Front derailleur for close ratios

Discussion in 'Cycling Equipment' started by Craig, Aug 22, 2004.

  1. Craig

    Craig Guest

    My old bike had an Exage FD with triple chainrings 28, 34, 40 (it's
    very flat where I live). I recently got a new bike with Alivio FD and
    22, 32, 42 chainrings. Moving the old chainrings to the new bike, the
    Alivio derailleur won't shift cleanly because the geometry of the cage
    is different - it has to be set higher than optimum for the big
    chainring so that it clears the middle one. Clearly it's designed for
    the bigger difference in sizes. I can't fit the old Exage one because
    the seat post diameter is different.

    What current FD would work well with these ratios? Or, if the answer
    is None, what is the minimum acceptable difference in number of teeth?

    And, when buying a new FD, how is the clamp width specified - diameter
    or seat post, or circumference?

    Thanks
     
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  2. LAN Support

    LAN Support Guest

    My wife's bike with 24-34-40 chainrings is using a Record triple FD without
    problem. I suspect that any FD intended for double chainrings would work,
    it's just that I didn't have a double FD with a 34.9mm clamp. The Deore XT
    FD that was installed with the original 26-36-48 chainrings wouldn't work
    with the 24-34-40 chainrings as the inside of the cage fouled the middle
    chainring unless the FD was raised about 1/2" above where it should be.

    Nick

    "Craig" <[email protected]> wrote in message
    news:[email protected]
    > My old bike had an Exage FD with triple chainrings 28, 34, 40 (it's
    > very flat where I live). I recently got a new bike with Alivio FD and
    > 22, 32, 42 chainrings. Moving the old chainrings to the new bike, the
    > Alivio derailleur won't shift cleanly because the geometry of the cage
    > is different - it has to be set higher than optimum for the big
    > chainring so that it clears the middle one. Clearly it's designed for
    > the bigger difference in sizes. I can't fit the old Exage one because
    > the seat post diameter is different.
     
  3. I just set up my half step plus granny touring bike with a Shimano
    Sora double front derailleur. Chainrings of 45-42-20. Shifts OK.
    Cost was about $11.50 for the derailleur from Nashbar. Surprisingly
    the derailleur is able to handle the 25 tooth difference on the front
    without the chain dragging on the bottom of the cage when in the small
    cogs in back.


    [email protected] (Craig) wrote in message news:<[email protected]>...
    > My old bike had an Exage FD with triple chainrings 28, 34, 40 (it's
    > very flat where I live). I recently got a new bike with Alivio FD and
    > 22, 32, 42 chainrings. Moving the old chainrings to the new bike, the
    > Alivio derailleur won't shift cleanly because the geometry of the cage
    > is different - it has to be set higher than optimum for the big
    > chainring so that it clears the middle one. Clearly it's designed for
    > the bigger difference in sizes. I can't fit the old Exage one because
    > the seat post diameter is different.
    >
    > What current FD would work well with these ratios? Or, if the answer
    > is None, what is the minimum acceptable difference in number of teeth?
    >
    > And, when buying a new FD, how is the clamp width specified - diameter
    > or seat post, or circumference?
    >
    > Thanks
     
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