Trail, wheelbase, fork offset

Discussion in 'Cycling Equipment' started by jp_nyc, Feb 26, 2006.

  1. jp_nyc

    jp_nyc Guest

    My current 48cm custom road bike has these dimensions:

    Standover height: 74.4cm
    Top tube: 50.5cm
    Wheelbase: 96.1cm
    Trail: 56.9mm
    Fork offset: 50mm

    I'm looking into buying a used cross bike with these dimensions:

    Standover height: 74.1cm
    Top tube: 51.5cm
    Wheelbase: 97.8cm
    Trail: 64.7mm
    Fork offset: 45mm

    My current road bike takes 700c wheels, while the cross bike is built
    to take MTB 26" wheels. I'm planning on building the cross as a fixed
    gear bike. My concern is with the wheelbase and trail differences. Are
    they significant, and if so, how will I notice them? I'm not able to
    try to the cross out, so I'll have to go on numbers.

    Thanks for your input.
    JP
     
    Tags:


  2. jp_nyc

    jp_nyc Guest

    Edit: switch the standover heights, I got them mixed up. Current road
    bike is 74.1cm, 'cross bike is 74.4cm.
     
  3. Werehatrack

    Werehatrack Guest

    On 26 Feb 2006 14:35:54 -0800, "jp_nyc" <[email protected]> wrote:

    >My current 48cm custom road bike has these dimensions:
    >
    >Standover height: 74.4cm
    >Top tube: 50.5cm
    >Wheelbase: 96.1cm
    >Trail: 56.9mm
    >Fork offset: 50mm
    >
    >I'm looking into buying a used cross bike with these dimensions:
    >
    >Standover height: 74.1cm
    >Top tube: 51.5cm
    >Wheelbase: 97.8cm
    >Trail: 64.7mm
    >Fork offset: 45mm
    >
    >My current road bike takes 700c wheels, while the cross bike is built
    >to take MTB 26" wheels. I'm planning on building the cross as a fixed
    >gear bike. My concern is with the wheelbase and trail differences. Are
    >they significant, and if so, how will I notice them? I'm not able to
    >try to the cross out, so I'll have to go on numbers.


    It looks, on the surface, like a good choice. Increased trail on a
    cross bike or mtb relative to a typical roadie is common. The
    difference in wheelbase isn't enough to matter, but longer tends to be
    better for this type of bike. In particular, a greater distance
    between the vertical centerlines of the rear axle and the seat gives
    better climbing stability in off-road trail situations. Grades that
    are seldom seen on streets are often present on trails.
    --
    Typoes are a feature, not a bug.
    Some gardening required to reply via email.
    Words processed in a facility that contains nuts.
     
  4. RonSonic

    RonSonic Guest

    On 26 Feb 2006 14:35:54 -0800, "jp_nyc" <[email protected]> wrote:

    >My current 48cm custom road bike has these dimensions:
    >
    >Standover height: 74.4cm
    >Top tube: 50.5cm
    >Wheelbase: 96.1cm
    >Trail: 56.9mm
    >Fork offset: 50mm
    >
    >I'm looking into buying a used cross bike with these dimensions:
    >
    >Standover height: 74.1cm
    >Top tube: 51.5cm
    >Wheelbase: 97.8cm
    >Trail: 64.7mm
    >Fork offset: 45mm
    >
    >My current road bike takes 700c wheels, while the cross bike is built
    >to take MTB 26" wheels. I'm planning on building the cross as a fixed
    >gear bike. My concern is with the wheelbase and trail differences. Are
    >they significant, and if so, how will I notice them? I'm not able to
    >try to the cross out, so I'll have to go on numbers.


    Why are you "concerned" about them? The difference in wheelbase and trail, is
    typical for this different application as will be the likely increase in bottom
    bracket height that you don't mention. The difference in wheels will make as
    much difference in feel as anything else.

    The new bike will feel more like a cross bike - stable in horrid conditions but
    still light fast and tossable. Assuming it's a competent build.

    Ron
     
  5. Luke

    Luke Guest

    In article <[email protected]>, RonSonic
    <[email protected]> wrote:

    > On 26 Feb 2006 14:35:54 -0800, "jp_nyc" <[email protected]> wrote:
    >
    > >My current 48cm custom road bike has these dimensions:
    > >
    > >Standover height: 74.4cm
    > >Top tube: 50.5cm
    > >Wheelbase: 96.1cm
    > >Trail: 56.9mm
    > >Fork offset: 50mm
    > >
    > >I'm looking into buying a used cross bike with these dimensions:
    > >
    > >Standover height: 74.1cm
    > >Top tube: 51.5cm
    > >Wheelbase: 97.8cm
    > >Trail: 64.7mm
    > >Fork offset: 45mm
    > >
    > >My current road bike takes 700c wheels, while the cross bike is built
    > >to take MTB 26" wheels. I'm planning on building the cross as a fixed
    > >gear bike. My concern is with the wheelbase and trail differences. Are
    > >they significant, and if so, how will I notice them? I'm not able to
    > >try to the cross out, so I'll have to go on numbers.

    >
    > Why are you "concerned" about them? The difference in wheelbase and trail, is
    > typical for this different application as will be the likely increase in
    > bottom
    > bracket height that you don't mention. The difference in wheels will make as
    > much difference in feel as anything else.
    >
    > The new bike will feel more like a cross bike - stable in horrid conditions
    > but
    > still light fast and tossable. Assuming it's a competent build.
    >


    The only concern I'd have in this case is the possibility of toe touch
    - a real aggravation for fixies. The relevant specs here are BB spindle
    to front axle distance, length of cranks, and tire and shoe size.
    Smaller sized 700c bikes generally exacerbate toe overlap, but the OP's
    custom CX's smaller 26" wheels may provide enough clearance to prevent
    the problem arising.

    Luke
     
Loading...
Loading...