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Old 02-23-07, 10:23 PM   #1
jim p
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Bike sizing / fit question

I have a french bike which has odd ball size seat post and quill so it is not easy for me to just substitute parts and see how things work. So this is my question. What will going from a 57 cm frame to a 59 cm frame do for me? My seat needs to be moved back by about 4 cm more than it will presently go. My handle bar needs to be raised by about 4 cm minimum. Will a 59 cm frame allow me to do this? I am asking this question because I am planning on getting another bike which will not have the old odd ball size parts so that I can substitute parts as needed. I am thinking that just a larger frame will not correct the fit like I want.
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Old 02-23-07, 11:46 PM   #2
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Frames vary in geometry and how they are sized, so there is not pat answer to your problem. The best course of action is to buy a frame or bike from a shop that can fit you. In fact, your old frame may be irrelevant to your new search.
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Old 02-24-07, 12:47 AM   #3
cyclezen
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hard thing to pin down, what you ask.
however, if you've truly defined your positional needs then inspite of th general irrelevance of ST length, the larger frames usually have have more laid back seat-t angles; which, from your description, is something you're wishing to achieve.
Still, I recommend working with a well qualified fitter to define what you find to be 'best'. If you don;t already have some defined parameters, then getting a starting point is the cornerstone to finding a optimal fit.
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Old 02-24-07, 06:42 AM   #4
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I went through a similar exercise and you can do it yourself if you know the dimensions you're looking for. You'll need to get copies of the geometries of the frames you're interested in and tweak the various adjustments to get the sizes to fit your needs-crank length, stem length, handlebar width, etc. I enjoy doing that kind of thing and I also knew what dimensions I was trying to get to. If you have not been fitted or know exactly the dimensions you want then it is best to go to someone who can help you with that.
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Old 02-24-07, 09:02 AM   #5
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Thanks for the information. I am looking for a comfort fit so that I can go out and ride for 8 hours and not feel like a broken pretzel. Maybe I am wrong but my thinking is that the only way that I can get this type of fit is to do it myself because only I know what parts of my body are complaining. I am thinking about getting out the tape and aluminum tubing and seeing if I can turn my old bike into a test platform long enough to get the dimensions that I need and then trying to find a bike with the dimensions that I need.

Maybe there is a market for a totally adjustable bicycle. Shops could rent the bike and the rider could go out and ride it for a week or two makings adjustments until the rider was satisfied and then these measurements could be applied to the riders own bike. Oh well probably a bad idea. Thanks again for the information. It looks like we are going to have a good day for riding so I am heading out for about a 2 hour spin. Have a great day.
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Old 02-24-07, 09:15 AM   #6
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Quote:
Originally Posted by jim p
Maybe there is a market for a totally adjustable bicycle. Shops could rent the bike and the rider could go out and ride it for a week or two makings adjustments until the rider was satisfied and then these measurements could be applied to the riders own bike.
That's what fit cycles are, JP. Adjustable stationary bikes that can be adjusted until they feel good. Then you apply those numbers to existing frames and see which ones match it.

Do a search for a Serotta fit cycle in your area...
http://www.serotta.com/pages/size.html

Last edited by Big Paulie; 10-04-07 at 09:55 AM.
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Old 02-24-07, 09:17 AM   #7
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My wife is a physical therapist and brought home from work a goniometer - a device that PTs' use to measure body angles like trunk to thigh flexibility, arm to shoulder, etc. especially when folks have orthopedic surgery and there needs to be a baseline for rehab improvement.

So we took the goniometer and measured ALL of the angles and tube lengths, etc. on her present bike. We then printed out geometries for various bike frames off the web to see which ones were closest to her present fit, a comfortable one. She is getting a new bike because the old one is heavy and slow, not because it's not comfortable, and we're looking at doing some credit-card touring this fall.

To be more specific, she wants a steel touring frame to absorb road vibration in shoulders and wrists and to be able to ride all day comfortably. When we measured the Surly Long Haul Trucker in 46 cm & 50 cm sizes, the 46 cm was either exactly matched or within 1 % of all the angles, tube lengths, etc. of her current 02 Giant Boulder step-through bike, telling us that we had a pretty close match and would be able to make finer adjustments once the frame is built up.

A goniometer can be found via the web or if you live in a large enough city, at one of the health-profession equipment stores (our is right across the street from the hospital). A bike shop 'might' have one for sale although if you go get yourself fitted at an LBS, they'll use a goniometer for measurements, too.

To be OT in closing, your present frame may or may not be 'adjustable' for more comfortable fit. When I was in the market for a new bike, I took my MTB in that I'd been riding and we started there for a fitting. The MTB had been adjusted, stem riser added, etc. so it was pretty comfortable. The new bike had a different geometry altogether and was even more comfortable...
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