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  1. #1
    The Loneliest Domestique bad_mojo's Avatar
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    triple to compact

    I humbly ask your advice. My crank arm is jacked up (long embarrassing story) and needs to be replaced and I found a good deal on a compact.

    What parts would be required to switch from a triple to compact crank? What would have to be done to the front shifters?

    The triple is the stock bontrager select and the compact is a shimano ultegra on a trek 1200. Everything is pretty much stock on the Trek.

    What would make the most sense: order a new identical crank, replace with a compact, or replace the crank arm with spare parts from a LBS?
    Last edited by bad_mojo; 09-04-07 at 09:58 PM.

  2. #2
    Senior Member
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    In order of increasing cost:
    1. Replace only the damaged crank arm, particularly if it's the left crank arm.
    2. Buy a new identical crank since you can use the existing bottom bracket and no changes to the shifters or front derailleur will be needed.
    3. Change to a new compact cranks with the required bottom bracket and, possibly a new front derailleur.

    Shifter compatibility will depend on the model shifters you have. 9-speed 105 and Ultegra STIs were both double and triple compatible. 10-speed 105 is both double and triple compatible but Ultegra is specific to one or the other. However, a triple STI can be used adequately with a double crank by locking out the granny ring with the fd's inner limit screw.

  3. #3
    Senior Member capwater's Avatar
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    If you have an external bearing bottom bracket, you're good to go with just new cranks. If not you'll need to go with a new BB, 109.5 length (ie; if it's Octalink). Shifters are fine, ya might want to drop down the FD some.

  4. #4
    Elitist Troglodyte DMF's Avatar
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    Why would you replace with a compact? Do you really want worse gearing?
    Stupidity got us into this mess - why can't it get us out?

    - Will Rogers

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