Results 1 to 8 of 8
  1. #1
    mtbr member
    Reputation:
    Join Date
    Oct 2011
    Posts
    9

    how to adjust tektro draco pistons?

    I recently bought a bike with these hydrolic disk brakes and it seems that the piston on one side is doing almost all of the movement. Is this normal, or is there a way to balance out the piston movement to where its symmetrical?

  2. #2
    mtbr member
    Reputation: Shalom's Avatar
    Join Date
    Nov 2008
    Posts
    1,998
    Are the brakes new? If not, it could be that the seals are shot and need replacing. It could also be that the piston has been pushed in on an angle and has jammed. Alternatively, it could be that the caliper is not centered on the rotor, meaning that one piston has to move a lot more to contact the rotor than the other piston.

    Sorry for all the information, but without more information from you, it is a touch hard to diagnose.

    Good luck.

  3. #3
    mtbr member
    Reputation:
    Join Date
    Oct 2011
    Posts
    9
    Thanks for the reply! The brakes are on a 2010 rockhopper, so they're not new. I have the caliper off the rotor entirely, so it shouldn't have anything to do with that.

    When I squeeze the brake handle, one piston comes out a ways and moves out even further after each consecutive squeeze. The other piston moves VERY slightly, but when i release the handle it goes back in to where is was initially in the fully retracted position.

    It doesn't look to be at an angle, and if it were jammed I'm guessing it wouldn't even budge at all? Do you think it would be bad seals then, or something else?

  4. #4
    mtbr member
    Reputation: Shalom's Avatar
    Join Date
    Nov 2008
    Posts
    1,998
    Based on your description, it sounds like one piston is behaving as it should, whereas the other is experiencing some level of vacuum, pulling it back in. Could be seals. Or needing a bleed? If there is air in the caliper, weird things could be happening. Hopefully someone who has a better idea comes along soon.

    If it were me, I would bleed the system fully. If that doesn't work, try a seal replacement. Or take it in to your LBS to get it checked.

  5. #5
    mtbr member
    Reputation:
    Join Date
    Oct 2006
    Posts
    2,621
    This behavior is typically the result of a "sticky piston". The piston needs "exercised" and cleaned.

    Remove the brake pads. Press the free piston all the way back into the caliper body. Hold back the free piston while you pull the lever to cause the sticky piston to extend. Be careful not to push the piston all the way out. Use a Q-tip dipped in the appropriate brake fluid (in this case, I believe it is mineral oil) to clean the exposed surface of the piston. Press the sticky piston all the way back into the caliper body. Run the piston in and out a few times until it operates normally. End up by pressing both pistons all the way back into the caliper body, install the pads and with the caliper mounted on the bike and the wheel installed, pull the lever a few times to reset the pads/pistons out to the normal position.

    Due to the leverage required to hold back a piston (or pressing one back into the caliper), I find this easiest to do with the caliper mounted on the bike and the wheel removed.

    If this doesn't work, I would bleed the brake to make sure there wasn't air behind the sticky piston.

  6. #6
    Jamin, Applesause, No?
    Reputation: Senor StrongBad's Avatar
    Join Date
    May 2009
    Posts
    708
    Quote Originally Posted by gmcttr View Post
    This behavior is typically the result of a "sticky piston". The piston needs "exercised" and cleaned.

    Remove the brake pads. Press the free piston all the way back into the caliper body. Hold back the free piston while you pull the lever to cause the sticky piston to extend. Be careful not to push the piston all the way out. Use a Q-tip dipped in the appropriate brake fluid (in this case, I believe it is mineral oil) to clean the exposed surface of the piston. Press the sticky piston all the way back into the caliper body. Run the piston in and out a few times until it operates normally. End up by pressing both pistons all the way back into the caliper body, install the pads and with the caliper mounted on the bike and the wheel installed, pull the lever a few times to reset the pads/pistons out to the normal position.

    Due to the leverage required to hold back a piston (or pressing one back into the caliper), I find this easiest to do with the caliper mounted on the bike and the wheel removed.

    If this doesn't work, I would bleed the brake to make sure there wasn't air behind the sticky piston.

    Agreed: this has fixed all my sticky piston problems so far!

  7. #7
    mtbr member
    Reputation:
    Join Date
    Aug 2012
    Posts
    1
    Quote Originally Posted by gmcttr View Post
    This behavior is typically the result of a "sticky piston". The piston needs "exercised" and cleaned.

    Remove the brake pads. Press the free piston all the way back into the caliper body. Hold back the free piston while you pull the lever to cause the sticky piston to extend. Be careful not to push the piston all the way out. Use a Q-tip dipped in the appropriate brake fluid (in this case, I believe it is mineral oil) to clean the exposed surface of the piston. Press the sticky piston all the way back into the caliper body. Run the piston in and out a few times until it operates normally. End up by pressing both pistons all the way back into the caliper body, install the pads and with the caliper mounted on the bike and the wheel installed, pull the lever a few times to reset the pads/pistons out to the normal position.

    Due to the leverage required to hold back a piston (or pressing one back into the caliper), I find this easiest to do with the caliper mounted on the bike and the wheel removed.

    If this doesn't work, I would bleed the brake to make sure there wasn't air behind the sticky piston.

    I just popped the piston out of my brake caliper after having this same problem. I've got the piston back on the front to keep crud out for now, riding brakeless in the front.


    I suppose I just need to get the right fluid and refill properly. I have Tektro Draco Pro brakes, on a GT.

    Any help is appreciated.

  8. #8
    mtbr member
    Reputation:
    Join Date
    Oct 2009
    Posts
    898
    I found one piston in my rear brake was sticking causing a spongy feel at the lever. I did the oil-on-piston trick above and it worked!

    I held the moving piston back with a pedal spanner and pulled the lever. The stuck piston moved and then I wiped around it with a qtip coated in oil. I cycled it a few times and it now feels much better at the lever.

    I've also found that the brake noise I was experiencing has gone. I wonder if the unequal pad pressure has been since new. I'll try it on my front brake next.

Similar Threads

  1. Replies: 12
    Last Post: 08-10-2013, 06:42 AM
  2. Replies: 2
    Last Post: 01-20-2012, 12:24 PM
  3. What brake pads work with Tektro Draco SL calipers?
    By JacksonCampbell in forum Brake Time
    Replies: 0
    Last Post: 05-15-2011, 04:29 PM
  4. What does sag adjust and rebound adjust do
    By firstlast in forum Beginner's Corner
    Replies: 11
    Last Post: 03-04-2009, 07:31 AM
  5. Goldtec Draco Hubs
    By mtnbykr06 in forum Downhill - Freeride
    Replies: 0
    Last Post: 12-10-2006, 05:50 PM

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •