8 Speed and Power Models

Cycling performance can be modeled and predicted fairly easily once the road forces are understood. Road loads such as aerodynamic drag, rolling resistance, and hill climbing resist the rider’s efforts. If the rider is generating more power at the cranks than the total resistive power, the vehicle will speed up. Conversely, if she is generating less power, the vehicle will slow down. Performance models relate the vehicle speed and ride conditions to the power required of the rider. They can predict performance for competitive events and the potential for success in record-breaking efforts. They are also useful for determining if a vehicle is “fast” or “easy to pedal.” In this case, “fast” is taken to mean that under typical operating conditions and with an average rider generating average power, the vehicle is faster than an average or typical vehicle. “Easy to pedal” may mean the same thing, but often the implication is that at average speeds the power required is less than that for an average vehicle.