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  1. #1
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    move FD when converting from 3x9 to 2x9?

    Hi - I've got a Shimano 3x9 drive on a Jet9 29er. I'm considering replacing the big ring with a bash guard and leaving the 22 and 32 rings as is. I would like to optimize chain-line and gear range for this. Currently when on the 22 chainring and shifting into smaller cogs on the back, the chain begins to hit the FD low cross bar at about the middle of the cassette.

    Can I move the FD lower on the frame with no big chainring and keep the same good shifting. The Jet9 build also requires 2 spacers on the XT crank on the drive side. Should I get rid of 1 and/or move it to the non-drive side to optimize the chain-line for the smaller chainrings?

    Thanks.

    Chris

  2. #2
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    Quote Originally Posted by cjcrawford
    Hi - I've got a Shimano 3x9 drive on a Jet9 29er. I'm considering replacing the big ring with a bash guard and leaving the 22 and 32 rings as is. I would like to optimize chain-line and gear range for this. Currently when on the 22 chainring and shifting into smaller cogs on the back, the chain begins to hit the FD low cross bar at about the middle of the cassette.

    Can I move the FD lower on the frame with no big chainring and keep the same good shifting. The Jet9 build also requires 2 spacers on the XT crank on the drive side. Should I get rid of 1 and/or move it to the non-drive side to optimize the chain-line for the smaller chainrings?

    Thanks.

    Chris
    If it is possible, move the FD down. It likely will improve the shifting. But you do not need to and you may have the FD hit the swing arm or bash ring if you move it.

    I always like to move the chainrings as far inboard as possible. Again, watch for clearance problems. Chainrings to frame. FD and chain to tire.
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  3. #3
    dwt
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    I recently made the exact change and am running bash-32-22. I left the derailleur where it was, at the height for clearance of a 44T, and all I did was adjust the limit screw to stop on the 32T.

    It does look a bit funky to have the derailleur that far above the outer ring. But I have a top swing derailleur and even if I want to lower it to the "proper" height, I can't. So rather than lower it a little, I just left it, and it shifts just fine.
    Old enough to know better. And old enough not to care. Best age to be.

  4. #4
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    Not trying to hijack this, but i did the same a couple of years ago, and I can't get my FD to not rub the chain in 32 front and smaller cogs in the back, or if I fix that, then 22 front and the bigger cogs in the back.

    Any ideas?
    My name is Chris and I ride a Prophet 650b with a Lefty.

  5. #5
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    Where is the chain rubbing in these two cases? inboard plate, outboard plate, bottom rear connecting pin?

    Chris

  6. #6
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    It rubs just above the connector screw on the inner plate when in the big cogs in the back while in small chainring, or on the outer plate when on the small cogs in the back on larger chainring. Notice that I did not say "and" when describing the scenarios. I can adjust the FD to rub high or low, not both.
    My name is Chris and I ride a Prophet 650b with a Lefty.

  7. #7
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    Quote Originally Posted by Prophet Julio
    It rubs just above the connector screw on the inner plate when in the big cogs in the back while in small chainring, or on the outer plate when on the small cogs in the back on larger chainring. Notice that I did not say "and" when describing the scenarios. I can adjust the FD to rub high or low, not both.
    Have to tried adjusting the limit screws?
    Making your adjustments starting with the shifter in the middle position?
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  8. #8
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    The range the FD moves from the small ring to the middle ring does not change just because you take the big ring off. Therefore I think the problem is your limit screws and the initial starting position for the FD with no tension on the cable. It sounds like you are not starting inboard enough with the FD. Release the cable and play with that limit screw to let the FD inboard just enough to prevent rub on the inner plate then re-tension the cable and screw it down so this is your new "start point" for the upward shift.

    Chris



    Chris

  9. #9
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    When I set it up, I put it on the small front and the large rear cog. Then I slacked the cable and adjusted the limit screw until it didn't rub. Then I set the cable tension. Then I shifted to the larger chainring and the smallest cogs in the back. Rub, rub, rub. I can push the derailleur out enough to stop the rubbing, because the limit screw is not the limit when I shift to the larger chainring. It just seems that the FD does not "index" enough to cover the full range. If I change the throw by adjusting the barrel to prevent rub when on the larger chainring, then I get rubbing in the smaller chainring. I'm thinking I should just replace the FD and see if that fixes it. It is 5 years old with lots of hard use, sticks, twigs and the like.
    My name is Chris and I ride a Prophet 650b with a Lefty.

  10. #10
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    Ok, I see what you mean. I can only recommend trying some radial rotation of the FD and/or taking a pliers to the plates. On some road bikes with a similar problem, I took the FD plate pin out and put a wider spacer in to widen the gap a mm or so. In one instance, it fixed it!

    Chris

  11. #11
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    Thanks for the advice. I have already widened the plates as you suggested. Maybe there is something in the derailleur that is preventing full movement. Time to rip it apart and achieve shifting Nirvana again!
    My name is Chris and I ride a Prophet 650b with a Lefty.

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