vintage frame size nomenclature -- English/metric disconnect

Discussion in 'Cycling Equipment' started by Lin Osborne, May 7, 2003.

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  1. Lin Osborne

    Lin Osborne Guest

    Folk,

    http://www.vintage-trek.com/images/trek/84Trek_23.jpg shows something I remember but have never
    understood.

    The geometry table references frame sizes in inches, but the seat tube lengths are measured in cm.
    The confounding piece is that, when running the measures through english -> metric conversion
    factors, the numbers clearly don't correspond.

    In other words, Trek said that a 22.5" bicycle had a seat tube lenght of 56.0 cm.

    22.5" * 2.54 = 51.15 cm

    Can anyone explain this?

    Thanks, Lin
     
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  2. Lin Osborne

    Lin Osborne Guest

    Lin Osborne wrote: .
    >
    > 22.5" * 2.54 = 51.15 cm
    >

    Numbers have conspired against me.
    22.5 * 2.54 = 57.15

    Sorry, Lin
     
  3. In article <[email protected]>, Lin Osborne <[email protected]> wrote:
    >Folk,
    >
    >http://www.vintage-trek.com/images/trek/84Trek_23.jpg shows something I remember but have never
    >understood.
    >
    >The geometry table references frame sizes in inches, but the seat tube lengths are measured in cm.

    Bike sizes are all nominal until you get out a tape measure.

    > The confounding piece is that, when running the measures through english -> metric conversion
    > factors, the numbers clearly don't correspond.
    >
    >In other words, Trek said that a 22.5" bicycle had a seat tube lenght of 56.0 cm.
    >
    >22.5" * 2.54 = 51.15 cm
    >
    >Can anyone explain this?

    Bad math.

    --Paul
     
  4. Paul Southworth <[email protected]> wrote:
    > Lin Osborne <[email protected]> wrote:

    > >http://www.vintage-trek.com/images/trek/84Trek_23.jpg shows something I remember but have never
    > >understood.
    > >
    > >The geometry table references frame sizes in inches, but the seat tube lengths are
    > >measured in cm.

    > Bike sizes are all nominal until you get out a tape measure.

    > > The confounding piece is that, when running the measures through english -> metric conversion
    > > factors, the numbers clearly don't correspond.
    > >
    > >In other words, Trek said that a 22.5" bicycle had a seat tube lenght of 56.0 cm.
    > >
    > >22.5" * 2.54 = 51.15 cm

    [emended to 22.5" = 57.15 cm]

    As it happens I have a 22.5" 1984 Trek. The 22.5" measure is center-top of the seat cluster or top
    tube, the 56cm seat tube is center to center. Top tubes were 1" diameter on most steel bikes of
    this vintage and seat clusters/tubes did not stick up above the top tube. Neither is true of most
    new bikes.

    The Trek brochure referenced above shows seat tube length "A" as measured c-t, but it's really c-c.
     
  5. A Muzi

    A Muzi Guest

    "Lin Osborne" <[email protected]> wrote in message news:[email protected]...
    > Folk,
    >
    > http://www.vintage-trek.com/images/trek/84Trek_23.jpg shows something I remember but have never
    > understood.
    >
    > The geometry table references frame sizes in inches, but the seat tube lengths are measured in cm.
    > The confounding piece is that, when running the measures through english -> metric conversion
    > factors, the numbers clearly don't correspond.
    >
    > In other words, Trek said that a 22.5" bicycle had a seat tube lenght of 56.0 cm.
    >
    > 22.5" * 2.54 = 51.15 cm
    >
    > Can anyone explain this?

    Your arithmetic is in error.
    2.54 * 22.5 is 57, or more closely 57.15 cm

    (One might quickly estimate 22.5*2=45 plus half that (eleven) gives 56-plus-something; so you know
    the 51cm value cannot be right)

    However you needn't use pencil and paper next time. Just get an analog metric/inch calculator (a
    dual-scale tape measure).
    --
    Andrew Muzi http://www.yellowjersey.org Open every day since 1 April 1971
     
  6. On Wed, 07 May 2003 16:10:13 +0000, Lin Osborne wrote:

    > Folk,
    >
    > http://www.vintage-trek.com/images/trek/84Trek_23.jpg shows something I remember but have never
    > understood.
    >
    > The geometry table references frame sizes in inches, but the seat tube lengths are measured in cm.
    > The confounding piece is that, when running the measures through english -> metric conversion
    > factors, the numbers clearly don't correspond.
    >
    > In other words, Trek said that a 22.5" bicycle had a seat tube lenght of 56.0 cm.
    >
    > 22.5" * 2.54 = 51.15 cm
    >
    > Can anyone explain this?

    Yeah, you're wrong. 22.5*2.54 = 57.15. The 1.15cm is the difference between c-c and c-t measurement.

    --

    David L. Johnson

    __o | Some people used to claim that, if enough monkeys sat in front _`\(,_ | of enough
    typewriters and typed long enough, eventually one of (_)/ (_) | them would reproduce the
    collected works of Shakespeare. The internet has proven this not to be the case.
     
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