keithns Posted January 2, 2013 Report Share Posted January 2, 2013 Hi I have a couple of problems with the rear brake 1) when it's wet or wet and muddy it doesn't work, is this the pad material or what ? any suggestions or make of pads that work wet, muddy or dry, I have tried Galfren, Galfer and EBC. 2) to get the caliper pistons to push back I have to open the bleed nipple, is this normal ? (I don't have to do this on the front caliper), surely when the pistons are pushed back the fluid should just go back to the reservoir, any ideas why ?. Keith Quote Link to comment Share on other sites More sharing options...
naichuff Posted January 2, 2013 Report Share Posted January 2, 2013 No the pistons should return without opening the bleed nipple Check you have free play between the master cylinder and the peddle The master/c may not be returning fully ( mud ingress) as this can hold the pressure on this could be partly why you have poor brakes Quote Link to comment Share on other sites More sharing options...
lineaway Posted January 3, 2013 Report Share Posted January 3, 2013 I have heard of this in other brands with formula brakes, any opinions? Quote Link to comment Share on other sites More sharing options...
grumpyget Posted January 3, 2013 Report Share Posted January 3, 2013 Try removing the rear brake master cylinder, let all the old fluid drain away from the reservoir, clean externally best you can, then remove the rubber boot and circlip and push the piston and spring out. Give it all a really good clean. Might be best to get a new Beta seal/piston replacement kit (only a few quid from John Lampkin online - next day delivery) Ensure the cylinder internally is really clean, cover the new piston assy with brake fluid and refit with the new spring, circlip and rubber boot (supplied in kit). Refit to bike ensuring there is a bit of pedal free play (pedal lets the piston return to open position on its own). Top up fluid reservoirwith new brake fluid and bleed till you get all the air out. If you have trouble bleeding it, get a surgical syringe and a short length of clear pipe attached to bleed screw and draw the fluid through then lock the nipple. You should have a good brake pedal. Probably best to put some new galfer pads in and make sure there is no oil or grease on the disc. If you spray WD40 or anything like it near the rear disc you can contaminate the disc without knowing. Hope this helps.. 1 Quote Link to comment Share on other sites More sharing options...
pindie Posted January 4, 2013 Report Share Posted January 4, 2013 +1 Quote Link to comment Share on other sites More sharing options...
myzeneye Posted January 5, 2013 Report Share Posted January 5, 2013 +2 Follow grumpy gets instruction and you'll be sorted. Seals in master cyl swollen in my opinion..... If you remove the flat o ring seal, they very often have crap underneath them causing them to swell and not move freely or even stick completely. Remove push rod, remove rubber boot, remove circlip , piston/plunger, remove o ring seal clean and replace... Reassemble, refill and bleed. Job done Quote Link to comment Share on other sites More sharing options...
myzeneye Posted January 5, 2013 Report Share Posted January 5, 2013 There's less in there than you think, it's very simple.... Don't be frightened to get stuck in! Quote Link to comment Share on other sites More sharing options...
keithns Posted January 11, 2013 Author Report Share Posted January 11, 2013 Many thanks for the info, have stripped the the master cylinder and cleaned it out, although it appeared to be OK, have reassembled it and it works fine, caliper pistons seem to be free but still difficult to push back without cracking the bleed screw, anyway have fitted some new EBC pads, hope to get out this weekend and see if problem is cured. The caliper pistons are free but I think they could be freer, so have ordered some new seals so that I can strip the calipers next week. PS grumpyget I have in the past accidentally sprayed a disc with WD40 and that definately stops the brakes from working. Keith Quote Link to comment Share on other sites More sharing options...
tltel Posted January 11, 2013 Report Share Posted January 11, 2013 Have you got free play at the brake pedal? there should be a couple of mm free play on lever, you can adjust it on the push rod attatched to the pedal. If the rod is touching the piston the pads may not move back easily. TLTEL Quote Link to comment Share on other sites More sharing options...
keithns Posted January 15, 2013 Author Report Share Posted January 15, 2013 Saturday finished off trying to sort rear brake, new pads and changed fluid, eventually got a good lever, what a pain to bleed the caliper, had to take it off and hold it above the master cylinder to get the air out, thought I had cracked the problem as brake seemed to work fine on the drive. Went to local trial on Sunday, first section I got to with a big downhill it didn't work again, but after getting a bit of mud etc in it and riding along with my foot on the pedal it seemed to bed in. Then I injured myself and had to retire after 2laps. After I got home and washed the bike it now appears to be not working again, so back to the drawing board. Quote Link to comment Share on other sites More sharing options...
pindie Posted January 22, 2013 Report Share Posted January 22, 2013 The travel needs to be at the actuation rod not nescessarilly the lever as wear in the joint may make you think you have te right amount. Are your pad pins worn? When you re build the calipers you need a smear of copper grease on the pins and pad backs. Quote Link to comment Share on other sites More sharing options...
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