Frame Geometry for custom build

[roburrito]

I signed up for a frame building class and I've decided to build a steel cross bike. The instructor has a spreadsheet for calculating geometry that uses Paterek's calculations. But you need to enter headtube angle, BB drop, crotch clearance, and inseam.

I've decided to look at some steel cross bikes on the market to get an idea for geometry. So far I've looked at the IF Planet Cross, Gunnar Crosshairs, and Surly Crosscheck. The Crosscheck, as expect, has a relaxed geometry. I was surprised that the Planet Cross seemed surprisingly relaxed as well. So far I'm leaning towards using the Crosshairs' geometry.

Any recommendations on geometry? Any other steel cross bikes I can look at for reference?

Planned riding will be cyclocross races and dirt randonneurs (D2R2).

[Cynikal]

Look at the Lemond Poprad and maybe some more race oriented frames like Cannondale or Raleigh.

[roburrito]

Cannondale only does aluminum frames, I'd imagine there would be some differences in the geometry do to material. I think the Roper is Raleigh's first steel cyclocross. But I think its more commuter oriented. I know Raleigh had a steel randonneur back in the 80s, but I'm not sure how good the geometry would be

[Cynikal]

Raleigh has been in the cross game for about 5 years now with some great race frames like this.


About Cannondale, The geo will remain the same regardless of material but the tube diameters will be different.

[roburrito]

I would think with all the curves and strange shapes that carbon bikes can have that would significantly affect geometry in a way that a steel bike can't emulate. Just look at the top tube of the bike you linked to.

[fietsbob]

There is a copy on the web somewhere of one of the AlAn cross frame set tube length charts.

it was in their sales trifold..

They had a lot more frame dimensional changes than are offered by mass market builders..


More a tourist, I had a 57/57.. managed to find a Pinarello in steel later,

when the 'lugs' of the screwed and glued frame started to show cracks.

[fietsbob]

the seat tube angle is related to femur length..

[Cynikal]

Actually no. While the shapes of the tubes change the appearance and ride characteristics (stiffness and flex) of the bike they do not alter the geometry (handling). Measurements and the angles are measured from the center of the tube and joint. Look at the diagram below



Edit: Man is this new software buggy today.

[Andy_K]

This definitely seems like something worth discussing with the instructor, but I think things like tube angles and chainstay length should be independent of tubing material. The shape of the tubes does have an impact on the stiffness and compliance of the frame. I don't know enough about it to know how that's managed with steel tubing. Personally, I would prioritize handling over stiffness for a CX bike.Back to your original question, a reviewer for CX Magazine really liked the geometry of the All City Nature Boy. I'd also look at Kona and Ridley, though they aren't steel.

[roburrito]

Poprad and all city nature boy were great suggestions, their geometry is very similar. Thanks!