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Full Version Wobble under high speed braking

Club XM Forum > XM General Issues
BrendanM
I have a 1996 series 2 XM 2 litre petrol injection estate with Bendix ABS.

When I bought the car it seemed OK on the test drive. However on the motorway at 70mph there was a judder or wobble when braking. When I got home I replaced all 4 wheels from my other XM but the judder was still there.

From reading previous post I have come up with a list of possibilities.
Wear in the wishbone bushes, faulty drive shaft, disc brake rotor faulty or misaligned due to dirt behind it.

If the car passes the MOT I will start investigating the disc rotors.

Are there any other possible causes for this problem?
rockman
Wishbone bushes are the most likely suspect, easy to check, just jack the wheel off the ground, yank the wheel sideways and look at the bushes for movement.
Zaphod
I'd also check the run out on the brake disc (not rotor we are NOT american) this quiet often occours on ABS equiped cars
Jan-hendrik
QUOTE (Zaphod @ )
I'd also check the run out on the brake disc (not rotor we are NOT american) this quiet often occours on ABS equiped cars


I think the front brake discs were prone to warping. On my 1995 XM, no longer in my possession, the front discs were replaced under warranty after only 20k km. I replaced them again at 40k km mad.gif
Dieselman
Most of the time disks don't warp but suffer with friction material deposits causing uneven braking.

As a test drive with your foot planted on the brake and accelerator to get some heat into the brakes, then test the brakes again.
If things are better give the disks a good scrub with a hard abrasive, such as a wet stone.
BrendanM
I found that the two small small bolts with countersunk heads that hold the disk onto the hub were slightly loose.

I assumed that the five wheel nuts would keep the disc pressed flat against the hub but that was not the case for my discs.

Luckily the simplest and cheapest solution worked.

Thanks for your suggestions.
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