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  1. #1
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    GXP Track Crank not giving proper chainline

    Recently I had picked up an Origin 8 ultim8 GXP Track Crankset at a swap meet. The problem I am having is that the chainline they are giving me is around 50mm. Ive adjusted the spacers the way it is supposed to be but nothing seems to work. I have emailed Origin 8 and they had told me the crankset should have a 42mm chainline or very close to it.
    Im beginning to think the original GXP bb was taken out of the box and replaced with another GXP bb.

    The only fix i see is to buy another bb that has shorter cups, but dont know if there are bb with shorter cups.

    DSCN2007.jpgDSCN2008.jpgDSCN2009.jpgDSCN2014.jpg

  2. #2
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    There is no external BB with thinner cups. In any case, you'd need cups with almost zero thickness to make this work the way you want. But if a thinner BB existed, the spindle would be to long, and moving the right side in would push the left a mile out into space.

    Looking at the photo, I wonder if this might be a road crank, with the correct spindle and offset for a double chainring. In that case, the only way you'll get the right chain line is to mount the chainring to the inside of the spider.
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  3. #3
    coprolite fietsbob's Avatar
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    Perhaps move the chainring to the inside of the spider on a longer Bolt set.

    there are such chainring bolt circles to put 3 chainrings on the same bolt circle,,

    you can add longer spacers to make up for the 2 chainrings not there.

    wont have the Look, but will, perhaps, have the function ..

  4. #4
    cab horn
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    1) If that's a 68mm bb, there shouldn't be 2 x spacers on the left side for a gxp bb regardless of what the manual says
    2) That ain't a track crank, it's a generic road crank marketed as such
    Mes compaingnons cui j'amoie et cui j'aim,... Me di, chanson.

  5. #5
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    The only problem is that i cant mount the chainring on the inside of the spider unless i took a file to it. Because it has a taper and is not flat on the backside.

  6. #6
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    Yes its a 68mm bb, but the bottom bracket is a 68-73mm so in order to tighten it all the way the spacers are needed.

  7. #7
    coprolite fietsbob's Avatar
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    More Fixie stuff.. Seems a step of cutting the spider down , was not done .. as inner ring mounting not foreseen

    low price point makes compromises..

    Actual track cranks use the Old Campag 144bcd these days ..

  8. #8
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    These cranks are indeed 144bcd.

  9. #9
    coprolite fietsbob's Avatar
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    maybe they had a 135 hub chainline in mind, and you are running a 120 frame.

    maybe you will be better served with a Square Taper BB and cranks,
    there you have BB spindle length choices .
    Last edited by fietsbob; 11-19-13 at 02:13 PM.

  10. #10
    Morton Nagrom_'s Avatar
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    There should never be spacers like that using a 68mm BB.
    That prevents the spline from bottoming out and probably ruins your chainline.

    Regardless, chainline shouldn't be that big of a concern. I have honestly never measured mine. You'd probably have to be off an inch or so to get a track chain to derail off of full profile track teeth.
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  11. #11
    A little North of Hell
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    eject!

    sell it, and get a proper crankset.
    [SIGPIC][/SIGPIC]
    XXXI

  12. #12
    Constant tinkerer FastJake's Avatar
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    I agree, it looks like you got hosed on this crankset. I'd abandon it and get the right one (get something, anything better than O-8 next time...)

    Unless those spacers are indeed not supposed to be there. Then you might be ok.

    Quote Originally Posted by Nagrom_ View Post
    Regardless, chainline shouldn't be that big of a concern. I have honestly never measured mine. You'd probably have to be off an inch or so to get a track chain to derail off of full profile track teeth.
    It probably won't derail but it will run like crap. I always get my chainline on SS/FG bikes within a couple millimeters. More than that and it gets rough.
    Why "derailer" is the correct way to spell the gear-change mechanism: sheldonbrown.com/derailer.html

  13. #13
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    Quote Originally Posted by FastJake View Post
    ....It probably won't derail but it will run like crap. I always get my chainline on SS/FG bikes within a couple millimeters. More than that and it gets rough.
    Yes, chainline isn't rocket science, and being off by a few millimeters either way won't matter. But much more than that will cause friction, noise and wear, and will also cause vibration under load that you'll feel through the pedals.

    I try to avoid telling folks that they must trash stuff, which is why I suggested the wrong side mounting as a possibility. But unless you can find a way to make this work better, chucking it is your best bet.
    FB
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    An ounce of diagnosis is worth a pound of cure.

    “Never argue with an idiot. He will only bring you down to his level and beat you with experience.”, George Carlin

    “One accurate measurement is worth a thousand expert opinions” - Adm Grace Murray Hopper - USN

    WARNING, I'm from New York. Thin skinned people should maintain safe distance.

  14. #14
    7-speed doomsday prepper ThermionicScott's Avatar
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    Looks like an SS crankset to me -- there's no ledge on the tabs for an inner ring. Sounds like the BB is the wrong one.
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  15. #15
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    50mm chainline isn't always a problem. maybe look at the rear hub for an answer.

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