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Rear Derailleur Sizes- What's the formula?

Started by Mark · · Last activity · 7 posts · 606 views

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Cycling Equipment
Published
8 April 2004
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14 April 2004
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Mark
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  1. Hi Folks, Please forgive me if this question has recently
    been posed to you all.

    I'm not too confused about Front Derailleur types, as I do
    understand you basically don't use a "double front"
    Derailleur with a "triple Chainring" set.

    But I am confused about what properly determines what size
    Rear Derailleur Cages should be used in any given instance?
    (Short-Medium-Long)

    How would I know what size Derailleur Cage I need if I went
    with a 9 Speed Campy Chorus, or 9 Speed Campy Centaur group
    on a road bike? Is it the Cassette Size that determines what
    size cage to use? Or?

    Forgive me for my lack of knowledge on this subject, but I
    would like to learn what determines the proper selection of
    cage size. TIA Mark
    D.

  2. Quoted post said:

    Originally posted by Mark
    Hi Folks, Please forgive me if this question has recently
    been posed to you all.

    I'm not too confused about Front Derailleur types, as I do
    understand you basically don't use a "double front"
    Derailleur with a "triple Chainring" set.

    But I am confused about what properly determines what size
    Rear Derailleur Cages should be used in any given instance?
    (Short-Medium-Long)

    How would I know what size Derailleur Cage I need if I went
    with a 9 Speed Campy Chorus, or 9 Speed Campy Centaur group
    on a road bike? Is it the Cassette Size that determines what
    size cage to use? Or?

    Forgive me for my lack of knowledge on this subject, but I
    would like to learn what determines the proper selection of
    cage size. TIA Mark
    D.

    The total amount of chain wrap-up required is what determines what cage length you should use. The wrap-up is the difference between biggest and smallest chainrings plus the difference between biggest and smallest rear cogs. For example, if you run a 39x53 double up front with a 12-27 cassette, you would need a chain wrap-up capability of (53-39)+(27-12) or 29 links.

  3. Mark said:

    How would I know what size Derailleur Cage I need if I
    went with a 9 Speed Campy Chorus, or 9 Speed Campy Centaur
    group on a road bike? Is it the Cassette Size that
    determines what size cage to use? Or?

    It's the combination of cassette and chainrings.

    See campagnolo.comgroupsets.php

    ~PB

  4. (Mark) said:

    How would I know what size Derailleur Cage I need if I went
    with a 9 Speed Campy Chorus, or 9 Speed Campy Centaur group
    on a road bike? Is it the Cassette Size that determines
    what size cage to use? Or?

    The chain needs to be of a length so that the largest ring
    and cog can be engaged and ridden. That given, the rear
    derailleur must be long enough to not drag on the bottom of
    the rear derailleur when in the small/small combination.
    Additionally, the top derailleur pulley should not hit the
    largest cog when in the small ring and largest cog.

    YOu can't just look at gear sizes to find out what length
    chain is needed. The length of the chainstay is also a
    determinent.

    No formula.

  5. apoman-<< How would I know what size Derailleur Cage I need
    if I went with a 9 Speed Campy Chorus, or 9 Speed Campy
    Centaur group on a road bike? >><BR><BR>

    Here's what they recommend altho it's not as strict as
    they imply.

    Double crank-cogs to 13-26-short Double crank-13-28-medium
    cage TYriple crank-cogs to 13-26-medium cage triple crank-13-28-
    long cage.

    BUT you can use a short cage with a double and 13-28 and you
    can use a long cage with any setup-

    Peter Chisholm Vecchio's Bicicletteria 1833 Pearl St.
    Boulder, CO, 80302
    (303)440-3535 vecchios.comvecchios.com "Ruote convenzionali
    costruite eccezionalmente bene"

  6. To add to Peter's comment about the universality of app. for
    long cage, the old tale of slower shifting with long cage is
    truly old. Mountain bikers shift as quickly as anyone. this
    is especially true in the small/small extremes as the
    tension on the long cage is higher in those combos. Tom

    --
    Bruni Bicycles
    "Where art meets science"
    brunibicycles.com
    410.426.3420
    Qui si parla Campagnolo <[email hidden]> wrote in message
    "]news:[email hidden]...

    Quoted message said:

    apoman-<< How would I know what size Derailleur Cage I need if I went with


    a 9

    Quoted message said:

    Speed Campy Chorus, or 9 Speed Campy Centaur group on a road bike?

    Quoted message said:

    <BR><BR>

    Here's what they recommend altho it's not as strict as they imply.

    Double crank-cogs to 13-26-short
    Double crank-13-28-medium cage
    TYriple crank-cogs to 13-26-medium cage
    triple crank-13-28-long cage.

    BUT you can use a short cage with a double and 13-28 and you can use a


    long

    Quoted message said:

    cage with any setup-

    Peter Chisholm
    Vecchio's Bicicletteria
    1833 Pearl St.
    Boulder, CO, 80302
    (303)440-3535
    vecchios.comvecchios.com
    "Ruote convenzionali costruite eccezionalmente bene"

  7. On 09 Apr 2004 13:13:19 GMT, [email hidden] (Qui si parla

    Campagnolo ) said:

    BUT you can use a short cage with a double and 13-28 and
    you can use a long cage with any setup-

    ...and I can use a short cage Shimano 105 with a triple (30-42-
    52) and 11-27 cassette. No droop. The derailer is pretty
    wound up in small-small and pretty stretched in big-big, but
    nothing will break if I accidentally use either combo.
    --
    Rick Onanian

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