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  1. #1
    never ender
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    Long-term sticky piston fix?

    Anybody know of a way to keep the pistons on my Shimano hydros running smooth for longer than 2 months? I think I'm running into the same problem that lots of other folks have mentioned with Shimano brakes, but I haven't found any solutions beyond cleaning and lubing. My usual cleaning regimen is to extend the pistons, clean with a dry rag, then lube with silicone, pumping the pistons in and out a bit. I wait a while, then push the pistons back in and clean everything with a little bit of paint thinner on a rag wrapped around a knife blade. When I was using metallic pads I was doing this once every couple weeks. Now that I'm running resin pads it's a little bit less of a problem, and I only have to do clean and lube the pistons once every month or two, but it bugs me. If I didn't have to mess with my brakes in between pad changes I'd be pretty stoked.

  2. #2
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    Why do you think the pistons are sticking? Do they not self-adjust? Do they rub?

    During normal operation the pistons don't slide on the seals. The seals flex out when the brakes are applied and then they flex back to retract the pads a little. When the brakes wear sufficiently the seal will slip on the piston, thereby self adjusting. However in practice this self adjusting doesn't work perfectly.

  3. #3
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    Hey, weren't you at the Bikeskills clinic a while back? How goes, man?

    From what I've read here, sticky pistons are a common problem with Shimano hydros. I suppose it has to do with pad dust and dirt packing up around the lip of the seal. When I moved back to California from Hawaii I was running metallic pads, and the pistons were sticking REALLY bad. Switching to resin pads helped, but I still have to clean and lube them once in a while. Cleaning and spraying with silicone will usually keep them running fine for two or three months, so it's not that big a deal...I just get envious of people who say they only mess with their brakes once or twice a year.

  4. #4
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    I've been running XTRs a couple years now and at first had frequent sticking problems, with the need to clean and lube the pistons every two or three rides. For the last half year or so they haven't needed it at all, maybe they just needed to bed in or something. I used mineral oil rather than silicone for lubing the pistons, as you describe.

    I don't know if its possible, but can you give the sticky piston a quarter turn spin in its bore to see if it sticks less in a different orientation? Obviously, avoid pulling it out or scratching the surface.

  5. #5
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    Oh yah, that was me! I remember you. You should come on up some time and we'll go for a ride at Annadel.

    So do the brakes drag when the pistons stick?

    Also I don't know what material the seals are made of but you might want to use mineral oil to lube them. If the seals are made of silicone and you lube them with silicone then they can swell up (yes, it's weird), causing even more sticking I'd imagine.

  6. #6
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    Man, I haven't been up to Annadel in weeks. I'm working all the time these days. I could maybe meet you halfway at Tamarancho...I've been going over there and doing a 2-loop ride every week or so. PM me if you want and we can figure something out.

    As to the brakes, the sticking doesn't directly cause the brakes to drag, but it sometimes causes one of the pistons to stay partially retracted, and then the other one doesn't retract enough. No problems so far lubing with silicone spray...I've done it twice in the past few months and it actually seems to work better than Shimano mineral oil. Or they could have just broken in all the way, like shinewheel says. Time will tell, I suppose.

  7. #7
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    Tamarancho is an option, I'll have to see when I can get some time to head down there.

    Hmm maybe you could lightly sand the pistons with some 1500 grit sandpaper? There might be machining marks in them causing them to hang up a bit. Don't sand too much or you could go through the anodize.

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