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Custom frame geometry ???'s(5 posts)

Custom frame geometry ???'smikebikr
Feb 19, 2002 5:31 AM
Here is the proposed geometry on my new Columbus Foco steel bike. Any comments, suggestions etc. What kind of ride can I expect from this bike? I'm a recreational racer who is placing comfort over speed at this point. I beleive what the builder is telling me, I just twant a 2nd/3rd ...opinion.

The drawing reflects a road frame with a slightly sloping top tube with an effective length of 56.6cm. This length is designed for use with a 120mm long, -10 degree rise Magic stem and Magic bar. The seattube tube length is 56.22cm, center to top, at a 73.2 degree angle designed for a straight seatpost. Headtube length is 167mm and with the bar/stem combo and a 1cm spacer gives a saddle/bar delta of 57.6mm IF you raise your saddle to 757mm from your current 750mm (you're riding your saddle a little low, it's that MTB'r in you). I can increase headtube length to decrease that measurement but I think it's a good dimension for now. Front end geometry is a 73-degree headtube angle designed to work with a Reynolds Ouzo Comp with 43mm of offset giving 57.5mm of trail (an excellent figure for all around riding). Bottom bracket drop is a stable 70mm and chainstays are likewise a stable 415mm long. Overall wheelbase is right at a meter.
I think this is an excellent combination for you and will meet your needs for all around riding, it is not super agressive, but it will be more comfortable and won't slow you down regardless of climbs or descents or sprints.
Know your builderboneman
Feb 19, 2002 6:05 AM
You're paying for your builder's experience. If the builder has a good reputation and you feel that the fitting/measuring process was satisfactory, the results should be fine. Judging from the detail, you've clearly communicated your specific needs and he/she seems to have taken notice.

Just a thought but you might want to have the frame built with a slightly taller head tube so you can eliminate the spacer. If you're not really sure, don't do so as cutting the top tube, while possible in a non-lugged frame, is not why you're going custom. Personally, I would have BB drop of 75mm but that's personal taste and again why you go custom.

I've had three custom steel frames made, two in the past 4 months, and found that the one in which I was fitted on a fitting jig to fit the best. As for Foco, I think you'll like the tubeset. I strayed away to Ti for a few years but my new road frame, Deda SAT14.5 (the other option was Foco), is only slightly heavier Ti, sufficiently stiff and yet has a great ride quality.

Good luck. Communicate your needs clearly and trust your builder.
might help to know YOUR geometrynm
Feb 19, 2002 6:06 AM
re: Custom frame geometry ???'skoala
Feb 19, 2002 6:16 AM
I cant speak about your triangle dimensions without knowing all your measurements but one observation is that you must have a relatively long upper body to have a top tube that long relative to the seat tube, especially since a 120mm stem is specified. I can speak to the ride of a well made foco bike. I have a 55cm c-c bike with a slightly tighter wheelbase and similar angles. The ride is clearly superior to my old nivachrome colnago or cannondale. The frame is very stiff yet soaks up road irregularities with aplomb. Perhaps the only place ti has a ride advantage is over larger bumps or potholes. If the fit is right you will love this ride.
re: Custom frame geometry ???'sbrider
Feb 19, 2002 9:31 AM
The ONLY things a good builder needs to know is (1) the cockpit dimensions that you want, and (2) the ride characteristics you want. He (or she) will know what the frame geometry should be from that. The challenge is the (relatively inexperienced) rider conveying the desired ride characteristics.