Mechanical discs not being reliable- Mtbr.com
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  1. #1
    Hmm..doughnuts
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    Mechanical discs not being reliable

    I own a set of BB5 mech disc brakes on my Hardrock (pictured on left) and they really have been giving me some issues. Nothing serious, just frusterating. They have a bad tendency to get out of allignment causing that annoying "zing" noise. The front fork has some flex in it and as a result the rotor will hit the pads when lateral pressure is placed on the front wheel. Somehow this causes the disc to actually bend by 1-6mm and stay bent like that unless I pull it back into place by hand. If I do not adjust this on a regular basis I am forced to loosen my brakes up to the point where braking is horrible. This also happens whenever I take off the front QR and place it back on, even with same tension.

    Also, they also sqeak really bad but they didn't when I first got them. I cleaned off the pads and rotors and they still sqeak. I just got some new organic pads. Maybe they will help.

    Anyone else have this problem/s? I didn't think discs were supposed to bend as easily as mine are.
    Need to find a cheap Marzocchi DJ3 fork cheap

  2. #2
    ballbuster
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    Sloppy or flexy hub?

    Check to be sure your bearings aren't loose. I had similar issues with flex and my BB7s with Shimano XT hubs. The problem went away when I switched to Hope hubs for some reason.

  3. #3
    Meh.
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    Bring it to a shop. It sounds like when you're "adjusting" it, you're actually doing harm. I don't mean to be critical, but I really don't think you know what you're doing.

    As for the QR, how do you know your tightening it to the exact torque that it was at before?

  4. #4
    Hmm..doughnuts
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    Well, if the discs are physically being bent in a given direction, how else can they be fixed besides bending them back into place? If there is a better way of fixing this problem I am all open to suggestions.

    In regards to the torque on the QR, I spoke incorrectly and gave the wrong impression. what I meant was I untightened it, counted the number of turns on it, removed it, and place it back on with the same number of turns. I know this isn't exact, but the difference in pressure couldn't be so great that the disk is offset every time, could it? If so how can anyone expect to use a QR with disks without readjusting them everytime the front wheel is taken off.

    (I have to fit my bike in a car to transport it and I don't have a rack so I have to take the wheel off whenever I go to my friend's house (40 miles away) or any good riding trails (none close by).



    I think pimpbot might be right about the hubs. My friends and I tried to fix them one day but we didn't manage to get anywhere. They are so tight we couldn't open them to see if the bearings had any problems. I'll probably take them to a LBS to get them worked on.
    Need to find a cheap Marzocchi DJ3 fork cheap

  5. #5
    mtbr member
    Reputation: mrpercussive's Avatar
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    Quote Originally Posted by trail trekker
    Well, if the discs are physically being bent in a given direction, how else can they be fixed besides bending them back into place? If there is a better way of fixing this problem I am all open to suggestions.

    In regards to the torque on the QR, I spoke incorrectly and gave the wrong impression. what I meant was I untightened it, counted the number of turns on it, removed it, and place it back on with the same number of turns. I know this isn't exact, but the difference in pressure couldn't be so great that the disk is offset every time, could it? If so how can anyone expect to use a QR with disks without readjusting them everytime the front wheel is taken off.

    (I have to fit my bike in a car to transport it and I don't have a rack so I have to take the wheel off whenever I go to my friend's house (40 miles away) or any good riding trails (none close by).

    I think pimpbot might be right about the hubs. My friends and I tried to fix them one day but we didn't manage to get anywhere. They are so tight we couldn't open them to see if the bearings had any problems. I'll probably take them to a LBS to get them worked on.
    maybe it could be the alligntment of the calipers which went out instead of the rotors being out of true???

  6. #6
    Hmm..doughnuts
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    When the bike is standing still the calipers are alligned perfectly, but when it's moving that may be a different story.

    The calipers may be causing the disc to get bent when the fork flexes, but the only thing I could do about that is get a nicer fork. I do not want to spend that much money at this time. Thanks for the suggestion though.
    Need to find a cheap Marzocchi DJ3 fork cheap

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