The rider's frontal area is evaluated approximately from the rider's body height and weight, and a parameter which depends on the selected kind of bicycle (see FAQ). These assumptions yield good matches with frontal area measurements, and with measurements done with SRM Power Measuring cranks. Inside the fully streamlined bicycles, of course, the rider's frontal area is assumed to have no influence.



The rolling frictions of the front and rear wheel tires each are taken into account separately.



The calculation also regards the following influences:

Load distribution front/rear wheel. At wider tire tends to generate less rolling friction but more air resistance (not true with the streamliners White Hawk and Quest whose fairings enclose the wheels almost entirely). A thicker tire wall (touring tire) tends to generate higher rolling friction. Tire thread induces air vortices and thus speed-dependent additional resistance. The front wheel has more share in the air drag than the rear wheel. Smaller front wheels of recumbents generate more rolling friction but less air resistance. The air drag share of the bicycles themselves is taken into account too.



At low speeds a wider tire (less rolling friction) may be advantageous while, with higher velocity, a narrower one (less air resistance) increasingly gets the upper hand.



The applied rolling resistances refer to asphalt road pavement. On a smooth velodrome surface, rolling resistances may be essentially lower. Consider this also for the values that this calculator delivers for the Superman Position.



Most of the data and assumptions used for the calculator are based on (and match well with) frontal area measurements, and, first of all, measurements done with SRM Power Measuring cranks.

