On Fit: Procedural Information

This article is the second in a series on bicycle fit. In this article, I will present some tips on fit, stolen directly from the Andy Pruitt book on bicycling, as well as the wise words of Glenn Swan of Swan Cycles, near Cornell. (If you're coming to "Shop Hours" tomorrow, I'll show you these same tricks.)

I'd like to make a few disclaimers, first. No single algorithm can perfectly determine your position on the bicycle the first time through. Your position on your bicycle is the result of a long-term relationship, and a series of tweaks, calibrations, and meditations. Furthermore, these tips make a fairly strong assumption: you have a road bike, and want to go fast. You must be flexible enough to touch your toes after a brief warm-up, or else a few things change.

Your fit must take your body into account. If you have a curved spine, severe pronation, legs of different lengths, or any known medical conditions, you need to address these, not ignore them.

When I fit people, I think about the five points of contact to the bicycle: shoes, saddle, and hands. I work from the bottom up. I use a trainer to secure the bike, and a plumb bob and goniometer to measure angle and position. I have a centimeter measuring tape, pen, and paper handy.

The centerline of the cleats should be just below the balls of the feet. I ask people to put their cycling shoes on, and find the bumps on the inside and outside of the front of the foot. This tells me where the ball of the foot is. I adjust the cleats to be centered on a line between these two points, and adjust rotation so the rider's foot is in a good neutral position.

Saddle height is the tricky one. I start with the LeMond formula, with the saddle height at 0.883 times the rider's inseam from crotch to floor. I then ask the rider to ride for 5 minutes, then make changes and observe. When I'm done, the rider's leg is extended to 25 degrees at the bottom of the stroke (I use the goniometer here). With cranks horizontal, the front of the forward knee should be right over the end of the crankarm (I use the plumb bob here).

Handlebar width is very straightforward: the center to center dimension of the bars should be the same as the distance between the bony bumps on the rider's shoulders, where the arm attaches to the collarbone.

Reach is somewhat tricky as well. One useful starting point is to have the rider place their elbow at the tip of the saddle, and adjust stem length so the bars are within 2-3cm of the tip of their index finger. The rider should have knee clearance in all positions. The rider should not be supporting a large percentage of their body weight on their hands; I check this by putting my hands under theirs. When adjusting height, I want the rider's body to be at a 40-45 degree angle to the ground; this varies depending on the experience, agressiveness, and flexibility of the rider.

Aero bars offer a slightly different issue. With those, I want the rider to be a little more forward on the saddle. The upper arm should be about parallel to the front fork, and the forearm should be at just about a 90-100 degree angle to the upper arm. The pads should be under the "meat" of the forearm, and supporting a fair amount of the rider's weight.

Many people seem to have a poor view of this elementary fit principle. I respond with the disclaimer: this offers a starting position, nothing more and nothing less. A proper fit is the result of time and effort, more than I can do in an hour at my current level of expertise.