Based on the 90 degree angle formed between the torso and arms, is there a measurement one can take of their torso which will help determine the proper top tube length. (this questions applies to steep angle bikes).
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Re: Fit Question - Top Tube Length [Bri]
[ In reply to ]
I'm sure you can find one online for road bikes, but for tri bikes... probably not. We have a chart that we use that uses torso and arm to produce a projected top tube length. The problem is that there is not as as much margin for error as there is on a road bike because your arms no longer reach out to the handlebars.
As a result we are still trying to refine our system to a formula that can just be applied to your measurements without tweaking. Our current system has been refined over the years on a trial and error basis and is still dependant on some subjective input from the fitter and then fine tuning the fit on the bike.
The goal is to get a formula for fitting that would be like the Gallup Poll: accurate within 2% 19 times out of 20. But 1 in 20 will always be further out because of a very curved back shape, lack of flexibility, etc.
As a result we are still trying to refine our system to a formula that can just be applied to your measurements without tweaking. Our current system has been refined over the years on a trial and error basis and is still dependant on some subjective input from the fitter and then fine tuning the fit on the bike.
The goal is to get a formula for fitting that would be like the Gallup Poll: accurate within 2% 19 times out of 20. But 1 in 20 will always be further out because of a very curved back shape, lack of flexibility, etc.
Re: Fit Question - Top Tube Length [Dan Rishworth]
[ In reply to ]
"The goal is to get a formula for fitting that would be like the Gallup Poll: accurate within 2%"
That would be a very honorable goal, but is it possible with so many variations of arm/torso/leg lengths, as well as flexibility,curvatures, etc as you already mentioned. A formula for approx seat height has been establshed but it seems there is no formula for top tube length, at least not one I'm aware of.
Years ago an old Italian bike mechanic told me to measure correct top tube length by my elbow to finger tips, placing the elbow at the seat tip and your finger tips should be about 1 1/2 inches to your handle bar. Believe it or not, this has worked for me every time, at least with road bikes. Maybe someone could come up with some general "rule of thumb" formula like this for tri bikes as well.
That would be a very honorable goal, but is it possible with so many variations of arm/torso/leg lengths, as well as flexibility,curvatures, etc as you already mentioned. A formula for approx seat height has been establshed but it seems there is no formula for top tube length, at least not one I'm aware of.
Years ago an old Italian bike mechanic told me to measure correct top tube length by my elbow to finger tips, placing the elbow at the seat tip and your finger tips should be about 1 1/2 inches to your handle bar. Believe it or not, this has worked for me every time, at least with road bikes. Maybe someone could come up with some general "rule of thumb" formula like this for tri bikes as well.
If you had numbers for a large population we could come up with something to give a great starting point for fit, like Dan R said
> accurate within 2% 19 times out of 20.
I think that we would need ACCURATE measurements for the following:
inseam, outseam, lower leg, foot, height (floor to top of head), body height (floor to sternum), forearm length (elbow to fist), and arm length (shoulder to fist). We also might want a hip flexibility scale (can you touch your toes) and maybe ankle flexibility scale. Then we need a tri geometry by a reputable fitter (tom, dan, first FIST crew, etc) for a large sample of people, anyone want to start (or have) the data? I'll run some calculations.
A
> accurate within 2% 19 times out of 20.
I think that we would need ACCURATE measurements for the following:
inseam, outseam, lower leg, foot, height (floor to top of head), body height (floor to sternum), forearm length (elbow to fist), and arm length (shoulder to fist). We also might want a hip flexibility scale (can you touch your toes) and maybe ankle flexibility scale. Then we need a tri geometry by a reputable fitter (tom, dan, first FIST crew, etc) for a large sample of people, anyone want to start (or have) the data? I'll run some calculations.
A