D Linden :) Posted October 17, 2012 Report Share Posted October 17, 2012 Today my rear brake (HS33 05, Water bleed) started playing up At first the piston in the lever body got stuck so I fixed that by spraying it with GT85 and a new bleed Once I had finished bleeding i pumped the brake a few times and the piston in the cylinder with the bleed bolt had stuck right the way out but was still functioning the other staying normal I then sprayed it with GT85 and it went back to normal A few hours later it started doing the same thing, bleeding isn't helping and now the piston in the lever body is retracting very slowly, could there be a leak? Any one know whats wrong/saggest anything to fix this? Cheers 1 Quote Link to comment Share on other sites More sharing options...
trialsiain Posted October 17, 2012 Report Share Posted October 17, 2012 Not sure but maybe lever piston oring has expanded causing it to come out slowly you can get new ones on tarty for £1. Quote Link to comment Share on other sites More sharing options...
dann2707 Posted October 17, 2012 Report Share Posted October 17, 2012 Looks like the water bleed has swollen the piston in the master cylinder. Remove the piston and lightly sand it after gently removing the O-ring. Quote Link to comment Share on other sites More sharing options...
trialsiain Posted October 17, 2012 Report Share Posted October 17, 2012 How does water do this Quote Link to comment Share on other sites More sharing options...
dann2707 Posted October 17, 2012 Report Share Posted October 17, 2012 (edited) The nylon (I think) piston absorbs it and swells up Edited October 17, 2012 by dann2707 Quote Link to comment Share on other sites More sharing options...
D Linden :) Posted October 17, 2012 Author Report Share Posted October 17, 2012 Ok il give it a try, should sanding be enough or should I replace the oring as well? Quote Link to comment Share on other sites More sharing options...
JD™ Posted October 17, 2012 Report Share Posted October 17, 2012 Sanding should be enough, just don't take much off! Quote Link to comment Share on other sites More sharing options...
trialsiain Posted October 17, 2012 Report Share Posted October 17, 2012 So is it not a good idea to water bleed then ? Quote Link to comment Share on other sites More sharing options...
Martin Reynolds Posted October 17, 2012 Report Share Posted October 17, 2012 So is it not a good idea to water bleed then ? Water doesnt have as good of lubricating properties as oil, and can cause the piston to swell up as mentioned, but its a hit and miss thing. In one brake system it could work fine, in others it can cause trouble. Quote Link to comment Share on other sites More sharing options...
trialsiain Posted October 17, 2012 Report Share Posted October 17, 2012 Is there anything you can add to it to stop this Quote Link to comment Share on other sites More sharing options...
dann2707 Posted October 17, 2012 Report Share Posted October 17, 2012 Antifreeze Quote Link to comment Share on other sites More sharing options...
trialsiain Posted October 17, 2012 Report Share Posted October 17, 2012 But does that make it just feel Like normal fluid Quote Link to comment Share on other sites More sharing options...
dann2707 Posted October 17, 2012 Report Share Posted October 17, 2012 Nope. Still as viscous as water. 1 Quote Link to comment Share on other sites More sharing options...
wilf Posted October 17, 2012 Report Share Posted October 17, 2012 Ive got a Maggy with a swollen piston. Going to get daddy to have a go at making stainless ones Quote Link to comment Share on other sites More sharing options...
dezmtber Posted October 18, 2012 Report Share Posted October 18, 2012 wow wow wow. its st85 that is killing your seals. the spray lube has white spirit in the mixture to help it penetrate cracks and into rusted bolts. this will dry your rubber/nylon seals. what you need is a silicon based spray or even better o-ring lube to free up the pistons on your brakes. if you cant get either of those use mineral oil on the seals. only ever use brake cleaner and silicon based oils (or the oil used in the system) to lube your brake pistons nothing else it will likely cause the brake to fail Quote Link to comment Share on other sites More sharing options...
trialsiain Posted October 18, 2012 Report Share Posted October 18, 2012 i have silicon gun oil will that work ? 100% silicon spray Quote Link to comment Share on other sites More sharing options...
dezmtber Posted October 18, 2012 Report Share Posted October 18, 2012 it will help give it go. all silicon spray lubes are simmilar in that they contain silicon, though i would say gun oil would be more aimed at corrosion protection rather tham lubrication. so may contain other chemicals to help corrosion rather than lube Quote Link to comment Share on other sites More sharing options...
the mysterious leemur Posted October 19, 2012 Report Share Posted October 19, 2012 i have silicon gun oil will that work ? 100% silicon spray Do I sence a 'softer? 1 Quote Link to comment Share on other sites More sharing options...
stunt man t Posted October 19, 2012 Report Share Posted October 19, 2012 if its not bleed with what the brake was designed to be bleed with, dont cry when it goes wrong Quote Link to comment Share on other sites More sharing options...
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