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bike fit(6 posts)

bike fitjpsendero06
Oct 25, 2002 5:26 PM
I've been a mountain bike racer for a few years and I'm interested in getting into road racing. I want to know how to determine fit on road bikes. I'm a little over 6'1". How important is proper fit? What can I do to insure that i get the right fit when i buy a bike?
re: bike fitAFrizzledFry
Oct 25, 2002 6:36 PM
fit is extremely important. you will not enjoy your riding on the road if you don't have the proper fit. the best way to find out is probably to go to your LBS and get some kind of idea what fits- a 54 cm bike sure as hell won't at your height. alot of shops offer fit kits and whatnot. i'd seriously consider doing something like that. if you dont get the right fit, you're gonna be kicking yourself after a few months of riding.
It's really importantKerry
Oct 26, 2002 10:52 AM

For adjusting the fit of the bike, there are roughly five starting points:

1. Seat height (top of saddle to center of pedal axle) at 108-110% of inseam.
2. Saddle parallel to ground.
3. Saddle fore/aft adjusted so that a plumb bob from the bony protrusion just below the kneecap passes through the pedal axle when the cranks are horizontal. This is known as KOPS (Knee Over Pedal Spindle)
4. Front hub axle obscured by the handlebars when riding in your "regular" position (drops, hoods, or tops).
5. Top of handlebars 1 to 4.5+ inches below the top of the saddle depending on your flexibility and size.

These are all starting points for "average" proportioned people, and many folks like to move away from these starting points as they learn what makes them more comfortable, powerful, or efficient. You want to get the fit of the frame as close as you can, then do minor adjustments with the stem, seat post, saddle position, etc.
try these sites.....C-40
Oct 26, 2002 10:53 AM
also tryspc15
Oct 26, 2002 11:19 AM

I am a bit over 6'1" myself and this site helped me greatly in fitting a recently purchased CT1 to perfection.

I really paid close attention to the top tube length and whether or not the frame measured center to center or center to top(very important)....Know your center of BB to seat height as well as the optimal distance from seat to stem; the wrench science site will calculate this for you.

I found it interesting the different geometries of manufacturers, fwiw.
only ball park numbers....C-40
Oct 26, 2002 12:33 PM
The Wrench Science fit program has a major ommission. It has no way to take into account leg proportioning which is a major factor in determining the proper seat tube angle. It also has no input for preferred KOP position. Without this type of information, it can't make a recommendation for seat tube angle. Selecting a 72 degree STA over a 74 degree STA can make 2-3cm difference in the overall reach, if the knee is positioned in the same place in relation to the bottom bracket.

I plugged in my dimensions and found that is was correct on the vertical frame size (55cm), but suggested a 68cm reach. This would mean a 55cm top tube and a 130mm stem. I have a short torso. I still use a 110mm stem, which produces a reach that most would consider quite long. I have substantial knee to elbow clearance riding in the drops. Most riders my size would choose a 90 or 100mm stem.

The program must make some sort of assumption regarding femur length, seat tube angle and KOP position to derive a total reach. Apparently the assumptions differ a lot from what I use.