Avid Code piston froze- Mtbr.com
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  1. #1
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    Avid Code piston froze

    Greetings fellow mountain bikers.

    Tonight I installed my first hydraulic brake; the Avid Code 203mm rear. I will change the front to a disc soon, but I started with the rear brake, as my funds would only allow it at the moment.

    I probably shouldn't have done this myself without previous experience, as I seem to have caused a big problem while trying to get the pads to quit rubbing.

    I installed the rear set, and they were rubbing from the start. I kept repositioning the caliper and re-tightening, in hope of getting the rubbing to stop. I couldn't find a sweet-spot where they wouldn't rub. In my frustration, I aligned the caliper, and squeezed on the lever while tightening the caliper to its mount. I had hoped it would align itself under pressure. Dumb move. When I let go of the lever, the lever would not return. The primary piston is stuck in. The wheel can still spin somewhat freely, so there is not any bound up pressure on the pads.

    What exactly is going on here?

    It seems there was air in the lines, and now they need to be reset and bled. Just a guess, as I'm not exactly sure why the piston would stick like this.

    Thanks for any help on this issue.
    Last edited by Marshall5; 05-25-2010 at 10:31 PM.

  2. #2
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    I pushed the pads outwards all the way, and the lever piston remains stuck all the way in and won't return.

    Should I have these bled, or is this a set which needs to be replaced immediately?

    As far as squeezing the lever in to get the piston stuck; I did have the disc between the pads just as it would be during riding, so it presumably would have done the same thing if I would have grabbed the lever hard during a ride.

  3. #3
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    Another update. As I move the loose lever back and forward, I notice the action is not very smooth at all. Something is dragging.

    I shined my light into the lever housing, and I can see the mouth of a C-clip which is catching and dragging on the inside of the lever body! This would be in addition to the main problem, meaning that even if the piston worked, the lever action would be hindered by this dragging C-clip.

    These brakes so far have proven to be engineered very poorly.

  4. #4
    nocturnal oblivion
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    Sounds like it wasn't user error. Take them back where you got them.

  5. #5
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    When I had first posted I was questioning my own install, but have since uncovered numerous problems with this brake by searching around through others experiences.

    And, to add fuel to the fire, the clearances designed in the brake are horrible.

    The position the caliper wants to naturally assume causes the inside of the caliper body--right near the rearmost frame bracket bolt--to rub on the rotor(!). A small 1mm more clearance would easily prevent this issue. Seeing as to how Avid could not avoid something as obvious as this, has me worried. A replacement Code is likely to be nearly as horrible as the first. Oh, boy.

  6. #6
    nocturnal oblivion
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    Post a pic, make sure you're not using the wrong mount adaptor, or that it's not backwards. Mounting issues can usually be fixed.

  7. #7
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    Quote Originally Posted by stumblemumble
    Post a pic, make sure you're not using the wrong mount adaptor, or that it's not backwards. Mounting issues can usually be fixed.
    Sure thing. Here are some photos. Notice in the second photo how the caliper body and washers are so close that they are touching the rotor. Also notice the gap on the right pad side between rotor and pad. I looked at the instructions as well as other bike photos to make sure I was mounting them correctly. However, something must be wrong here.

    The only apparent fix which I can envision would be to remove approximately 1mm of aluminum with my mill from the frame bracket left side, so that the rotor and bracket are bumped slightly to the left, adding clearance and centering the rotor between the pads. Would such a modification be appropriate?

    The bike shop said they would replace my brake set due to the condition of the lever and piston.





  8. #8
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    A possible fix is to have your shop face the frame tabs. This would potentially alleviate yourr rotor rubbing the back of the caliper and it will also give you a completely aligned surface to help with caliper adjustment. Just an idea.

  9. #9
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    Quote Originally Posted by cbratt
    A possible fix is to have your shop face the frame tabs. This would potentially alleviate yourr rotor rubbing the back of the caliper and it will also give you a completely aligned surface to help with caliper adjustment. Just an idea.
    Sounds good to me.

    I assumed these dimensions would be more standardized than they are from the beginning, so I suppose I should cut Avid some slack in the fitting department. My apologies.
    Last edited by Marshall5; 05-26-2010 at 01:21 PM.

  10. #10
    nocturnal oblivion
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    Don't touch your frame. I still think it's the adaptor. They make them thick and thin depending on the application. I have no idea why. But I do have thick and thin adaptors laying around from an old Hayes setup. Measure the adaptor width. My rear Avid adaptor is 11mm. Somebody who knows can chime in now...

