Hi there. Was practicing today and the rear wheel started to lock up. I thought it may just be the high temperatures and me using the rear brake a lot or that the connceting push rod into the master cylinder did not have enough free play. So I unbolted and adjusted the push rod to give it a bit more free play but the brake still binds. Took the bike home as it was unrideable and had a quick inspection. I bled the system and all appears normal with no aor in the fluid but it continues to bind. I think there may be a slight squelching sound coming from the master cylinder when the pedal is pushed but I dont know if that is normal. Could it simply be that the pistons are a bit siezed up in the calipers ? Any advice would be appreciated before I go ordering parts. The bike was fine when I rode it on the weekend so there hasn't been a gradual build up of a problem. Gareth

Gday, If you have freeplay at the lever it would most likely be a seizing piston. Double check the piston in the master cylinder returns fully to the circlip with some free travel first though. That may save a heap of angst when you go to re-bleed the bloody thing after a rebuild... If the pistons seem free (check before pulling them right out) it may also be a bit of rubbish blocking the tiny transfer port in the master cylinder. The only way to get into that is to dismantle the master cylinder and blow it clear with an air line. Good luck.

Cheers,

Stork

Try putting in some new pads or swap them with the front ones and see how that goes.

If your pads are quite low the pistons are out pretty much all the way, new pads

normally sorts it.

Thanks for all your responses. The pads have about 3mm wear left in them so may need changing. I still think the pistons are a bit seized. All four do not move simultaniously. In fact one doesnt move at all. Spoke to lampkins and they said use wd40 and just spray, push them back, spray, push them back until they free up. One of them feels bloody stiff. Any more advice ? How easy are the pistons to get out, clean properly and then put new seals on them ? I know drum brakes were bad but at least they were easy to maintain !!!!!

I use duck oil, spray and gently brush with an old tooth brush. Blow the crap away with compressor and repeat till clean and moving freely.

(use WD40 if thats what Lampkins recommend)

Edited June 4, 200917 yr by B40RT

I use duck oil, spray and gently brush with an old tooth brush. Blow the crap away with compressor and repeat till clean and moving freely.

(use WD40 if thats what Lampkins recommend)

Cheers for that. They should all move in unison though shouldnt they ?

Gday, in theory they should but in practice they might not. I wouldn't use WD40 near any brake parts as it contains petroleum stuff, which will hurt the rubber seals long term. If you want to try cleaning pistons without removing them (not a bad idea actually) just use some detergent and a toothbrush. I do this before fitting new pads on pistons that are out to remove any rubbish before pushing the piston back in for the new pads.

Stork. That seems like a good idea. I am off work tommorow so I will have a whole day to dedicate to the calipers. I have done a bit of reading and one idea that sounded good was to restrict the movement of the piston that moves freely by maybe a small clamp and this in effect should force the other ones to move. I think i just need to have a good fiddle with it to free them up. I will let you know my outcome. I may have welded on the rear end of my ty175 by the end of the day if I get really wound up !!!!

Hi Fella,

Had LOADS of trouble with the rear brake binding on my 2001 Rev3. It's the 4-pot caliper and there have been three issues:

• Grit in the master cyliner transfer port
  Binding pistons
  Uneven pad wear caused by the above. If this occurs, the pads can form a wedge which makes them sit askew on the pins. You'll know if it's this as rolling the bike backwards releases them.
  

They do seem susceptible to sticky pistons, but all calipers do to some degree or another. I have spent a lot of time cleaning the pistons (I use hot soapy water and a toothbrush). Get some small blocks of wood of various thicknesses so you can isilate the movement of at least one pair (if you have 4-potters like me) and pump out the remaining pair. A small G-clamp suitably shaped in the grinder can then hold the 3rd piston in so you can work on one at a time. This has just about kept me rolling, but I need to service them properly with new seals and pistons. I am, however reluctant as I know I'm in for a world of pain getting air out of the system when I do this!

Good luck

Graham

Right then. Thanks for all your advice. After a lot of pumping and clamping and bleeding and more pumping all four pistons now seem to be moving. Ive bought new pads to fit on re assembly. Do you think there would be anything gained from using a rubber friendly silicone spray to coat the pistons before putting the pads in ?

Cant do any harm. I try to always blow the calipers dry with an air gun.

Really usefull for cleaning off the chain as well.

Bike up and runnng again. New pads fitted. Pistons moving freely. No evidence of binding. Thanks or all your help. Until the next time !!!!!

Gaz