f1wade Posted September 6, 2015 Report Share Posted September 6, 2015 Hi all, i've just got a beta rev 4t 2008, and used it a few times, but when i use the brakes more than a few times in 30 mins, they tend to lock on, and we have to take the caliper off and push the pistons back in manually. they go in mostly easy, sometimes they just wont move, until we push in the right place, which i think is due to being slightly twisted. the pads are low but not gone, as they have about 2mm left on all round. anybody know of anything that it could be? I have wondered if i could just replace the piston and seals, but if the bore is badly scored then i will also need a new caliper, but i dont want to buy pistons if i need a new caliper anyway? Quote Link to comment Share on other sites More sharing options...
mazz46 Posted September 6, 2015 Report Share Posted September 6, 2015 Fit new pads as the pistons Don't return as well on worn pads causing your problem also clean your pistons with brake fluid Quote Link to comment Share on other sites More sharing options...
worldtrialchamp Posted September 6, 2015 Report Share Posted September 6, 2015 (edited) straight from the user manual...min thickness for pads is 2mm. replace earlier to avoid what you've described. they don't wear symmetrically because they have a leading and trailing edge....once worn this causes the pistons to thrust and they get stuck...a tiny piece of grit inside will make this a whole lot worse....these calipers only have primary hydraulic seals...no dust seal..they need frequent cleaning Edited September 6, 2015 by worldtrialchamp Quote Link to comment Share on other sites More sharing options...
goudrons Posted September 7, 2015 Report Share Posted September 7, 2015 What's been said already, the 4 pots don't like too much piston hanging out of the caliper body, otherwise the pistons twist and jam. Also, make sure you've the required "play" at the master cylinders. Back the adjusters off so the levers have at least 2mm of free play before they push on the cylinders, again without this they'll jam on. Quote Link to comment Share on other sites More sharing options...
dan williams Posted September 7, 2015 Report Share Posted September 7, 2015 Had the same on my 2013. New pads didn't fix it but a rebuild did. Rebuild kit comes with pistons, seals and an O-ring. Not as bad a job as I feared. Front brake works properly now. Quote Link to comment Share on other sites More sharing options...
2stroke4stroke Posted September 8, 2015 Report Share Posted September 8, 2015 Once you have cleaned pistons etc and all is working spray the pistons and seals with silicon spray before fitting the pads. This helps prevent corrosion and also dirt getting a good grip. Quote Link to comment Share on other sites More sharing options...
slicktop Posted September 9, 2015 Report Share Posted September 9, 2015 I coated the pistons with food grade ptfe called Superlube. Which is the accepted lubrication for the same application in the marine world. Quote Link to comment Share on other sites More sharing options...
lineaway Posted September 9, 2015 Report Share Posted September 9, 2015 I coated the pistons with food grade ptfe called Superlube. Which is the accepted lubrication for the same application in the marine world. Slicktop. What marine applications have brakes? I suppose some could on the shaft? Quote Link to comment Share on other sites More sharing options...
lineaway Posted September 9, 2015 Report Share Posted September 9, 2015 By the way, Red Rubber grease is the way to go. Quote Link to comment Share on other sites More sharing options...
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