disc brake piston

ol55 · Commuter Joined: Feb 09, 2009 Posts: 391 Location: VA

What is the best way to get the piston out?

redstedman · Posted: Sun Feb 07, 2010 9:36 am Post subject:

Air pressure. Put a piece of board(1/2"to 3/4"thick) in front of the piston and wear eye protection and keep your fingers out of the way. When it comes out it will be moving fast. If the piston is REALLY stuck you might have to use the bikes hydrolics to push it out.(kinda late for that now that its off) Take the caliper off the disc, USE THE BOARD, and push it out with the peddle/lever. Or, find one used for cheap. Not a siezed up one. Be careful

05c50 · Posted: Sun Feb 07, 2010 10:48 am Post subject:

Bolt the caliper back together (so the piston doesn't go flying) and apply air pressure to the hole where the line attaches. If that doesn't work, find a grease fitting to thread into the hole and use a grease gun to pump it out.

..............Paul

jvandyke · Posted: Sun Feb 07, 2010 2:47 pm Post subject:

I left it on the bike, used the brake lever to push it out. I rebuilt my caliper last week, never took it off the bike (unbolted it but left the line attached). Be sure to grease the piston and basically everything else except the pad to disc contact points, keep those clean!

jeepurz · Posted: Sun Feb 07, 2010 5:31 pm Post subject:

05c50 · Posted: Sun Feb 07, 2010 5:38 pm Post subject:

The rubber parts in a brake system can be damaged if "grease" is used when assembling them. It's best to use brake fluid during assembly unless you have 100% silicone grease. Regular grease can make the rubber swell. I know, I've done it. I learned my lesson. Embarassed

.................Paul

ol55 · Commuter Joined: Feb 09, 2009 Posts: 391 Location: VA

Thanks for the sugesstions. Tried 80 psi using my pancake compressor with a little connection leakage but no go. I used an air chuck tube that screwed in. I thought it would fall out because the last time I rode the brake would not release. The master is off for rebuild also that method won't work until I rebuild the MC. What is the system psi on a 350?

Since I am using new pads, ok to use PB blaster on this?

Larry

05c50 · Posted: Sun Feb 07, 2010 9:44 pm Post subject:

The difference between using air and grease, is that air will compress and grease won't. An average grease gun will supply more then enough pressure to push the piston out. The only things that might be affected by using PB blaster will be the the seal and dust boot, but I suppose you're going to replace them anyway.

...........Paul

jvandyke · Posted: Mon Feb 08, 2010 6:28 am Post subject:

jeepurz · Posted: Mon Feb 08, 2010 12:38 pm Post subject:

bamos3 · Posted: Mon Feb 08, 2010 5:34 pm Post subject: Piston removal

Had problems with my Yamaha brake piston, used air pressure of 120 psi. Piston only moved 1/16th of an inch and no more. I pushed it back in and kept repeating cycles of pressure and pushing until eventually it popped.

ol55 · Commuter Joined: Feb 09, 2009 Posts: 391 Location: VA

Thanks for the tips. Used liquid wrench and increased the pressure to 110 and it came right out. The old pad was rusty but the piston and the cylinder look good. Do the backs of the pads get grease or adhesive?

Larry

05c50 · Posted: Tue Feb 09, 2010 6:50 am Post subject:

Clean everything up real good. Make sure the groove that the ring seats in is completely clean, put some silicone grease on the back of the pad and you should be good to go. Don't use silicone (rtv) like the po of one of my bikes! The pad was glued to the piston and the piston was glued to the cylinder. Mad

............Paul

ol55 · Commuter Joined: Feb 09, 2009 Posts: 391 Location: VA

The bleeder valve is stuck also. Any suggestions for removing it before I break it off?

05c50 · Posted: Wed Feb 10, 2010 6:13 pm Post subject:

Heat the caliper with a small torch. The aluminum caliper will expand and the bleeder will screw out.

.........Paul