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  1. #1
    mtbr member
    Reputation: MikeH's Avatar
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    New question here. build problem / question...

    I need some help with a 1x9 build I've been working on. (I know it's not a SS but the problem is in the 1 not the 9.)

    I bought a Trek 850 frame on Ebay (that I read about here, Thanks!) and built it up with...
    XT bottom bracket - new '03
    LX cranks - new '03
    salsa 36 tooth ring 7075 Al - new
    XT rear der.
    LX cassette
    and some other stuff that I had laying around.

    Build it up and it all works fine in the stand. Chainline is best at the 3rd or 4th smallest cog in the back.
    Take her out for the first ride things are fine, then I stand and hammer and the chain jumps off the front chainring. It will do it in the 7 smallest cogs, (the ones with the best chain line). If I am pushing on right crank the chain jumps out and if I push on left it jumps in. I am thinking something must be flexing, frame, cranks + BB, chain ring??? SO, here I am all excited to get this thing put together and not I can't ride it! Any ideas? I would really like to get this thing rolling!

    Should I get some different cranks and try that? which ones? any cheaper options? Try a different ring?

    Thanks much for the help!

  2. #2
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    HMm... this may be a bunch of BS... seeing as how I have never done a 1x9 like yours before. But..


    without resorting to a chainguide, I would try shortening the chain/tighten B tension screw. But I think that may not do much. You might be able to run a double bash guard setup. Or do the ziptie MRP roller thing(look on pinkbike for that one) Actually.. i'd try the mrp roller/ziptie first.

  3. #3
    The Top Cap Guy
    Reputation: Fast Freddy's Avatar
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    I thought the LX cranks had to be used with an LX bottom bracket for correct chainline. I bet this is your problem. If you use the wider- 2003 LX bottom bracket I bet the issues will dissappear. I mean if you were running a triple up front it would still have to stay in that gear right?

    Just my 2 cents...

    FF
    "If I'm leading, I'm bleeding."

  4. #4
    mtbr member
    Reputation: MikeH's Avatar
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    Quote Originally Posted by Fast Freddy
    I thought the LX cranks had to be used with an LX bottom bracket for correct chainline. I bet this is your problem. If you use the wider- 2003 LX bottom bracket I bet the issues will dissappear. I mean if you were running a triple up front it would still have to stay in that gear right?

    Just my 2 cents...

    FF
    I think I may order a new BB. The cranks and BB seem to work together, both are V2 octalink, I think. I am still puzzled.

  5. #5
    The Top Cap Guy
    Reputation: Fast Freddy's Avatar
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    Quote Originally Posted by MikeH
    I think I may order a new BB. The cranks and BB seem to work together, both are V2 octalink, I think. I am still puzzled.
    They are the same spline - but 03 XT cranks are designed to work of the narrow XT bottom bracket and the 03 LX is designed to work of the wider LX bottom bracket (if memory serves it's like almost 100 mm of diffrence)

    FF
    "If I'm leading, I'm bleeding."

  6. #6
    Lazy People Suck
    Reputation: Fett's Avatar
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    Quote Originally Posted by MikeH
    I need some help with a 1x9 build I've been working on. (I know it's not a SS but the problem is in the 1 not the 9.)

    I bought a Trek 850 frame on Ebay (that I read about here, Thanks!) and built it up with...
    XT bottom bracket - new '03
    LX cranks - new '03
    salsa 36 tooth ring 7075 Al - new
    XT rear der.
    LX cassette
    and some other stuff that I had laying around.

    Build it up and it all works fine in the stand. Chainline is best at the 3rd or 4th smallest cog in the back.
    Take her out for the first ride things are fine, then I stand and hammer and the chain jumps off the front chainring. It will do it in the 7 smallest cogs, (the ones with the best chain line). If I am pushing on right crank the chain jumps out and if I push on left it jumps in. I am thinking something must be flexing, frame, cranks + BB, chain ring??? SO, here I am all excited to get this thing put together and not I can't ride it! Any ideas? I would really like to get this thing rolling!

    Should I get some different cranks and try that? which ones? any cheaper options? Try a different ring?

    Thanks much for the help!
    It may be worth trying to put the front derailleur on as a chain guide without a cable and adjust the limit screws so it is centered nicely. I have a friend who has a 1x9 and he runs a jump stop on the inside and a Spot chainring guard on the outside and it keeps everything in check and looks very clean.
    "Son, The world needs ditchdiggers, too"-Ted Knight, Caddyshack

  7. #7
    Candlestick Maker
    Reputation: baker's Avatar
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    My 1x8 experience

    On my 1x8, I resorted to a jumpstop on the inside and a shaved down big
    ring on the outside. This eliminated chain dropping probs for me.

    baker

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