  11. #11
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    Quote Originally Posted by stumblemumble
    Don't touch your frame. I still think it's the adaptor. They make them thick and thin depending on the application. I have no idea why. But I do have thick and thin adaptors laying around from an old Hayes setup. Measure the adaptor width. My rear Avid adaptor is 11mm. Somebody who knows can chime in now...
    Sorry about the delayed response.

    OK, I measured it. It is in fact an 11mm thickness. Do you know where I can order maybe a 9mm thickness black bracket for these brakes?

  12. #12
    nocturnal oblivion
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    It's not your hub though? Maybe the hub end caps were put on reversed shifting the hub over.

  13. #13
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    Quote Originally Posted by stumblemumble
    It's not your hub though? Maybe the hub end caps were put on reversed shifting the hub over.
    It's a 1-piece machined hub. Edit: Oh I got ya now, let me examine the right side to see if I can figure anything out. I'm not by the bike, but will drive to the shop soon to have a look.

    I called the local shop about facing off the frame tabs, and the guy talked to me like I was some moron.

    He also told me there is no thin mount for my Code brake.

    I don't get this. There's nothing which can be assembled wrong. This is just "the way it is".

    Apparently some hub makers decide to do what they please and make them a couple mm wider than the norm. They are Vuelta Zero-Lite wheels that I just bought.

    Just curious, why would only some brakes have thin and thick mounts available if this can happen on any bike?

  14. #14
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    Everything is fine with the hub. It's exactly 135mm; I measured with the caliper.

    I talked to another guy who has worked with many frames, and he told me what cbratt said above about the tab facing. He said that since the bike didn't come with discs as OEM, the company may not have faced the tabs during its production. He said just to take my caliper, measure the tab thickness, then remove the same amount from each with a file. I am going to knock off about 0.5mm, which will be about what is needed to completely stop the caliper from rubbing.

  15. #15
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    Huh. Let us know if it works, may be just a matter of filing away the powdercoat. Good work on investigating the options first.

  16. #16
    sm4
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    put a washer into it, to wider the frame, this will help the caliper central at the disc.
    Attached Thumbnails Attached Thumbnails Avid Code piston froze-avid-code-1.jpg  


  17. #17
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    Quote Originally Posted by sm4
    put a washer into it, to wider the frame, this will help the caliper central at the disc.
    That's actually a good idea. Last night, I stood over the frame, and put a flat blade of metal up against the frame tabs before I started filing. I noticed that the frame tabs are not parallel with the hub surface. The blade was angled towards the wheel by a few degrees. So, the further something extends rearward off the tabs, the closer it will get to the disc, which is why the rear of the caliper is rubbing.

    The washer will widen the frame and correct that angle so that the tabs are close to parallel with the disc plane.

  18. #18
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    Quote Originally Posted by Marshall5
    That's actually a good idea. Last night, I stood over the frame, and put a flat blade of metal up against the frame tabs before I started filing. I noticed that the frame tabs are not parallel with the hub surface. The blade was angled towards the wheel by a few degrees. So, the further something extends rearward off the tabs, the closer it will get to the disc, which is why the rear of the caliper is rubbing.

    The washer will widen the frame and correct that angle so that the tabs are close to parallel with the disc plane.
    Wow, some crazy advice on here...

    The problem is not the frame, not the adapter. and not the hub. You got some lazy pistons in your caliper or some not working properly. Your disc should be centered in the caliper opening, your current setup is way off.

    1. Check if all piston are moving.
    2. Push every piston all the way in.
    3. Put the caliper back on the adapter and leave it loose.
    4. Pull the lever a few times, hold the lever.
    5. Tighten the caliper screws and check to be sure the caliper is not moving while tightening.
    6. Check if the rotor is centered in the caliper opening.

    *7. If still not working properly, bleed the brakes and lube the pistons and start again.

  19. #19
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    Quote Originally Posted by Megaclocker
    Wow, some crazy advice on here...
    ........................
    If you look again at the caliper and frame, you can the the rotor being too far left of center. Center being the seam of the caliper.

  20. #20
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    Megaclocker,

    The frame tabs were not faced properly from the factory. The caliper mount itself was rubbing the rotor, and surely too close. This mount is independent of the piston action of course. The only fix was getting it away from the rotor.

    The washer idea was a ghetto fix, the more I though about it, and I definitely didn't want to do that.

    I since filed the frame tabs parallel to the hub. I removed about ~1mm total.

    The new brake arrived today. It is now mounted, and the caliper is centered perfectly over the rotor, and the brakes work great now.

    So, there were two problems at the start. The first brake I received had a bad bleed or piston issue, and the other problem was that the frame tabs protruded too far.

    Both problems have been solved.

    Thank you guys for the input!

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