How close to rear wheel on P3?

Discussion in 'Cycling Equipment' started by John Crankshaw, Nov 29, 2003.

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  1. I'm helping a friend build a Cervelo P3 TT bike.

    Wondering how close to mount the rear tire to the curved seat tube? Obviously, the close the tire is
    to the tube, the less wind resistance, but if it's too close, road grit might get caught up...

    What clearance to provide for the tire?
     
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  2. Dianne_1234

    Dianne_1234 Guest

    On Sat, 29 Nov 2003 11:39:07 GMT, "John Crankshaw" <[email protected]> wrote:

    >I'm helping a friend build a Cervelo P3 TT bike.
    >
    >Wondering how close to mount the rear tire to the curved seat tube? Obviously, the close the tire
    >is to the tube, the less wind resistance, but if it's too close, road grit might get caught up...
    >
    >What clearance to provide for the tire?
    >

    IIRC, Cervelo might have been the ones who found closer has less drag.

    I believe UCI regulations at one time called for the thickness of a credit card to pass between.
    Adam somebody was DQ'ed when the official coulnd't get his hotel key card in there.
     
  3. Lennontj

    Lennontj Guest

    From the Cervelo website, Tech Library:

    All Cervelo bikes are UCI Approved for all races. During the development of the P2K and P3 models,
    Cervélo has ensured that these models comply with the new UCI regulations that came into effect on
    January 1, 2000. The main points of the new rules are:

    Frames have to be of a double diamond lay-out Both wheels have to be the same size All tubes have to
    fit within a 80mm wide template, except near the joints where more room is allowed A credit card has
    to fit between the seattube and the tire. Don't jam it through, as the official may not try that
    either. Just play it safe, and if there is any trouble sliding the credit card through, move the
    wheel a millimeter further back. A 3mm gap will enable a credit card to slip through without a
    problem (2.1mm should do it theoretically). The horizontal drop-outs of our TT bikes enable the
    rider to achieve the appropriate gap irrespective of the size of tire used.
     
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