XSeries-forum

Good grief get your thinking caps on..
Just drove the car for the first time above 50mph after the mot. Absolutely crazy vibration through the whole car like driving on a cattle grid after 50mph and upwards. Steering wheel shaking badly too. I slowed down to 50 to keep it drivable.
Anyway, after about a mile or two it suddenly stopped and was all smooth again..
Had to drive through Letchworth so slow again until the return along the A505 and all was smooth still. What is that all about?
Any ideas?

Possible sticking brake caliper?

This was how my X6 behaved, twice. In both cases a front calliper had seized such that it wasn’t fully releasing and was dragging against the disk. It would come and go but after a couple of weeks in each case, had to be dealt with.

Simplest way to check is pull over when safe and feel how warm the wheel hubs by the brakes are. If one is much warmer than any others then that’s the problem corner. Don’t touch a disc!

My front right went first and about two-years later the front left did as well. For the first one, I replaced both front discs and pads at the same time. The LHS one was so bad that the brake unit itself almost seized on the way to getting it repaired. The disc was just starting to show a blue tinge!! You may also be able to smell ‘hot brakes’ - that sort of burnt clutch smell from years of old…

If all four corners are the same temp then the issue is elsewhere, but given you’ve just had the brakes tested as part of the MOT that would be my first thing to look at. The seals stiffen and prevent the piston retracting properly. It’s an easy fix (if you are so minded).

A sticking caliper did cross my mind - front nearside has been a bit stiff in the past.
I've got a rebuild kit somewhere so that's possibly a job for tomorrow.
Thanks chaps.

When I had a sticking caliper you could see one side the wheel had much more brake dust than the other so an easy way to tell

Oh yes it's sticking.
I pumped the piston out as far as I could without it falling out., peeled the boot back and it had rusty bits on the piston. I've cleaned it up as good as I could, sprayed some lube around it the pumped it in and out several times until it felt free ish.
We will see until I get a new caliper or rebuild it.

Always rebuild mine you know it is done right that way but i am old school and had to do it that way.
Get my parts from biggred but they have an eBay shop as well and can sometimes be cheaper on there.
https://www.biggred.co.uk/

Gosh. Had the massive steering shake again this morning. Of course I didn’t swap the caliper or fit the Biggred kit when I last posted about it…
Sort of forced into it this evening as it was barely drivable. Nearly 200psi of air would not pop the piston out. It was nearly there but just wouldn’t come out until I got a chisel and hammer to it. All cleaned up and new seals / piston installed.
Should have done it months ago.

You sound very much like me.
I get the parts straight away but take months to get round to fitting them sometimes.

And check this out - the average mpg for the journey I’m doing at the moment has gone from 19.7mpg to 23.2mpg. Just shows what a dragging brake does.

That’s quite a change. As you say a lot of energy being lost to heat and friction.

That could add up to a lot of ££££££.