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  1. #1
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    Road/MTB compatibility

    I'm a beginner in bike building and may have messed up. I wanted a commuting/light touring bike with the ability to take fatter tyres for occasional off-road compatibility. I wanted dropped bars but with MTB-type drivechain for the lower gearing. Having read various FAQ and postings I got the impression that most Shimano stuff is cross-compatible. Fired with unjustified confidence, I fitted my frame with:


    Dura-Ace 7900 bar-end shifters
    Deore XT FD-M780 Triple Conventional Swing Dual Pull Front Derailleur
    Deore XT RD-M780 Shadow 10 Speed Top Normal Rear Derailleur
    XT M780 10 Speed Hollowtech II Triple Chainset
    Shimano 11-32 10-speed cassette
    HG-X chain

    However, I can't persuade either the front or rear derailleur to shift properly - the rear only gives me access to gears 2-8, and the front DR won't change at all.

    Please help! Have I possibly installed these components incorrectly or are they incompatible. Is there any way to make these parts work together? If not, what part(s) should I change?

    Many thanks,
    Andy

  2. #2
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    Can't answer for your setup specifically but I have a road bike setup with drop bars and mountain bike drive train. I have 10 speed 6700 STI levers operating xtr derailleurs BUT the rear deralleur has to be a 9 speed (shimano road 10 speed and MTB 10 speed are not directly compatable, different cable pull ratios especially on the rear).
    The front should work though ?, mine has xtr front mech which works, not perfect but works (I get a bit of chain rub on either highest or lowest gear depending on how its set up)

  3. #3
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    Yes, on trawling the web the consensus is that the 10 speed shifters won't work with a 10 speed rear DR as the pull ratio is different. Not clear why the front changer isn't working. I've decided that the best and cheapest solution will be to replace the bar end shifters with xt trigger types. This may mean also moving to a straight bar but I can put both the drop bars and their shifters on my road bike with more confidence of success. I can evenprertend that's what I intended all along.

    Cheers

  4. #4
    Nouveau Retrogrouch SuperModerator
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    Road/MTB compatibility

    Quote Originally Posted by Hillsidebeer View Post
    Yes, on trawling the web the consensus is that the 10 speed shifters won't work with a 10 speed rear DR as the pull ratio is different. Not clear why the front changer isn't working. I've decided that the best and cheapest solution will be to replace the bar end shifters with xt trigger types. This may mean also moving to a straight bar but I can put both the drop bars and their shifters on my road bike with more confidence of success. I can evenprertend that's what I intended all along.

    Cheers
    Shimano mtb 10-sp is compatible with nothing but itself.

    There is no 7900 barend shifter. They are BS78 or BS79.

    The front barend shifter should work though. It is friction, not indexed.
    mtbtires.com
    The trouble with common sense is it is no longer common

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