Aerodynamics in Cycling

Aerodynamics has become enormously important in bicycle road racing, even more than weight. Bikes are so light these days that it is not unusual to add weights just to get them up to the required minimum weights.

Wind tunnel testing is used extensively both in manufacturing and training. Manufacturers test bikes and components in order to reduce drag. One trend in recent years that I find counter intuitive is wider wheels. Newer rims sometimes have a cross section similar to an airfoil, wide in the front and tapering towards the back, or inside of the wheel. They have also added dimples similar to golf ball dimples.
In general, most tube cross sections are now being stretched out to an airfoil like shape. Each little thing does not change much, but put together they can make a huge impact on the effort the rider has to put out in the end.
A team manager needs to know how to balance many factors such as aerodynamics, weight, cooling, and strength amongst others. As an example for a race with many steep climbs, aerodynamics is less important than weight and cooling for the rider. Maybe a helmet with many vents and high drag is in order so the rider will not over heat. Light but high drag wheels are also ok. On the other hand, it is opposite during a flat time trial, when the rider rides all alone without any drafting behind other riders. In this situation, everything must be low drag, bike, wheels, suit, helmet etc.