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TRP HY/RD Pistons not moving

mickisupmickisup Posts: 295
edited January 2016 in MTB workshop & tech
The pistons on my TRP Hydraulic brakes are not moving when brake lever engaged, would/should this be resolved by bleeding the brakes?

They are self adjusting but I can't see any way of getting at the pistons so am assuming a full bleed is the only way to fix.

Many thanks

Posts

  • The RookieThe Rookie Posts: 27,747
    If they went from working to not working, then you probably have a leak, bleeding (refilling in this case) will work until it enough has leaked again.....
  • mickisupmickisup Posts: 295
    Thanks, yes I am suspecting a leak but no idea where it comes from, something may have perished? Just wonder whether that can be replaced or whether the calipers have had it.
  • oodboooodboo Posts: 2,177
    I take it the cable is pulling the actuator ok?
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  • Cable?
  • oodboooodboo Posts: 2,177
    Yes, they're a cable actuated hydraulic brake, I have them on my cx bike.
    I love horses, best of all the animals. I love horses, they're my friends.

    Strava
  • lpretro1lpretro1 Posts: 237
    Is there pressure at the lever? If there is and the pistons are simply not moving then bleeding will do no good as that is just to remove air - the caliper needs dismantling and new piston seals fitting. If no pressure at the lever then it is a different problem
  • oodboooodboo Posts: 2,177
    Ignore the levers for now, if you push the actuator on the caliper does it work from there? If yes then is the brake cable, if not the look for a manual to see how to strip or bleed them.
    I love horses, best of all the animals. I love horses, they're my friends.

    Strava
  • mickisupmickisup Posts: 295
    When you say actuator you mean where the cable anchors?

    The brake lever has pressure and moves the cable and I think what you refer to as the actuator however the pistons don't move.

    They did yesterday but I needed to push the pistons back inwards to fit new pads and they were too far extended.

    I opened the bleed nipple a little to moved the pistons back and since then the pistons are back inward of the the caliper and don't move out.
  • The RookieThe Rookie Posts: 27,747
    So you deliberately dumped some fluid and didn't think to tell us?

    There should have been no need to lose fluid, but now you have it will need to be put back or guess what? The brakes won't work!

    In future it's better to find out how to do things before you make a mess of them and not after!
  • cooldadcooldad Posts: 32,904
    Probably should have mentioned that in the first post, and probably shouldn't have opened the bleed nipple to fit pads.

    No idea about those brakes specifically, but I'd say after doing that it's likely you got air in or fluid out.

    Edit - I shouldn't open loads of threads and post an hour later.
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  • mickisupmickisup Posts: 295
    Apologies for lack of clarity. The reason for letting fluid out is that as the pads bear the pistons self adjust, so when the pads are shot and replaced the new pads will fit but the rotor won't fit between....

    Letting some oil out allows the pistons to be fully pushed back into the caliper, its not possible to do this otherwise as they both won't reset correctly and the pads just rub.

    However once a small amount of oil is released the pistons can be reset but then the stop working when the brake is engaged, its a flawed design IMHO or I have some other underlying issue.
  • oodboooodboo Posts: 2,177
    Don't you just push the old pads apart with a screwdriver or something before replacing them? That's what I've always done anyway.
    I love horses, best of all the animals. I love horses, they're my friends.

    Strava
  • mickisupmickisup Posts: 295
    Tried doing that with a tyre lever and when one is pushed the other just compensates, tried pushing both and it doesn't work. Releasing a little fluid allows reset but results in no movement at all.

    If the pads were not quite as thick it would be feasible but significant rubbing is unavoidable.

    I have a bleed kit coming this morning so will see if that fixes.
  • cooldadcooldad Posts: 32,904
    That doesn't make sense. If you fit new pads, and the brakes compensate as they wear, the fluid level will be the same when you fit new pads.
    I don't do smileys.

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  • meanredspidermeanredspider Posts: 12,550
    Yes - it doesn't make sense that you had to let fluid out - you would, however, need to have the lever in the fully returned position to let the fluid return to the reservoir. Anyway, now it seems as though you'll need to top the fluid (whichever sort it is) up by removing the reservoir cover.
    ROAD < Scott Foil HMX Di2, Volagi Liscio Di2, Jamis Renegade Elite Di2, Cube Reaction Race > ROUGH
  • mrdsgsmrdsgs Posts: 331
    edited January 2016
    you are getting something wrong. I have regularly changed pads on trp hy/rd and never had to bleed etc.

    the pads do not hold the pistons in. if you remove the pads the pistons do not close together.

    remove wheel, remove old pads, fit new pads, replace wheel. job done. 5 mins per wheel max.
    Colnago Addict!
  • The RookieThe Rookie Posts: 27,747
    Unless the cable pull is botched so the master cylinder can't empty back into the reservoir, with this bike anything now has to be considered possible or even perhaps likely.
  • meanredspidermeanredspider Posts: 12,550
    It's mineral oil used so reasonably easy to sort but it's really important that the lever can fully return on HyRds - that's why there's the setting pin too.
    ROAD < Scott Foil HMX Di2, Volagi Liscio Di2, Jamis Renegade Elite Di2, Cube Reaction Race > ROUGH
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