Disc vibration

C

cj10jeeper

Lifer
 Lichfield, England
Here's an odd one that you may be able to throw some light on.

Six weeks back I upgraded my brakes to the larger front discs with 330 calipers, carriers, etc. replaced all discs with new EBC Ultima's and a set of greenstuff pads. Correctly cleaned and seated the discs and hub faces, bedded and ran them in as per book.

So here we are 500 ish mikes on them, driven carefully as I've not had any opportunity to really use them, other than the cruise of a few weeks back and now they vibrate like a washer on spin. Mainly via the brake pedal.

Today pulled everything to bits. All bolts and fixings secure, no run out on the discs, perfect even wear (well more of a shine as they are unmarked). All wheels rotate freely and no tight spots.

Going in for her full geo set up Tuesday but prior to that any thoughts on the cause?
 
You might want to read the linked article and see if anything sounds familiar:

http://www.stoptech.com/tech_info/wp_warped_brakedisk.shtml
 
My initial thought was warped discs but i'd have expected you to say steering wheel wobble under breaking plus you've said there's no run out
"Mainly via the pedal"??
This would lead me to think that maybe you've got air in the brake system still so needs bleeding.
Does it feel like the ABS is working?
I'm not sure in the details on how the ABS system works on the BMW's seeing as this is my first but did you drain the brake fluid out completely? emptying the system completely or getting dirt in it can upset ABS actuators causing the solenoids or motors inside to behave erratically.
 
TO//M - Interesting read thanks. Dispels the myth of brake rotor warp or distortion. I'll have a good look at the rotor surface and have a crack at rebedding them.

Tom14S - Yes - I've crudely checked run out and there is none. Plus the rotors are so new and the article above dispels this. I'll bleed the brakes a little more, but no way did I allow it to become empty or indeed overpump to bleed them :) . I'm sure the ABS is not involved in this issue
 
There are a few caveats in that article, though, jeeper. Mine *were* warped-I had taken the car in for a tire rotation and this "shimmy" developed soon afterward. I think they overtightened/mistightened one of the front wheels. A relatively cheap set of Brembo rotors cured it rather quickly.

As the others are suggesting, check the fluid, joints, etc. I may be something very simple. Good luck. :thumbsup:
 
Right I found another hour to sort this out and it turned out fairly simple.

In my search I had pulled off the front rotors and focussed on them, but this time went deeper on the rears thinking and prompted by comments. As the vibnration was pedal not steering wheel that pointed to rears. Once removed I found the culprits. A pair of neat pad imprints on the inside of the rear discs, with inevitable pad build up in that area. Hidden by the shields, but nonetheless there.

I'm not in a blame culture so I'll take responsibility, but I reckon Mrs CJ did a bit of decent braking then parked it in the drive with the handbrake on. Something I never use. :headbang:

Cleaned them off with a flat bed scraper, reassembled and took it for a renewed cycle of warm up and bed in brakings. Ran for 5 miles without touching the brakes and now we're back to perfect. :thumbsup:

I'm pretty sure I got it soon enough not to let any changes take place in the disc, but need to keep an eye on it.

So there we are - thanks all. :thumbsup:
 
Great!!!

In her defense, though, I always use my handbrake but I don't run it hard and brake hard before parking for the night. :thumbsup:
 
Hey - I'm not really blaming her. My life expectancy would become too short to do that and the list of domestic projects would increase :!:

Just shows that despite me knowing my way around cars I missed, with hindsight, the rather obvious and equally with these much bigger brakes on and prior experience of braking on stock, I probably did not get them hot enough the first time I bedded them in.
 
Err correct me if i'm wrong, but!

the had brake uses internal shoes in the brake disks.

the rear pads are not used in the handbrake mechanism on a current BMW TMK. :driving:

Dario
 
dario said:
Err correct me if i'm wrong, but!

the had brake uses internal shoes in the brake disks.

the rear pads are not used in the handbrake mechanism on a current BMW TMK. :driving:

Dario
Click to expand...

Yes - you're of course spot on and I should know better than type that :oops: I'd spent 30 minutes frickin about adjusting the handbrake shoes up again after removing the discs and had them on my mind when posting, after bedding them in and being overjoyed at solving the problem. :oops: :oops:

Just a simple case of hot pads being held on the rotors and imprinting.

Makes me wonder if the inner faces of the rears get hotter with all the cover around them as the rest of the faces were just fine.
 
i think i've warped my disks, bit of steering wobble under braking now. I just need the excuse to put on bigger brakes as well :roll:
 
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