March 8, 201511 yr I'm trying to install new rear brake pads on my 2010 EVO 250, but can't push the piston back into the calliper to make room for the new pads. I removed the master cylinder cap and loosened the bleeding nipple but still no joy. Any suggestions on what to try next ?
March 8, 201511 yr If pistons are moving out ok with old pads, I would take out the actuating rod from master cylinder end and try again. You may have over adjusted and it blocks backflow of brake fluid. wouldn't open bleed nipple in case you get air in as they can be a pig to bleed.
March 9, 201511 yr Author That wasn't the problem as fluid flowed freely in both directions. I then disconnected the caliper from the hose and still couldn't get the piston to push back in. I'm now trying to get the piston out to check why it's stuck. What's the best method to get the piston out of the caliper ?
March 10, 201511 yr Author It turns out the pistons have a lip in the inside for a slide hammer to grab and pull them out. I got the pistons out and there was nothing in the inside that would prevent them from going back in. I did notice however that they were not being pushed in straight. I believe this was the cause of the problem as the pistons got wedged, probably when I tried to pry open the old pads with a screwdriver. So the next time I'll be very gentle pushing the pistons back in so that they go in straight and don't get wedged. I'm yet to test the brakes on a ride, but they seem fine in the garage.
March 10, 201511 yr The pistons can get a bit twisted in their bores once they have extended a bit too far out (when the pads have worn right down) and tend to jam in there. Once they are that far out, there's just not enough piston left in the caliper to keep them straight. The four pot calipers are the worst for this, I've lost count of the times I messed around with them because of this (I'm too tight and want my money's worth out of the pads!), but it can happen with any caliper. Just don't let the pads wear too low next time. A neat trick to bleed out the hydraulics is to use a short pipe that fits the nipple and a large syringe, then gently back bleed from the nipple.
May 10, 201610 yr I'm trying to install new rear brake pads on my 2010 EVO 250, but can't push the piston back into the calliper to make room for the new pads. I removed the master cylinder cap and loosened the bleeding nipple but still no joy. Any suggestions on what to try next ? I've installed my new rear brake pads last night and came accros the same problems , in the end It was the piston that was jammed so insure you press evenly , and yes I had to re bleed , due to access
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