mags Posted June 13, 2014 Report Share Posted June 13, 2014 Last couple of outings the front brake master cylinder has been sticking slightly on (intermittently). I can feel it with the free play in lever.... the free play increases when it sticks. Lifting the front wheel and spinning wheel sees it stop pretty quick and I can feel it dragging sometimes, when pushing the bike on concrete at home. The 2014 brakes on my wife's Beta are Grimeca branded. I'll pull it apart before next outing and see whats's causing it (internal corrosion/ machining swarf/particles???) Anything to be wary of...??? Mags Quote Link to comment Share on other sites More sharing options...
chris morris Posted June 13, 2014 Report Share Posted June 13, 2014 Remove the piston from the master cylinder and remove any gunk that has built up on it , my brakes used to stick on a bit when the piston wouldn't fully return. 1 Quote Link to comment Share on other sites More sharing options...
dan williams Posted June 14, 2014 Report Share Posted June 14, 2014 If it took a hard hit the spring in the master cylinder can be damaged. 1 Quote Link to comment Share on other sites More sharing options...
mags Posted June 14, 2014 Author Report Share Posted June 14, 2014 Bugger! It has taken a hit or two! Spring distorts/loses tension?? Any way of telling if its damaged once out? Or may look fine but damaged? Somewhere in the world would be a spring tension gauge and a setting for tension at installed length? Might just order a rebuild kit for it and put in... can't hurt especially if it comes with spring! Thanks for your input boys... much appreciated! Mags Quote Link to comment Share on other sites More sharing options...
dan williams Posted June 14, 2014 Report Share Posted June 14, 2014 (edited) On mine it looked mangled so it was obvious. Your mileage may vary. One other thing is to make sure the piston returns all the way as it's easy to adjust the lever so the piston never returns past the reservoir port. If it never opens the port the brake hydraulics become a closed system and any heat buildup that expands the fluid causes the brake to come on and say on. Edited June 14, 2014 by dan williams 1 Quote Link to comment Share on other sites More sharing options...
mags Posted June 15, 2014 Author Report Share Posted June 15, 2014 (edited) Dan, 99% sure the adjustment has free play. If the piston sticks the free play increases... thats what alerted me to the sticking in the first place. There is about 10mm movement at ball of brake lever before rod feels to make contact with piston, lever rod receiver bore, bottom. If thats a term! Hehehehe Also... if I lift front wheel and spin it stops pretty quick... then pull brake on hard and let off fast by letting lever flick out of fingers... then lift wheel it freewheels for ages by comparison. Next try or two applying brake it still free wheels but then next one or two it stays on and lever free play increases by double. Will head out in the morning for some fresh brake fluid before starting teardown. I have to start the clock with this job as its my wife's bike... once I pick up a spanner/tool she owes me big time!!! ($45anHourWink) Or its a candle lit dinner with all the trappings!!! Her shout!!! Thanks! Mags Edited June 15, 2014 by mags Quote Link to comment Share on other sites More sharing options...
dan williams Posted June 15, 2014 Report Share Posted June 15, 2014 Could be the pucks sticking in the caliper too. "Trappings", Yeah! Quote Link to comment Share on other sites More sharing options...
mags Posted June 16, 2014 Author Report Share Posted June 16, 2014 I was hoping for some "trappings" this week... Hehehehehehe Ok! Stripped it down and it looks pretty pristine in the bore and inside reservoir. Spring looks and feels great... including the small rod one. All I can put it down to was the outer "O" ring a bit grippy because it seemed dry of a smear of brake fluid??? I've assembled back together and smeared just a touch of teflon grease on the outer "O" ring. This seemed to cure the issue as it returns beautifully now. All bled up with good hard lever feel. Lifted front wheel up by milk crate and spun wheel and applied brakes 25 plus times... didn't stick once and wheel free wheels beautifully. There was a slight area of corrosion on the "C" clip that holds the piston in. Brake fluid on the bare steel I'd say... the "C" clip groove was corrosion free. There was a small burr inside and out side, from stamping it out, on the washer style plate that sits under the "C" clip. I used a 1000 grit stone and removed it.... for no there reason than it was out. Time will tell if permanently cured, see how it goes next outing? Some pics... Mags Quote Link to comment Share on other sites More sharing options...
dan williams Posted June 16, 2014 Report Share Posted June 16, 2014 Great. Sometimes you just gotta take it apart and give it some attention. 1 Quote Link to comment Share on other sites More sharing options...
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