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  1. #1
    all about the rhythm
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    Help Removing an Eccentric BB

    The bottom bracket I am trying to take out is on a Trek Tandem. It appears to be the same BB found on Trek's Soho model bicycle.

    The bottom bracket looks like this....

    I have removed the bottom bracket spindel and bearing case. The only thing left in the frame is the eccentric BB shell. I loosened/removed the main bolt but now I don't know what to do. I tried to hammer it out with a rubber mallet without success. The drive side of the shell has two hex head indentations but they don't seem to do anything. can anyone help me out with this problem?

    Thanks in advace....

  2. #2
    The Red Lantern Rev.Chuck's Avatar
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    I believe that one is in two halfs. after you remove the bolt you need to stick a punch through the BB hole and tap the first half out and then you should be able to get to the other side easy.
    The hex holes are for allen wrenches so you can adjust your chain tension by rotating the eccentric. For that matter, they might rotate right out if you stick and allen in it and just turn it.
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  3. #3
    Senior Member
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    The eccentric is in two parts, wedging like a quill stem. You can insert the bolt again, leaving it a couple of turns loose, giving the bolt head a tap with a mallet, everything should slide out.

  4. #4
    Gone, but not forgotten Sheldon Brown's Avatar
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    Quote Originally Posted by beat_pedalr
    The bottom bracket I am trying to take out is on a Trek Tandem. It appears to be the same BB found on Trek's Soho model bicycle.

    The bottom bracket looks like this....

    I have removed the bottom bracket spindel and bearing case. The only thing left in the frame is the eccentric BB shell. I loosened/removed the main bolt but now I don't know what to do. I tried to hammer it out with a rubber mallet without success. The drive side of the shell has two hex head indentations but they don't seem to do anything. can anyone help me out with this problem?
    See: http://sheldonbrown.com/synchain.html

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