Brake Judder!

Hi
A few months ago I was suffering bad brake judder it happened at all speeds,so I replaced the front discs, problem solved I thought,no more brake judder but the ABS lamp would not go out.I discovered my o/s/f sensor was u/s so I replaced it and now my brake judder is back, what's going on????

ABS engaging when it shouldn't perhaps?

Bit of an odd one really...

This post has been edited by Ciaran on October 18, 2007 11:14 pm

What did you remove and replace to do the job?

Are your suspension wishbone bushes worn so that they reset themselves differently when you put wheel to ground again?

Did you fit new disks?
Disable the ABS and see if the problem is still there.
Check the calipers and the condition of the brake pads.
Brake judder can be caused by inbalance of the wheel, but if you say at all speeds . . . hmmm

This post has been edited by Jan-hendrik on October 19, 2007 11:25 am

The discs are new from Halfords (£60) I used the same pads,I'd just replaced them to help with the judder.

When the judder first happened it was at all speeds right down to a stop,not really a judder at low speed more like a classic warped disc, now it's only at motorway speeds. She sailed through the MOT last week and the tester was very thorough.

The annoying thing is the old discs showed no visual signs of being buckled but replacing them cured the low speed problem.

Can I disable the ABS without touching the ECU ? it's tucked up behind the radiator and a pretty tight fit.

thanks guys

The tolerance for disk run-out is a mere 0.05 mm, so distortion is not visible without very accurate measuring equipment.
The ABS can be disabled simply by removing fuse F3 in the fuse box in front of the battery. This 30A fuse is located on the far right in the top row standing in front of the car, if everything is still original
BTW, I don't think MOT testers check disk run-out.

I figured the brake test might show the ABS misbehaving or maybe excessive disc run-out .

Hi Bosscat

I bought an XM a few months ago with a couple of known faults, gentle steering wander and front brake judder at all speeds. When I drove it the 150 miles home sure enough the steering needed a regular gentle nudge on the wheel to keep it straight but of the brake judder no sign at any speed. I rang the mechanic who sold it to me to ask about the brake judder and was told it had moved to the Merc he was now driving. Then he explained why. I had refused to drive the XM away until I had put decent matched tyres on it so I took a spare set of steel wheels with good tyres down and put them on the XM but wanted the original alloys as well. He felt I was being a bit pernicity about tyre condition and asked if he could have the best two tyres off the alloys and I said fine by me because I was going to scrap them anyway. He put the tyres on the front of his car and got exactly the same brake judder problems as they had caused on the XM when he was using that. He concluded that a previous owner had left the XM standing on nearly flat tyres while it was SORN.

Try swapping your wheels front to back and see if your brake judder alters.

Regards

XMexc

This post has been edited by xmexclusive on October 19, 2007 10:29 pm

Hi XMexc

It's funny you should say that because not long before my judder problems started I swapped the the wheels front to rear.

cheers pvc

This post has been edited by bosscat on October 20, 2007 05:48 pm