Vibration when braking M5

[Singh911]

I bought a 2012 M5 from BMW 3-4 weeks ago. The car has 16k miles on it - and its fabulous.

When i test drove the car prior to buying it, upon braking from motorway speeds say 60mph, the steering vibrated quite a lot.

During their prep work, the dealer said that the vibration was due to the front discs and pads and put new ones on the car before i picked it up.

I have done around 500 miles and the vibration is still there - at first i thought it was just in my head but its definitely there, if i let go of the steering you can see it vibrate on braking. Its not there all the time. Its not there when you brake from low speeds up to 40mph either. Its only there when i brake from 60mph.

I have called the dealer and told them that the issue that was there before i bought the car is still present. The car is booked in on the 15th.

I'm thinking it can't be the discs or pads, these are brand new.

Could anyone suggest what this is - or has experienced it?

I'm thinking it could be something load related ie only apparent when braking from speed? So control arms? Bushes? Ball joints? Could it even be a rim thats not true round but wouldn't that be apparent at all speeds?

Cheers

[W8PMC]

Could it simply be the tracking's out of the wheels are unbalanced?

It's recommended to get the cars laser aligned every 12mths so on a 3yr old car it may not be a bad idea.

[Singh911]

Could be - I did insist they do a full geometry before i took delivery of the car, and they told me that they had. I will reiterate this when it goes in on the 15th.

Cheers

[AW10]

Can you check that the discs were actually replaced? It should be pretty obvious - their surfaces should be very smooth with virtually no signs of wear, virtually no corrosion on the rotor bells and no ridges on the outer edges. I bought an AUC M5 a few years back and the numpties put new pads on knackered discs - they then ending up paying another dealer to replace the discs and the pads. False economy!

[Pip1968]

I would say sticking calipers if it was not for the fact that the car has so few miles.

Did you bed the discs and pads in correctly ie a few hard stops from different speeds? Maybe you have left a deposit or smear on the discs.

Best of luck.

Pip

[Raify]

I had an identical problem, but on an E39 with loads more miles.

It was a worn front control arm bush. Seems unlikely that worn suspension parts could be a problem after only 16k miles though. Could a similar symptom be due to suspension issues? (Geometry etc).

[Schermerhorn]

If the brake discs and pads are brand new (this is easy to physically check) and the tracking has also been done then it could be a control arm issue. I believe there a few on the F10 models.

Also check they actually did replace the brake discs and not skimmed them using a brake lathe.

When prepping AUC cars many dealers (not just BMW) clean up existing brake discs on the lathe, stick new pads on and the new customer does not have a clue.

Nothing is wrong with skimming the brake discs - it can be very effective and work very very well - but if the discs were knackered to start with and warped then it is pointless.

[Singh911]

I have no real way of knowing how thorough they were. The discs looked new. I insisted on a geometry and they said they did it. I did break in the discs properly and made sure i cooled down the discs before stopping.

The car goes in on the 15th, I am uncertain whether to make suggestions to them (ie control arm, rims, warping) or to leave it to them to look at it and resolve. I am never sure if it gets their back up if a customer tries to tell them what to look for when they're meant to be the experts.

Either way, im going to stand my ground and insist its covered by them.

[Gruber]

It could be rear discs. Or a knackered tyre deforming under braking. Or the new front discs not having been fitted properly.

Best to let them sort it out and don't let them off the hook.

[ecain63]

My E61 M5 had brake wobble. Thought the discs were new but they weren't, they'd been skimmed down. Only way to check is with a gauge. Read the tolerance from the disc bell.

[Singh911]

The car is with the dealer and they reckon the discs are warped - so they're replacing them. They supposedly did that pretty delivery to me too. I can't think they put new ones on previous delivery and are doing so again now. The hubs look new and the discs looked new when 8 bought the car. Lets see if this fixes the issue.
I assume the running in for the discs is as for other cars in a series of braking from 60 to 20 with cooling off before I stop?
cheers

[JMBMWM5]

Singh911 said:

The car is with the dealer and they reckon the discs are warped - so they're replacing them. They supposedly did that pretty delivery to me too. I can't think they put new ones on previous delivery and are doing so again now. The hubs look new and the discs looked new when 8 bought the car. Lets see if this fixes the issue.
I assume the running in for the discs is as for other cars in a series of braking from 60 to 20 with cooling off before I stop?
cheers

I would NOT run-in the disks/pads, just drive respectively on the brakes for 300 miles, they will bed themselves.

[Singh911]

Thanks for that. Is this so that the any anti squeal/anti rust film can be worn off and the brakes are polished? Should I bed the brakes in after that initial period or is the bedding in 60-20 several brakes entirely unnecessary.
Cheers

[JMBMWM5]

Singh911 said:

Thanks for that. Is this so that the any anti squeal/anti rust film can be worn off and the brakes are polished? Should I bed the brakes in after that initial period or is the bedding in 60-20 several brakes entirely unnecessary.
Cheers

Personally I have had all the "M" cars, last two were LCI M5 and this M6 GC CP, i have never bedded any brakes in and never ever had brake squeal.
Your choice.