Tuesday Posted May 20, 2011 Share Posted May 20, 2011 Couple of tips for getting seized brake pistons out of calipers, add yours. Opposed piston brake calipers, Oh yes. Usual story, piston on one side gums up and the other one does all the work. Time to split the caliper and get both pistons moving freely. The stuck piston tends not to want to move and offers little material to grab onto. 1/ Before caliper dis~assembly , remove brake pads and caliper from wheel. Clamp the free piston into the body of the caliper with mole grips but leaving space for the jammed piston to move. Pump the brake at the pedal/lever, the jammed piston may come free. Up to you if you push it right way out and spill fluid, or leave it sticking in a bit and hope to remove it completely later. 2/ If step 1 does not work to free the piston enough and you have split the caliper and are looking at a gummed in piston that is not moving. Don't grab it with mole/pipe grips as you will cuff the surface that the forms your brake seal. First tip is pretty messy but works sometimes.(Brake fluid is nasty stuff, be careful). You need a high pressure bike pump (180psi+) and an old inner tube. Cut the valve out the tube but leave some rubber round the base. Secure the caliper and pressurize the brake fluid/air by pushing the bike valve onto the caliper surface over the fluid feed hole (the one that passes fluid between the caliper halves). If you are working on the caliper side that has the connection to the master cylinder, block this up with an appropriately sized bolt. Might shift with the bike pump pressure. 3/ If the piston still refuses to move and you are on the point of chucking the caliper, the following worked for me: Fill the caliper completely with an appropriate fluid, I will suggest water here. Cover over the fluid feed hole with a small piece of inner tube rubber. Clamp the rubber to the caliper using a big vice and squeeze up as much as you dare to seal the fluid hole. Fun bit - get a blowtorch to the back of the caliper and boil the "fluid" inside. Pascal alone knows the pressure it will get to. The combination of heat, pressure and bad language managed to pop out the one I worked on. Might work for you too. ps. (Brake fluid is nasty stuff, be careful) Link to comment Share on other sites More sharing options...
Moderator mervin Posted May 20, 2011 Moderator Share Posted May 20, 2011 you can sometimes rig up a grease gun and pump the piston out with grease, Merv Link to comment Share on other sites More sharing options...
NEV Posted May 20, 2011 Share Posted May 20, 2011 [bit worried about the third option, as I understand brake fluid is very, very flammable, Link to comment Share on other sites More sharing options...
barkwindjammer Posted May 20, 2011 Share Posted May 20, 2011 The bike pump and a valve from an inner tube you'd have more success with a drinking straw from MacDonalds and a world championship piper Link to comment Share on other sites More sharing options...
wild foamy Posted May 20, 2011 Share Posted May 20, 2011 i second the grease gun and nipple(giggity) idea, basically screw a grease nipple into the appropriate hole (giggity) and pump away (giggity) be carefull if the nipple you are using isnt the correct thread pitch as this will damage your threads Link to comment Share on other sites More sharing options...
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