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Thread: 2x9 issues

  1. #1
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    2x9 issues

    I am currently running an 07 XT crank (without the granny), seems to work well enough... when Im not getting chain drops. I think Im getting chain drops when Im in the middle ring because the crank was spec'ed with a 50mm chainline, and my frame seems to only work well with 47.5mm chainlines.

    Im thinking of just getting an Ultegra triple and just dumping the largest chainring, I will be left with 39/29. Will that work? Or do I have to look for some other 2x9 specific crank?

    Appreciate any help...

  2. #2
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    Just a few thoughts:

    Did you double check to make sure you have the appropriate bottom bracket spacer setup for the shell width of your bike?

    If it dumps when you're in little in back/middle up front, then have you checked the limits on your front derailleur?

    Don't know if that helps but that's where I would start.

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    oops - no message
    will there be beer?

  4. #4
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    Quote Originally Posted by Quest13
    I am currently running an 07 XT crank (without the granny), seems to work well enough... when Im not getting chain drops. I think Im getting chain drops when Im in the middle ring because the crank was spec'ed with a 50mm chainline, and my frame seems to only work well with 47.5mm chainlines.

    Im thinking of just getting an Ultegra triple and just dumping the largest chainring, I will be left with 39/29. Will that work? Or do I have to look for some other 2x9 specific crank?

    Appreciate any help...
    You can get a 42 middle ring too for the ultgra if you think you need it. Should work fine. If you end up with the 39 as your big, consider a 26 or 28 small so you have a little more range.

    G
    You can't depend on honest answers from dependant hands...

  5. #5
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    two thoughts.

    The ultegra crankarms will probably hit your chainstays. Thats what happened the last time I tried to put a road crank on a mountain bike

    Theres spacers on the external bearings that you can use to adjust chainline. The main mechanic at the bike shop I work is running a 2x9 on an XT crank by running all the spacers to the non-drive side. It works well for him.

  6. #6
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    Quote Originally Posted by msrothwe
    two thoughts.

    The ultegra crankarms will probably hit your chainstays. Thats what happened the last time I tried to put a road crank on a mountain bike

    Theres spacers on the external bearings that you can use to adjust chainline. The main mechanic at the bike shop I work is running a 2x9 on an XT crank by running all the spacers to the non-drive side. It works well for him.
    Does this not throw the crank arms out of center with the bottom bracket shell? When you move the drive side closer in the non-drive has to move out by the same amount. Also, it seems like the bottom bracket bearing on the non-drive side wouldn't have as many threads in the shell. Not a HUGE deal since it's non-drive, but still...I wouldn't go this route, personally.

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    Quote Originally Posted by AggieXCRacer
    Does this not throw the crank arms out of center with the bottom bracket shell? When you move the drive side closer in the non-drive has to move out by the same amount. Also, it seems like the bottom bracket bearing on the non-drive side wouldn't have as many threads in the shell. Not a HUGE deal since it's non-drive, but still...I wouldn't go this route, personally.
    crankarms are almost never centered anyways.

    as for the lack of threads...They are the same. The reason that there is spacers is for 73mm bottom bracket shells, so they have to be the same. The spacer is just there for chainline.

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    just throw your granny back on, its only 10 grams.

    or , get one of those chain keepers. they are about 30 grams.

  9. #9
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    Quote Originally Posted by msrothwe
    crankarms are almost never centered anyways.

    as for the lack of threads...They are the same. The reason that there is spacers is for 73mm bottom bracket shells, so they have to be the same. The spacer is just there for chainline.

    I agree. I believe this setup can work for you because it works for me. I'm running the same setup on a scott scale 40. Had to do some tinkering to get the optimal chainline and it took me a little while to figure it out but I was determined and the persistance paid off. I got a couple of shims off of a XT bb because they were thinner than the ones that came with the XTR bb from the my lbs at no cost. I put one of the thin XT shims on the drive side and two of the thicker XTR shims on the non-drive side and it worked. The middle ring is really close to the frame and I wondered if it would work but it did. I also put the smallest shim that i could find behind the rear cassette to further improve the chainline and increase shifting performance. I am running a 44, 34 up front and a 11-34 in the back and it shifts flawlessly. I'm not saying that this will work for you but it does for me. Maybe this will help you save some time and some cash. Best of luck

  10. #10
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    Quote Originally Posted by J.Mc.
    I agree. I believe this setup can work for you because it works for me. I'm running the same setup on a scott scale 40. Had to do some tinkering to get the optimal chainline and it took me a little while to figure it out but I was determined and the persistance paid off. I got a couple of shims off of a XT bb because they were thinner than the ones that came with the XTR bb from the my lbs at no cost. I put one of the thin XT shims on the drive side and two of the thicker XTR shims on the non-drive side and it worked. The middle ring is really close to the frame and I wondered if it would work but it did. I also put the smallest shim that i could find behind the rear cassette to further improve the chainline and increase shifting performance. I am running a 44, 34 up front and a 11-34 in the back and it shifts flawlessly. I'm not saying that this will work for you but it does for me. Maybe this will help you save some time and some cash. Best of luck
    I'm sorry, i misread your original post. Thought you said you had a XTR crank. The same principle still applies. Go to your local lbs and see if they'll hook you up with some shims that are either thicker or thinner than the ones you already have and give it a go. Be prepared to take the crank on and off several times to get the right setup. As I said before, maybe this will save you some time and money.

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    Thanks for all the help guys, guess I will try to fiddle with the spacers to get a better chainline.

    Btw are crankarms never really centered?

  12. #12
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    Quote Originally Posted by Quest13
    Thanks for all the help guys, guess I will try to fiddle with the spacers to get a better chainline.

    Btw are crankarms never really centered?
    Not sure if i'm understanding exactly what it is your asking but it's not possible or at least i dont think it is possible due to the chainrings on the drive side pushing the crankarm out further away from the centerline of the bike. Maybe you could make your own bb and extend the length on the non-drive side and put equal amount of spacers to center the crankset with the centerline of the bike but that's not practical. Hope this helps.

  13. #13
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    Quote Originally Posted by Quest13
    Thanks for all the help guys, guess I will try to fiddle with the spacers to get a better chainline.

    Btw are crankarms never really centered?
    You could also go with a 26 or 28 granny and put a 38-42 big in the middle. Might be the easiest and I bet you'd like the range of a little smaller "small ring" than a 29-32.

    G
    You can't depend on honest answers from dependant hands...

  14. #14
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    Quote Originally Posted by J.Mc.
    Not sure if i'm understanding exactly what it is your asking but it's not possible or at least i dont think it is possible due to the chainrings on the drive side pushing the crankarm out further away from the centerline of the bike. Maybe you could make your own bb and extend the length on the non-drive side and put equal amount of spacers to center the crankset with the centerline of the bike but that's not practical. Hope this helps.
    Right, that makes sense, but what about where the pedals are located? The drive side crankarm could be shaped slightly different so that the pedals are both the same distance from the centerline of the bike, right?

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    Quote Originally Posted by AggieXCRacer
    Right, that makes sense, but what about where the pedals are located? The drive side crankarm could be shaped slightly different so that the pedals are both the same distance from the centerline of the bike, right?
    not always. Some bottom brackets are symmetrical, however, most bb's are not. look at the distance from the crankarm to the chainstay. I'm almost certain that its not the same from side to side.

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