Correct bicycle fit matters to casual riders, weekend warriors, racing cyclists and triathletes alike. While competitive riders take bicycle fit seriously to avoid overuse injury, others can also benefit from bike fitting. Even an inexpensive cruising bicycle gives a more comfortable ride when fitted properly. Specialized tools can check that a bicycle fits you correctly.
Significance
The position of the seat and handlebars, as well as the size and geometry of your bicycle frame, play the main role in bike fit. You can pay a bike shop $50 and up as of 2010 for a professional bike fitting, or it may be free with the purchase of a bike. Triathletes and racers may get professional fittings or use their own tool sets to reassess their fit several times a year.
Types
Tools for bike fitting include an angle-measuring device called a goniometer, held up to the knee, hip, shoulder and elbow, as well as a plumb bob, 24 inches of string and a trainer to serve as a stand during the fitting. An Allen key set allow you to adjust the seat post and handlebars, and a tape measure helps you record component measurements. At the elite level, computerized trainers use bike-fitting software to analyze pedal stroke and produce recommendations for bike fit.
Function
A goniometer features telescoping rods or pivoting clear panels, marked like a ruler, with a central disk providing angle measurements. To use it, set your bike's rear wheel on a trainer and ride for a few minutes to warm up. Stop with one leg at the bottom of a pedal stroke. Have an assistant feel for the bony protuberance on the hip, the greater trochanter. The upper arm of the goniometer points to the greater trochanter, while the axis of the goniometer goes on the knee joint. The lower arm is pointed toward the bony prominence on the outside of the ankle, the lateral malleolus.
The knee should be at an angle between 27 and 37 degrees, as measured by the goniometer, if the saddle is at an optimal height. The trunk angle to the upper arm should be 90 degrees, and the elbows should have a slight 15- to 25-degree bend.
Features
You or your mechanic can adjust seat or handlebar height or position to attain an optimal angle. To test the saddle position, place your foot on the pedal at the 3 o'clock position and drop a plumb line from the front of your kneecap. It should pass through the center of the pedal axle. Move the saddle forward or backward as needed, and recheck the angle of the knee.
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