1994 850 T5 - Rear Brakes Heavy Vibration At High Speed

[Boxman]

I've seen a lot of topics about rear brakes and vibration, all fixable with 'shims', but those are all at LOW speeds.

I have heavy vibration coming from the rear brakes at HIGH speed.

I have Brembo disks and EBC Red brake pads. Initially there was no vibration, but after a few K miles I had to take the disks off (to fix my handbrake) and put them back on. Since then, I have heavy vibration coming from the rear while braking.

At first I thought this might be because the disks were not properly aligned - so that the brake pads would slightly differ from the 'path' it has etched in the disk. But the disk feels smooth, so this I think can't be the main cause.

I did not replace the bolts with new ones, as they are just regular bolts and not stretch bolts, and only have been on there for a few K miles.

Anybody have any idea what could be the cause of this vibration?

[Pj3r]

There are (probably) two small bolts in the disks. Countersunk in there. Did you tighten them?

Also, if a disk isn't straight anymore, you probably wouldn't be able to feel that. Secure a screwdriver to a point on the disk and turn the disk (try thinking of a lathe, where your screwdriver is the bit). If it hits on one side and is not on another, it's bent.

This might happen as easily as driving through a puddle of water when the disks are hot (happened to me once)

Check if the lead (for balancing) is still on your wheels. If not - rebalance. If so - rebalance to make sure it's okay.

That would be where I'd begin.

[DevenlnNY]

What I see mainly on any car utilizing the "hold down" type bolts/screws, some people tighten them up and it actually causes the rotor to not lie flat on the hub assy. On another note, anytime you remove the rotor, make sure the hub and the underside of the hat on the rotor are free of rust or any othger debris. GL