rolweerstand

Rolweerstand is the resistive force that must be overcome to roll a wheel or wheel-like object over a surface. It is caused mainly by energy losses due to deformation of the tire and the surface, internal friction in the tire itself, and minor slippage or hysteresis at the contact patch, as well as bearing and suspension losses. It is not a simple static friction force but a combination of several loss mechanisms that act during rolling.

In engineering practice, rolling resistance is often summarized with the rolling resistance coefficient (Crr), defined by Frr = Crr × N, where Frr is the rolling resistance force and N is the normal load (the weight component perpendicular to the surface). Crr values are usually a few thousandths, but vary with tire type, inflation, load, surface texture, speed, and temperature. Typical ranges are roughly: road vehicles 0.005–0.015, bicycles 0.002–0.01, and railways with well-maintained wheel-rail contact about 0.001–0.003. Values tend to decrease with higher inflation and smoother surfaces, and increase with softer or uneven surfaces and higher speeds up to a point.

Factors influencing rolweerstand include tire construction, tire pressure, load distribution, surface roughness, temperature, speed, and lubrication at contact interfaces (for railways and some wheel-bearing systems). Because rolling resistance directly affects energy consumption and, for electric vehicles, driving range, efforts to reduce Crr—through better tires, proper inflation, and smoother surfaces—are common efficiency measures. Rolling resistance is distinct from aerodynamic drag, though both contribute to total resistance at higher speeds. Measurements are obtained via coast-down tests, dynamometer tests, or wheel-on-plate setups used in automotive and rail industries.