Small Bikes - Handling

Discussion in 'Cycling Equipment' started by DaveH, May 3, 2004.

  1. DaveH

    DaveH Guest

    I am about to buy a road bike for my wife. She will need a bike in a
    frame size about 52cm. However I note that manufacturers now seem to
    be using one fork rake for all their bike sizes, with head angles
    varying from 71 to 74 degrees, eg Giant (XS - 71 deg and 45mm rake),
    Fuji (52cm, 72 deg and 43mm rake) Colnago (52cm 71deg and 43mm). This
    leads to high trail figures of 65mm to 69mm. The ideal trail is
    (apparently) around 56mm.

    Such trail must really negatively affect the handling of these bikes,
    making it slow and with a self centering action.

    There must be riders out there who are using these bikes. How do you
    find the handling? What are you thoughts?
     
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  2. Harris

    Harris Guest

    DaveH <davidnharton@yahoo.co.nz> wrote:
    > I am about to buy a road bike for my wife. She will need a bike in a
    > frame size about 52cm. However I note that manufacturers now seem to
    > be using one fork rake for all their bike sizes, with head angles
    > varying from 71 to 74 degrees, eg Giant (XS - 71 deg and 45mm rake),
    > Fuji (52cm, 72 deg and 43mm rake) Colnago (52cm 71deg and 43mm). This
    > leads to high trail figures of 65mm to 69mm. The ideal trail is
    > (apparently) around 56mm.


    > Such trail must really negatively affect the handling of these bikes,
    > making it slow and with a self centering action.


    Doesn't the Giant use 650c wheels on the XS size? That would reduce trail
    a bit compared to a 700c wheel.

    Obviously toe overlap is an issue with small frames. But I don't see why
    they wouldn't use more offset (aka "rake") to bring the trail number into
    line when using slack head angles. More offset would also improve toe
    clearance.

    Art Harris
     
  3. Robert Brown

    Robert Brown Guest

    DaveH wrote:

    > I am about to buy a road bike for my wife. She will need a bike in a
    > frame size about 52cm. However I note that manufacturers now seem to
    > be using one fork rake for all their bike sizes, with head angles
    > varying from 71 to 74 degrees, eg Giant (XS - 71 deg and 45mm rake),
    > Fuji (52cm, 72 deg and 43mm rake) Colnago (52cm 71deg and 43mm). This
    > leads to high trail figures of 65mm to 69mm. The ideal trail is
    > (apparently) around 56mm.
    >
    > Such trail must really negatively affect the handling of these bikes,
    > making it slow and with a self centering action.
    >
    > There must be riders out there who are using these bikes. How do you
    > find the handling? What are you thoughts?


    Mine - Colnago so-called 54 cm frame (actually 52,5 cm from centre of
    bottom bracket to top of top tube, so this particular frame might be good
    fit for your wife but I'm going to ride this one until I break it ;-).
    Geometry is 74 deg seat tube, 71,5 deg head tube. Fork blades are
    straight but are angled from the steerer to cause effective rake.

    I find the handling very stable, almost lazy in feel. By this, I mean the
    *opposite* of nervous or twitchy. Very nice bike for long distance
    competitions or credit card touring. Relaxing.

    I have had quite twitchy frames in earlier years (e.g. a custom 73,5 deg
    seat and 73,5 head, with short-rake forks, or an Alan 75 deg seat and 74
    head, similar short forks). Both were much fun in the crits I rode but
    slightly irritating on longer rides (always spent some energy making sure
    I rode in a straight line, for some reason).

    Unfortunately I cannot help you on the evaluation of trail - I have not
    yet read up on it to understand the correlation with handling
    characteristics.

    /Robert
     
  4. "DaveH" <davidnharton@yahoo.co.nz> wrote in message
    news:fc6c9e34.0405030311.48ecf87@posting.google.com...
    > I am about to buy a road bike for my wife. She will need a bike in a
    > frame size about 52cm. However I note that manufacturers now seem to
    > be using one fork rake for all their bike sizes, with head angles
    > varying from 71 to 74 degrees, eg Giant (XS - 71 deg and 45mm rake),
    > Fuji (52cm, 72 deg and 43mm rake) Colnago (52cm 71deg and 43mm). This
    > leads to high trail figures of 65mm to 69mm. The ideal trail is
    > (apparently) around 56mm.
    >
    > Such trail must really negatively affect the handling of these bikes,
    > making it slow and with a self centering action.


    If I calculate it correctly, the Bianchi Brava 52cm, with fork rake of 50mm
    and head angle of 72 degrees, has a trail of 61. Still a bit high, but
    better than on the bikes you note.

    The way to reduce this is to go to 650mm wheels, but these are only used on
    very small frames.

    The problem is that the manufacturers don't want to make a bunch of
    different forks.
     
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