Need Help re-gearing with a RD6870
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  1. #1
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    Question Need Help re-gearing with a RD6870

    I have a 2016 Specialized Tarmac Pro Disc (Di2). It came with a S-Works 52-36 Mid Compact and a short throw 6870 Rear Deraileur driving an 11-28.
    On many hills hear where I live I cannot keep up the Cadence I would like.
    Would going to a 11-30t on the back make a noticable difference? And would this work with my deraileur?
    Otherwise or is it preferred to change the front rings to a 50-34t. Do I need to change all? or can I use my Hidden Bolt 110BCD spider and BB I just buy new rings?
    Or Do I really need to go to the 50-34t and a 11-30t to really make a difference.

    Advise would be appreciated!

    Gary

  2. #2
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    I see a new bike in your future, Canyon's are nice, that's what I got.
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  3. #3
    'brifter' is a lame word.
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    Quote Originally Posted by gzim View Post
    I have a 2016 Specialized Tarmac Pro Disc (Di2). It came with a S-Works 52-36 Mid Compact and a short throw 6870 Rear Deraileur driving an 11-28.
    On many hills hear where I live I cannot keep up the Cadence I would like.
    Would going to a 11-30t on the back make a noticable difference? And would this work with my deraileur?
    Otherwise or is it preferred to change the front rings to a 50-34t. Do I need to change all? or can I use my Hidden Bolt 110BCD spider and BB I just buy new rings?
    Or Do I really need to go to the 50-34t and a 11-30t to really make a difference.


    Advise would be appreciated!

    Gary
    How can any of us know what you need?

    If you really need that much help you should get a GS rear derailleur (RD 8070 GS) and an 11-34 cassette.
    I work for some bike racers
    I've got some bikes, some guns,
    and a bunch of skateboards

  4. #4
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    Quote Originally Posted by gzim View Post
    I have a 2016 Specialized Tarmac Pro Disc (Di2). It came with a S-Works 52-36 Mid Compact and a short throw 6870 Rear Deraileur driving an 11-28.
    On many hills hear where I live I cannot keep up the Cadence I would like.
    Would going to a 11-30t on the back make a noticable difference? And would this work with my deraileur?
    Otherwise or is it preferred to change the front rings to a 50-34t. Do I need to change all? or can I use my Hidden Bolt 110BCD spider and BB I just buy new rings?
    Or Do I really need to go to the 50-34t and a 11-30t to really make a difference.

    Advise would be appreciated!
    I would advise you to take this advice: percentages are percentages. A 2 tooth change in the front means a 5.6% lower gear. That's about 4 rpm at a 70 rpm climbing cadence. A 2 tooth change in the back means 7.1% lower gear, or 5 rpm. Changing both means a 13.4% change and about 9 rpm. Whether either or both of these is enough for you, only you can tell. Obviously changing the cassette is cheaper, though it would result in bigger jumps between gears. Ask yourself whether there is really any situation where you actually "need" the 11t cog; most often by the time you get into a gear that big you will go just as fast coasting in a tight tuck.

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