Trail, wheelbase, fork offset

[jp_nyc]

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

 

[jp_nyc]

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

 

[Werehatrack]

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.

 

[RonSonic]

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

 

[Luke]

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