Rear disc binding

Master cylinder , few years ago a mate with a r850r had similar issues, new pads ,pins etc didn't cure it , even put on a new braided line in case the old rubber one was breaking down and swapped the caliper from the rear of my 1150gs and it was still binding

Bit the bullet and pulled the rear master cylinder apart and it had a ridge inside caused by a partial seizure (lack of use and water in the brake fluid) , fitted and new rear m/cylinder with the original caliper and it was fine afterwards
 
Are the sliding 'pins' of the calliper free ... they seize up.

Stand at the side of your 'bike. hold the saddle, put your right foot on the calliper itself and push. It should now move inwards and be loose, with air gaps between the pads and disc. You should now be able to rattle it side to side with the hand. That's the calliper sliding on the two pins.

If you can't do this then the sliding calliper is not sliding and the pins are seized :blast

Gently pump the brake pedal (not full movement because that will move the piston seal in to otherwise unused territory) And pump the pads back to the disc. Repeat.

Sticking piston fairly rare ...

Free play at the brake pedal to master cylinder fairy common ... must have some!

Sticking calliper slider pins, where they go in to the rubber 'bellows' go dry and seize, the most common cause of rear brake binding ....

.... along with right foot resting on the pedal :blast

:beerjug:
 
Hi micky,
Yeah, sliding pins are sliding, checked them before installing caliper, greased them up, at the same time put new spring plate kit in, and retaining pin.Hopefully got a master cylinder on it's way so fingers crossed. I can normally get my head round basic spannering, but this has got me thinking. Cheers for all the responses guys.
 
Quick update gents, managed to get a rear master cylinder(the one on ebay) thanks John for the heads up on that, in the post as we speak, hopefully got out of the country before lockdown. Let you know how it goes. Cheers Steve
 
Well the new master cylinder finally arrived this morning, so going to give it a bash over the weekend. Will keep you posted. Cheers Steve.
 
Hi there gents, well finally got some time to spend on the brake prob, so first I took the pads out, wheel spun lovely, obviously no binding from brake. Soooo, took the anti squeal plates off, pads back in, much better, just a hint of binding.
Now I fitted the new master cylinder, easy enough, bled the system, 're adjusted the pedal a tad, aaaand, much better although you can feel binding still there but no where near as bad as before.
My plan now is as soon as I can get out(at this rate it might be Xmas lol) going to run her down the road as see if they are better once used a bit, touch wood etc.
Thanks for all the replies, will keep you updated. Cheers Steve.
 
It's been a while gents, but been busy messing with fairing and wireing etc, but have cracked the binding issue or should I say my good lady did. You know the old saying you can't see the wood for the tree's well she noticed the caliper was very slightly not square to the swing arm, so took it off and noticed the sliding pin on the caliper was bent !!! Swapped the old pin over, and problem solved, no binding. Bit of a bugger as ordered a new disc and pads the night before, oh well.
Thanks for all the replies.
 


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