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  1. #1
    Hooha!! All American 6's Avatar
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    Frame Design Question

    Road Frame:

    Why do some builders (Cannondale/some Santana/others) have the top tube connected to the lateral tube instead of the head tube?

    What are the advantages/disadvantages?

    Is this desirable?

    Is there a name for this frame design?

    AA6





    Thanks Craiglist for selling my Burley/Piccolo in less then a week!
    04 Cannondale CAAD 7
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  2. #2
    hors category TandemGeek's Avatar
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    Quote Originally Posted by All American 6 View Post
    Why do some builders (Cannondale/some Santana/others) have the top tube connected to the lateral tube instead of the head tube?
    One of two primary reasons:

    1. To provide the captain with more standover height than would otherwise be possible with a conventional, un-stepped top tube on their smaller road and off-road tandems while still providing some additional, internal bracing in the front triangle and a relatively tall head tube to support somewhat higher handlebar positioning often times favored by tandem captains. The alternative is to use a highly compact frame design similar to what's now showing up on the lateral-less (or as I prefer to call them, top (tube) less) tandems from Paketa, Calfee, Co-Motion, etc... You'll find a similar, steeply sloping top tube on most Erickson tandems.

    2. To simplify the lines of a tandem's horizontal top tube to support convertible (aka. cabrio) multi-seat tandems that can be converted from two seat to three seat, four seat and/or five seat configurations. This also affords the captain additional standover height which, again, may be desireable on a multiseat tandem, as well as additional front triangle bracing. The alternative (or at least one of the alternatives) is to use an even more radical design.

    Quote Originally Posted by All American 6 View Post
    What are the advantages/disadvantages?
    Advantages: As mentioned above. Moreso when used on off-road tandems where 3" or more of standover height is desireable.

    Disadvantages: Functionally, none. Aesthetically... that's somewhat subjective.

    Quote Originally Posted by All American 6 View Post
    Is this desirable?
    Only if you need or want more distance between the top tube and your "boys" and/or are considering a convertible multi-seat tandem. If you need a smaller size Santana or Cannondale it is what it is, unless you opt to go with a custom-framed Santana. Cannondale does not do one-offs.

    Quote Originally Posted by All American 6 View Post
    Is there a name for this frame design?
    I've always referred to it as a "stepped" top tube.

    If you're interested in seeing just how many different ways there are to design a frame to accommodate riders of varying heights, or what a multi-seater would look like if it was designed without a continuous, horizontal top tube, take a look at a few Ventana El Conquistadors...
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    Last edited by TandemGeek; 07-19-07 at 12:56 PM.

  3. #3
    Senior Member zonatandem's Avatar
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    Standover room is the primary reason.
    Here's a different aproach on our Zona tandem.
    Drastically sloping top tube. Lateral blends into the downtube.
    Aestethics are a personal issue . . .
    Pedal on TWOgether!
    Rudy and Kay/zonatandem
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