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  1. #1
    Member BoroughRider's Avatar
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    Hydraulic disc brake problem. Suggestions?

    I recently got some grimeca hydaulic disc brakes. I got someone to bleed them for me and before installing them, I somehow squeezed the lever and now the piston seems to be permanently closed or seized so that when i insert the rotor, the pads constantly rub against the rotor. I'm not sure what to do. I went to my LBS and told me I needed to rebleed the line. I'm a little skeptical about the mechanic's knowledge about disc brakes because he doesnt service them so before jumping out to do something, can anyone offer some advice? Any help would be really appreciated!

    Thanks

  2. #2
    Senior Member mtbikerinpa's Avatar
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    I am not certain about Grimeca's system, but in most open-system Hydraulic units when you do that it is simple. Take a thin but wide bladed flat screwdriver and gently pry them open. The volume of fluid will merely force back into the reservoir.
    On a closed-sysem it is a little more complex. If a gentle force as in the former will not work, place a light pressure on the pads as described and open the lower bleeder ever so slightly. Only enough to relieve the line. Close the bleeder immediately, as you do not want anything getting sucked back in.
    That should do it. Unfortunately a very common mistake, intentional or not. No big.
    Aviation Mechanic, Bike racer, Fitness Equipment Restorer

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  3. #3
    The Rabbi seely's Avatar
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    If its Hayes, we have had this same problem with several pairs of new HFX9 brakes on new bikes recently. We just send them back in to Hayes for warranty. Its almost like the piston is sticking and doesnt full retract.
    commuter turned bike mechanic turned commuter (also a Velocity USA employee, but this is my personal account)

  4. #4
    I drink your MILKSHAKE Raiyn's Avatar
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    Quote Originally Posted by BoroughRider
    I recently got some grimeca hydaulic disc brakes.
    Quote Originally Posted by seely
    If its Hayes
    Err no. Not Hayes.

  5. #5
    The Rabbi seely's Avatar
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    Quote Originally Posted by Raiyn
    Err no. Not Hayes.
    Hey, its finals week and my brain is melting as we speak. I can't ALWAYS be right!
    commuter turned bike mechanic turned commuter (also a Velocity USA employee, but this is my personal account)

  6. #6
    Member BoroughRider's Avatar
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    Quote Originally Posted by mtbikerinpa
    I am not certain about Grimeca's system, but in most open-system Hydraulic units when you do that it is simple. Take a thin but wide bladed flat screwdriver and gently pry them open. The volume of fluid will merely force back into the reservoir.
    On a closed-sysem it is a little more complex. If a gentle force as in the former will not work, place a light pressure on the pads as described and open the lower bleeder ever so slightly. Only enough to relieve the line. Close the bleeder immediately, as you do not want anything getting sucked back in.
    That should do it. Unfortunately a very common mistake, intentional or not. No big.
    Thanks for the advice, mtbikerinpa. But, unfortunately, it still doesnt want to pry open. I'm pretty sure its an open system however, I still cant seem to get it to seperate. Any ideas on what I should do next? I looked up the manufacturer's manual. All I could find was this:

    http://www.grimeca.it/eng/pdf/1.pdf

    I have the system 1. It doesnt do a good job of explaining much. It suggests "opening the tank to remove excess brake fluid" (dont know how) to get the brake pads open.

  7. #7
    I drink your MILKSHAKE Raiyn's Avatar
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    Quote Originally Posted by seely
    Hey, its finals week and my brain is melting as we speak. I can't ALWAYS be right!
    Even skimming you should have spotted that in the first sentence

  8. #8
    Giggity giggity! Dirtbike's Avatar
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    When hayes pistons are stuck, it is usually because they are crooked, or they need some fluid on the seals.
    Rides: 06 Demo8 II, Yeti DJ
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  9. #9
    d_D
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    You might just not be pushing the pad back hard enough.
    Be careful as it is possible to damage the pad if you use too much force. It's better to remove the pads first or use something like a plastic tyre leaver which is softer and has more surface area.

    In most open systems the seals pull the piston back when you let go of the lever so the seals need to be quite tight. It takes more force than you would think to actually move the piston.

  10. #10
    Member BoroughRider's Avatar
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    I fixed the piston problem... but now I really need to rebleed. the lever feels squishy now. but... then again, ive lost a lot of patience so im just gonna ride with it sicne it still works. Thanks guys

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