I have an MG Midget (2ltr Zetec - not related) and have a strange problem that if I have been travelling for some time (e.g. on the motorway) and brake, it pulls to the left but then, if I brake again, all is good. Any ideas?

Yeah - one caliper (right hand side, probably the front) is seizing slighty - it's happening while you're driving but not using the brakes.

After the first apply, when the brakes pull, the seizing eases off and it works fine again for a while. Until you don't brake for a while - then the problem repeats.

Best way to relieve the issue is replace the offending caliper.

Indeed. But I would be buying a seal kit and doing both calipers. Not difficult as long as the pistons are not seized solid! (which yours are not by the sounds of it)

Replace the caliper seals on both sides. Also remove and grease the pistons. Its a simple job and cheap to do.

And use red brake/rubber grease. Copper grease is NOT suitable for seals/pistons/bleed nipples etc

I'd replace rather than re-build but that's your call. However...

NEVER use a normal Mineral Oil based lubricant (grease, oil, WD40 etc...) on brake caliper seals.

The rubber they are made from will not tolerate it and the seal will gradually deteriorate until your brakes fail!

IF you want to lubricate them as you rebuild the caliper use the DOT brake fluid.

I would, and have done, replace the seals, and pistons in the front calipers,

As long as everything is spotlessly clean, and rust free, the brakes will work 100%

I did it myself on my 7, as had similar issues, and the brakes, and driving were perfect afterwards

steve

Thank you guys :-)

I used bigg red who supplied me with stainless steel pistons and seals. In theory the pistons should not rust and pit like the originals, great for a car that is standing over winter...

[Edited on 20/2/20 by Bluemoon]

I had similar problem and did as the other said and refurbed the calipers my self.
Brought a kit for the seals and by accident saw a company selling st.steel pistons on ebay which were fantastic quality.
Use a car air compressor to remove the old pistons.

brake disk runout / slight warping, or failing wheel bearings can also cause symptoms like this.
(they knock the pads back a tiny bit further than the other side)

If its a single piston caliper on sliders I had similar years ago. Turned out the slides were worn (not seized),causing the caliper to cock and jam occasionally. Wasn't obvious at first, as every time I had the wheel off it all seemed free.