How to compress rear break piston with...

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  • How to compress rear break piston with...

    I was trying to replace rear pads as per Chris video. Everyone states no need for wheel removal. No issues with the take apart. Problem lies is that the middle piston isn't closed enough and it will only allow one brake pad on and not the other, even with moving it. Any Idea on how to safely compress piston. I don't seem to have enough leverage to do with hands. Tried the flat bar but again no leverage.
    appreciate all answers.

    also, if I have to lay bike down to remove wheel, then how the HECK, can I get to the brake on the other side? As you can see I'm new to self maintainence and would like some tips. Thanks in advance...

  • #2
    If you loosen the cap on the brake reservoir, or remove it altogether, then it will release the pressure from the brake fluid line. Be careful not to overflow the reservoir when you compress the pistons. Also, only do this if you are planning to do a fluid swap with fresh brake fluid. I cannot remember, but possible that the middle piston is controlled by the front (handlebar) reservoir. Even with the caps installed, you should still be able to compress them, but it takes more effort. Compressing pistons can be very slow process.
    Save $1000 a year in labor by doing your own maintenance!

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    • #3
      Barry, I "would" have helped you with I know the answer...but......once again you neglected to come to your Journeyman first, and ask me privately.

      Oh, Barry, what am I going to do with you?

      Do as Chris said.....remove the cap from the rear master cylinder, and place the cap back on...slightly at an angle, just in case some fluid tries to squirt upward. Then remove the cap from the front brake reservoir, and do the same.

      If you were all the rest of us, you could simply push the pistons back in by hand, or.........the real method is......with the OLD brake pads still in place, use a large flat blade screwdriver, or a smaller prybar, and place it in between the brake pads, and use leverage to pry the old brake pads apart.

      I have NEVER had a problem pushing the brake caliper pistons back into place.

      Now, if you are really good, which (you and I both know you are still learning here) would gently blow away any brake dust residue from the brakes and caliper.......then....gently spray the entire caliper down with Brake Clean. Then blow it all off again with compressed air, so that you are working with a cleaner caliper.

      Then remove the caliper from the disk....pry the OLD brake pads apart, pressing the caliper pistons back into place, then remove the OLD brake pads. Once the old pads are removed, make sure the brake pistons are fully depressed back into the caliper, then wipe down the rubber boots that keep bad stuff out of the piston seals.

      After using a anti-sieze or something similar on the contact points of the NEW brake pads, insert the new brake pads into the caliper, and...slide the "loaded" caliper back onto the disc, and bolt in place.

      Oh, and Barry, they are called BRAKES....not Breaks.

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      • #4
        Yes master, I have failed to bother you with my trivial ways of living, writing and riding. Yes, a college educated person should know brakes from breaks. Yet when working in a hospital with hip and other limb BREAKS, and you write that 500 x a day, you tend to get confused. The old brakes are back on. I removed the fluid as suggested. 2 of 3 Pistons go back down but not the furthest one which of course is little leverage for me to push with everything intact. I'm on the cusp. Sometimes I feel as if I am bothering you with stupid ****. I did the front breaks easy peasy, the video shows it popping in in 10 minutes for everyone else. Not for me. When I put old pads on yesterday, the wheel wouldn't spin, so pads even old ones weren't seated right in that clip. Today the piston still wouldn't go, but the old brakes were put back on and wheel spun freely. There is progress. Also, I DID use brake cleaner to get some junk out. I did not however use compressed air. Didn't think of that. Still in the minor leagues I suppose. Thanks for the write up and assistance. Maybe one day I'll get these things right.

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        • #5
          Barry, if 2 of the pistons did push back into the caliper, but 1 would might "possibly" be that the 1 piston is slightly cocked in the piston bore...the bore of the caliper. It doesn't take much for a piston to become slightly cocked in the bore. 99 times out of 100 this does not happen, is it is going to happen.

          If your last statement is correct...that you have the OLD pads in place, and the wheel spins have confirmed that you really do have a "need" to replace the rear brake pads....try it again...with the old pads in the caliper, and use a very large flat blade between the brake pads, and try to open that gap up between the pads by twisting the screwdriver, so that the flat blade acts as a lever to open the gap.

          This is a very rudimentary way of doing this. I guess since I have just about every tool a mechanic could ask for, I just reach into one of my tool boxes and find the spreading pliers, which are reverse of what normal pliers do.

          That 3rd piston should retreat into the caliper. It is also this try to get all three pistons to move smoothly the same action...and NOT one piston at a time.

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          • #6
            As shown in the illustration from the factory service manual, the front brake lever does not operate any of the rear caliper's pistons.

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            • #7
              Jim, thanks for posting that diagram. Makes it easier for all to understand.

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              • #8
                My pads at 16,000 miles: left front, right front, rear.

                If you want chatter-free and buttery-smooth brakes, lube your guideposts with Silglyde and clean the dust off your cylinders and coat with brake fluid before pressing them in for the new pads. You'll be amazed at the smoothness after doing these two things.

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                George - 2013 F6B Standard - Largo, FL

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                • #9
                  Thanks str8. I did most of that except lube the guideposts. Turns out it was NOT a piston, but one of the pad clips on the caliper was bent, and that stopped the pads. Had to lay the bike down, remove wheel and caliper. Used vise grips and viola, pads slid right in. I had a forum member swing by to assist, as I tried all the other things. But as what you and MMR and others, Chris etc suggested is to clean the Pistons, and surrounding areas. I learned a few things. How a 10 min brake job can take 2 days. But I also learned how to lay bike down safely, remove wheel and torque to spec, and remove caliper. While there, I cleaned it up. Thank you and everyone for your input. Special thanks to wingwing for his eyes, ears and knowledge on what my dilemma was.

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