It was one of those things where you think your clear until it gets yah. It clipped the tip of my finger, so I was almost clear and yes I did read the warning but hey, sometimes you just have one of those days. I could'nt been clear across the room and it still would got me, shot my eye out or something.crazybrit wrote:Did you read the service manual before you blew them out? There is a huge warning about keeping your fingers out of the way.jafo wrote:Caution!!!!!! When working on calipers like these, be very very careful. It requires compressed air to get the pistons out of the caliper. Believe me when I say, they come out like bullets. So be careful and don't have your fingers in the way like I did. I had a heck of a blood blister when one shot out and pinched my finger. Thats why I say to try spinning the front rim first before going through all that trouble. Also try using a wash towel or some king of thin padding to protect the pistons from being chipped when they hit the outside part of the caliper. They are so tight in the seals that they build up pressure behind them before popping out.scheckaet wrote: Interesting Jafo. Could be that too, I recently replaced the brakes... I will tear them down tonight and see what they look like.
Easiest thing is to just push the pistons out using the brake lever. In my case one wouldn't budge so I had to use compressed air.It took over 40psi to force it out. This will crush your finger. Use a piece of plywood to soften the impact of the piston coming out, you need to use something (other than your finger) as you don't want it hitting the other side of the caliper.
Like I said 5 posts ago, mine are mushy and I think it is caused by one of the pistons binding. I've removed it, the seals look ok but it still happens. I was thinking of removing it again and gently smoothing it using some 800 or 1000 grit wet paper.
My wheel didn't have resistance when spinning it, the pad wasn't dragging, rather one of the pistons would just advance upon pressing the lever and then about 80% thru the lever stroke, it would pop back into the caliper body. The other piston was fine so I had poor braking power, uneven pad wear and mushy feel. Maybe the mushy feel is due to a problem elsewhere (master cylinder), dunno. Fix one thing at a time is always my view, so I figured both pistons should advance smoothy and until they do, I won't look elsewhere.
tony
The pistons are not suppose to retract back into the caliper very much. They should keep a small amount of pressure on the rotor until you apply more pressure to them through the mastercylinder. It's kind of like holding a piece of paper with your fingertips and apply pressure and letting off without dropping the paper. Thats the best I can describe it. I'd start with the master cylinder and go from there if it were me. At least thats what I've done. as far as using abrsive paper, I personaly don't think it'll work but if the pistons are bad anyways what the heck. It's just time your spending. The reason I did'nt try the sandpaper was because to get all the bad area out of my pistons, I would have to take off a good amount of material and would have wound up making the piston out of round or no longer fit the caliper. Plus I don't like to band aid something like brakes especialy on an off-road bike. I'd rather spend the extra cash and put in new parts so I won't have to tear it down sooner than later, or wind up in the hospital from brake failure. Your call though, thats just my take on it. I'm sure it's stuff you've already thought through anyways.
As far as the piston popping back into the caliper, that wierd. I would say that might cause a mushy feel in the brake. Mainly because if the one psiton is popping back into the caliper, it has to be letting off some pressure I would think. I've never seen a caliper piston do what your talking about. Is there fluid leaking out around that piston?