The wind plays a big part in the forces affecting a bicycle and its rider. The air flow over a rider and their bicycle is far from smooth. Wind resistance, sometimes called drag, is caused by the atmospheric flow around the rider, wheels, and frame and can produce a relatively large frictional force especially at higher speeds.

At higher speeds this resistive force can be approximated by:

R=1/2DρAv²

Where ρ is the density of air, A is the cross-sectional area of the rider&bike, v is the velocity, and D is

the drag coefficient. There are basically only two ways to reduce drag. The first method is to reduce the overall cross-sectional area. The can be accomplished by using a bicycle that is specifically designed to put the rider into a more aerodynamical position, as seen in figure 2.

Reduction of the drag coefficient is also an important factor in decreasing the resistance. By wearing tighter fitting clothes and using bikes that are streamlined we are able to reduce the drag coefficient significantly.

The study of improved aerodynamics is imperative to any competitive road or track cyclist. Reduction of cross-sectional area can be seen in the image on the right. Notice the skin tight suit, smoothly shaped frame and wheels, as well as a more aerodynamic helmet. Whereas the rider on the left is more of a recreational cyclist and probably would not be seen dead in cycling shorts and a dorky helmet.

Figure 1

Figure2