Coefficient of Rolling Resistance is the force needed to push (or tow) a wheeled vehicle forward (at constant speed on a level surface, or zero grade, with zero air resistance) per unit force of weight.

Hysteresis is the main cause of energy loss associated with rolling resistance and is attributed to the viscoelastic characteristics of the rubber.

The rubber compound in a bicycle tire exhibits hysteresis. As the tire rotates under the weight of the bike, it experiences repeated cycles of deformation and recovery, and it dissipates the hysteresis energy loss as heat.

The Coefficient of Rolling Resistance is determined by tyre contact patch area, Compound Stickiness, Rider and Bike weight and road surface.

Here are a few sample values:

0.001 bicycle tire on wooden track
0.002 bicycle tire on concrete
0.004 bicycle tire on asphalt road
0.008 bicycle tire on rough paved road