56T chainring

Discussion in 'Triathlon' started by Jim Quinn, Apr 21, 2003.

  1. Jim Quinn

    Jim Quinn Guest

    Does the Dura Ace 56T time trial chainring have to be matched with a similar small chainring or can
    it be used with a standard 42 or 39 chainring?
     
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  2. Rod Richeson

    Rod Richeson Guest

    Shimano and every bike shop says it can't/shouldn't be done. I have a
    39/56 on my Cervelo. Looked for a 42 or 44 but don't want to pay full retail for one. Mine shifts
    very well up, but sometimes downshifting it doesn't engage completely for a 1/4 to 1/2
    revolution.

    TriRod IMC 2002 IMUSA CdA 2003

    Jim Quinn wrote:
    > Does the Dura Ace 56T time trial chainring have to be matched with a similar small chainring or
    > can it be used with a standard 42 or 39 chainring?
     
  3. Billx

    Billx Guest

    How many watts would it take to push a 56 x 12 at 100RPM on the flats into a null wind for a 160-170
    lbs rider? For a 700cc wheel what speed would that work out to?

    Rod Richeson wrote in message <[email protected]>...
    >Shimano and every bike shop says it can't/shouldn't be done. I have a
    >39/56 on my Cervelo. Looked for a 42 or 44 but don't want to pay full retail for one. Mine shifts
    > very well up, but sometimes downshifting it doesn't engage completely for a 1/4 to 1/2
    > revolution.
    >
    >TriRod IMC 2002 IMUSA CdA 2003
    >
    >Jim Quinn wrote:
    >> Does the Dura Ace 56T time trial chainring have to be matched with a
    similar
    >> small chainring or can it be used with a standard 42 or 39 chainring?
    >>
    >
     
  4. BillX wrote:
    > How many watts would it take to push a 56 x 12 at 100RPM on the flats into a null wind for a
    > 160-170 lbs rider? For a 700cc wheel what speed would that work out to?

    Lots. That's probably why he's asking about the 39T small chainring option.
     
  5. Andy Coggan

    Andy Coggan Guest

    "BillX" <[email protected]> wrote in message news:[email protected]...
    > How many watts would it take to push a 56 x 12 at 100RPM on the flats into
    a
    > null wind for a 160-170 lbs rider? For a 700cc wheel what speed would
    that
    > work out to?

    Why do you assume that the original poster will be pairing that 56 tooth chainring with a 12 tooth
    cog? For that matter, why do you assume that they wish to pedal at 100 rpm?

    Andy ("55 x 12 at 78 rpm = 300 W and 28 mph") Coggan
     
  6. Billx

    Billx Guest

    Most road cyclists find a cadence of 90-110 rpm on the flats to be optimal although there are some
    like yourself who find a lower cadence like 80 rpm to be more effective. I'd assumed that someone
    wouldn't use a 56x12 on the flats unless they could push 90 rpm or better in that gear.

    Andy Coggan wrote in message
    >"BillX" <[email protected]> wrote in message news:[email protected]...
    >> How many watts would it take to push a 56 x 12 at 100RPM on the flats
    into
    >a
    >> null wind for a 160-170 lbs rider? For a 700cc wheel what speed would
    >that
    >> work out to?
    >
    >Why do you assume that the original poster will be pairing that 56 tooth chainring with a 12 tooth
    >cog? For that matter, why do you assume that they wish to pedal at 100 rpm?
    >
    >Andy ("55 x 12 at 78 rpm = 300 W and 28 mph") Coggan
     
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