This posting is the first in a series on the topic of bicycle fit. I'll briefly discuss positioning on a road bike, and what you should look for when sizing yourself on a bicycle. The things I suggest are largely based on Pruitt, as well as tips I've picked up over the years. I'll discuss fit philosophy here, and leave the technical details for future postings.
Regarding fit, you can think of a bicycle as a sort of external skeleton that contacts your body in exactly five places: left and right feet, left and right hands, and crotch. It is very important how these five landmarks are positioned with respect to one another, and how much variation you have in these positions.
Fit is far and away the most individual factor of your bicycle. It directly affects your comfort, your power output, and how well you can avoid injury. If you are short, have a long torso, are not particularly flexible, or have legs of different lengths, your bicycle has better reflect this. My girlfriend Jane and I are proportioned very differently: though there is a height difference of about four inches between us, her torso is longer than mine, and my legs are much longer than hers. Our bicycles reflect this: mine is taller, hers is longer.
There are all sorts of formulas, algorithms, rules, and lore that are connected with fit. No matter what, there is a common thread to all of the methods: you must be comfortable. You must be meticulous and relentless. You must always ask yourself, "Am I in pain, and am I doing anything to address this pain?" If any part of you is sore, numb, or tender after a ride, there is something we must do to correct your position on the bicycle.
I find it helpful to think of the bicycle as part of a system (some would call this a holistic, Zen, or European approach). My body, the bicycle, and the clothing and components on body and bicycle must all work together to propel me down the road at high speed and efficiency. I also find it helpful to scrutinize each aspect of fit in its own right (some would call this an American approach, and do so grudgingly).
In the coming days, I will post more procedural information on the topic of bicycle fit. Stay tuned!