VeloNews Training Center: How should a cyclocross bike fit?

In the first question and answer column in's new Training Center feature, a reader asks whether he should buy a cyclocross bike that is smaller than his road bike.

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Editor’s note: This is the first of a new feature on VeloNews Training Center. Training Center columns and question-and-answer articles are being produced with the Boulder Center for Sports Medicine, one of the nation’s premier sports medicine centers, which works with many top cyclists, including Alberto Contador, Andy Schleck, Fabian Cancellara and Taylor Phinney.

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Q: Dear VeloNews Training Center: I’ve been racing road bikes for about three years now. With cyclocross season coming up, I am thinking of giving it a try and wanted to ask about fit. Some say that a cross bike should typically be slightly smaller than a road bike—I ride a 56cm road bike; does that mean I should be on a 54cm cross bike?

A: Cyclocross is a disciple of cycling that puts great demands on the rider and equipment. Proper bike positioning is crucial in allowing the rider to deliver the necessary power to the pedals and be able to handle the bike in the various terrain.

There are differences between a cyclocross position and a road position. Obviously the different conditions, surfaces, and duration of the race play a factor in the positioning, but also as important are the different shoes, pedals, and saddle choice.

Starting the process is setting up the motor. The mechanics of applying power to the pedals is not different from the road bike to the cyclocross bike! This means that you want to keep your extension to the bottom of the pedal stroke the same. Due to different pedals, shoes, and saddles this dimension may not be the same measurement, but the extension should be the same. Also positioning fore/aft for achieving your maximum tangential power is the same as on your road bike. There are other important variations in using a typical mountain pedal, such as the increased stance width and medial/lateral toggle, or slop, in the cleat.

So if the waist down, or drivetrain, gets positioned the same, where are the differences? The handlebar position is what varies significantly from a road position. The steep grassy descents and rough terrain mean you need less weight on the front end of the bike. Conversely the frequent hard accelerations mean you can’t just shorten the reach to reduce front end weight. The solution is to raise the bars, and not shorten the reach. This allows the body to keep an elongated spine and anteriorly rotated pelvis, which will recruit glutes for power, but slightly shift your mass off the handlebars. Handlebar selection is also important for cyclocross. Shorter drop bars can be very useful in clearing the bars from your arms during out of the saddle accelerations. Some riders prefer the stability and control of the drops position for the majority of the race, and short drop bars allow the rider to maintain this position easier.

In shopping for a cyclocross bike, achieving your ideal position usually does not mean sizing down. Top-tube dimensions should be similar to what you ride on the road. The main difference in a ‘cross frame should be a slightly longer head tube to accommodate a slightly higher handlebar position.

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