Rollwiderstandskoeffizient

Rollwiderstand, commonly translated as rolling resistance, is the resistive force that opposes the motion of a rolling tire, wheel, or similar element as it stays in contact with a surface. It is a primary source of energy loss in road transport and directly affects fuel consumption, vehicle range, and overall efficiency.

The mechanism behind rolling resistance is mainly the viscoelastic deformation of the tire and the contact patch with the road. As the tire deforms under load and then returns to its shape, energy is dissipated as heat due to hysteresis in the rubber and the tire structure. Other contributions come from deformation of the wheel, bearings, and the surface microstructure. The resistive force is often expressed as F_rr = C_rr · N, where C_rr is the rolling resistance coefficient and N is the normal load. The corresponding power loss at speed v is P = F_rr · v = C_rr · m·g · v.

Several factors influence rolling resistance. Inflation pressure, load, and temperature affect the tire’s stiffness and deformation; tire construction, tread design, and rubber compounds influence hysteresis losses; road surface, speed, and environmental conditions also play roles. Proper tire inflation and appropriate tire choice can reduce rolling resistance, though trade-offs with grip, handling, and wear must be considered.

Typical values for C_rr vary by application. Passenger car tires on asphalt typically range around 0.006 to 0.012 for low rolling resistance designs, higher for conventional tires. Bicycle tires may range from about 0.002 to 0.006, while steel-wheel railway applications can be around 0.001 to 0.002. Rolling resistance is distinct from aerodynamic drag and drivetrain losses, but together they determine the total energy required for motion.