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  1. #1
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    Mojo + XTR front + Noir crankset lower link rub or chain rub issue ?

    I have an XTR front derailleur and find that is sits really close to the lower link - so much that I could not have it strait without rubbing the lower link during compression (I have scrub marks), so it was somewhat angled back towards the rear. But then I would get chain rub in granny + the last 4 of the smallest cogs (hitting the other side of the derailleur guide) and even some rub in middle+small cog (I use a 2x9 with bash ring so that's my only choice for fast speed).

    Has anyone else run into this ?

    I ended up dreming some of the metal out of the front derailleur (lower corner) to make it fit more straight and clear the Mojo lower link. Next problem is that now I get really bad chain rub in granny + big cog.

    I adjusted the lower screw and cable tension to as loose as possible and it barely clears it now. Since I'm using 2x9 setup, I was thinking of offsetting the drive side out a bit to help with chainline, and making it easier to go into granny. I'm using a Truvativ Noir crankset which came with 2x2.5mm spacers, one for each side (68 of the Mojo -> 73mm GXP BB).
    I got a 1mm spacer and added to drive side (so 2.5/3.5).

    I now can pretty much use all the rear cog with the granny or middle ring with no chain rub (SRAM 971) YEAH - but I get a bit of play in the crankarms, and things are tight... wondering of the longer BB is causing the crankarms to not be tight correctly. I destroyed the GXP external thread using a dedicated flat tool with almost a full circle of teeth, and just ordered partool BBT19 to see if I get better grip with full 36 teeth contact and deeper grip (plus I can torque it correctly this time).

    Anyone has same setup and what was your trick to make it work ?
    As there better dedicated 2x9 front derailleur or can I make my XTR work ?

    here is my setup (shown with old shimano chain)
    Last edited by adumesny; 10-31-2010 at 09:24 AM.

  2. #2
    Singletrack Addict!!!
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    I'm using the same set-up, but the derailleur is the 970, chain rings 26/34. I wouldn't use that 1mm spacer, the left crank arm needs to seat all the way in the spindle in order to tighten, otherwise you risk damaging the arm and then having the "loose arm issue". I have the derailleur sit as close as possible to the links, I'll get a little chain rubbing when on the 34 and the 2 smallest rear cogs, but just slightly. On the 26 no rub at all. I don't know if the cage on your XTR is an different from mine.
    The world needs a huge socio-economic change...be it. We all need to ride more....

  3. #3
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    My XTR is a 961, so yes it might have a different profile. I know I had to grind it down near the bottom elbow to make it fit closer to the Mojo lower link...

    as for the spacer, yeah it makes sense and I will try taking out the 1mm to see if that's what it was. If so I might just reduce the left hand side by 1mm to make up for it as I suspect offseting the entire thing to the drive side by 1mm wouldn't cause issues.

    It's just annoying to have any kind of grindings at either extremes (granny+Big cog, or mid ring + smallest cog) since there are no replacement for those ratio in a 2x9, and I use them both quite a bit.

  4. #4
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    I removed the 1mm spacer, and put in a new GXP (had to take old one with a plumbing wrench as the teeth were worn out by the last tool). The play is gone, and I still can shift to all the 2x9 gears with no rub other than granny+2 smallest cog, which I can live with....

  5. #5
    Singletrack Addict!!!
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    Great, now just go and ride the hell out of it!!
    The world needs a huge socio-economic change...be it. We all need to ride more....

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