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Thread: Gear ratio

  1. #1
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    Gear ratio

    I am preparing for a very hilly 10 day bike trip. I have not had the opportunity to train as much as I had planned so I am considering switching cassettes to give me some different gear options. The current setup up on my bike is:

    Crankset Shimano Ultegra SL HollowTech II w/7075 CNC 39/53T Chainrings
    Bottom bracket Shimano Exterior Bearing System
    Front derailleur Shimano Ultegra SL F-Type
    Rear derailleur Shimano Ultegra SL
    Shifters Shimano Ultrega SL STI shifter/brake, 20-speed Flight Deck compatible
    Cassette Shimano 105 11-25T, 10-speed
    Chain Shimano 105 10-speed

    I would love recommendations for a rear cassette that will work well with this set up but will give me a couple easier gears.

    Thank you!

  2. #2
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    There are Shimano 10-speed road cassettes that will help a bit, a 12x27 and an 11x28 (and maybe the new 10-speed Tiagra 12x30) that should work with your current components. Beyond that you probably can't use your current rear derailleur since it won't (read probably won't) clear a larger cog. To go to a 32 or 34T cog you will likely need a MTB rear derailleur.

  3. #3
    Andrew R Stewart Andrew R Stewart's Avatar
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    BikePHL- (How i dislike having to title responses with some fake name...) Shimano will tell you that the max rear cog size for the Ultegra SL is 27T. A 28T will likely fit well enough. Not much more without comprimises of performance or chain wrap capicity. Andy.

  4. #4
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    Quote Originally Posted by Andrew R Stewart View Post
    BikePHL- (How i dislike having to title responses with some fake name...) Shimano will tell you that the max rear cog size for the Ultegra SL is 27T. A 28T will likely fit well enough. Not much more without comprimises of performance or chain wrap capicity. Andy.
    That's correct which is why I qualified the Tiagra 12x30 recommendation. However, several posters have reported success with 30 and even 32T cogs with Ultegra rear derailleurs if the derailleur hanger geometry and b-screw cooperate. No guarantees, of course.

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    Thank you for all the advice. I have decided just to keep it simple with the 12-27. I am cutting things a little close with my trip so i don't have time for any surprises if things did not work properly.


    Best regards,

    Brian

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