Rear brake dragging

[paganman]

Strange one this, noticed the rear brake was dragging, on start up it doesn't spin at all, I appreciate there's some resistance through the shaft drive, but even turning it by hand it's dragging.
So gave the caliper a good clean. Pumped the pistons out, cleaned with paraffin, then brake cleaner, liberal application of red rubber grease and the pistons pushed in with thumb pressure. Did the same with the slider pins. No corrosion on any part of the caliper or sliding pins.
Cleaned the old brake dust debris of the shelf the pad sits on and it's got a stainless pad pin so zero corrosion on that. Torqued it all up as per the manual and it still binds
So I wondered if the master cylinder might be the culprit, cleaned this as per the manual but found no corrosion again. Brake still binds???
Brake fluid level is spot on.
With the brake caliper off the wheel spins freely, bolt it back on and still binding?
Am I missing something obvious, or is it an ABS thing?

 

[DrFarkoff]

can you "carefully" try and move the brake pistons by finger pressure

N.B. If you press one and they are free moving the other may pop out so block one from moving while pressing the other

If you have to push really hard (near enough to be reaching for waterpump pliers to help you) then it "may be" something I have been finding with a few bikes recently Mainly the rear seals have swollen and not releasing the pistons

Even happened on my own bike

Here's the LINKY for the bits from where I get them from £16.02

Also check the that the calliper is sliding properly on the pins and that the seals are in good condition if you need the rubber bits for these LINKY

 

[Pukmeister]

It's cantilevered with only one guide pin, so it tends to bind through minute wear in the bore of the guide pin bush. Mine does it, so did the previous bike. Try putting a little sidewards pressure on the caliper without the pads in and you'll feel it bind.

 

[PatM]

I had the same problem this week- I noticed rear wheel dragging during the summer and stripped it down and teased the pistons out so as not to pop them and end up with grief , bleeding etc. This last week Ive had my rear calliper replaced at my request- therefore not covered under warrantee- but I haven't the time to muck around- being Id seen the issue a few months back- its cold now- with plenty of ice around. I also use my bike every working day, covering at least 500 miles a week- again, I didn't have the time this week and Coopers in Tun'Wells weren't busy.
The problem was that one of the pistons had corrosion and was sticking- One would return nicely.
Being an engineer-I asked for the old one back- I could strip it at my leisure, rather than in the cold of a night.
I was bored today, so went out to strip it. The pistons were just as I expected- one moved and one didn't. I used an airline to free the stuck one- plus a soaking of WD40 as it was stuck fast. Sure enough, the piston was corroded- the surface being discoloured around the sticking-spot and although I polished off the salt damage- Ind not want to put the capliper back on as I know it would stick- funny though how WD freed it up- Careful if you blow the pistons out as they come out like bullets- I used an old tyre leaver as a spacer as they will shoot out once they are freed and hurt your pinkies-

 

[Bendy toy]

Some more brake info on here

http://www.ukgser.com/forums/showthread.php?360262-BREMBO-SERVICE-KIT