine as they still have a decent amount of pad material left and can be properly bedded in with a new set of discs. Brake fluid level and condition will definitely need to be checked.

I regularly do pad swaps, thickness measurements and fluid changes for each track day, so I'm very familiar with the brakes of the M3.

taking your brakes below minimum thickness does not chew a rusty groove in the friction surface, nor does it corrode the chamfer around the drilled holes in the rotor. Mine are near minimum (thanks to track pads) and look absolutely nothing like that.

[mlhj83]

Of course a disc below minimum thickness has nothing to do with rust on it, but you stated that poor brake performance was due to rust, which it isn't.

I stated that the poor brake performance is due to the disc being badly worn and also worn to below minimum thickness. Surface rust on the friction surface is of no consequence to disc brakes as they eventually get cleaned off upon application of the pads, which I'm sure you already know.