Vierintäkitkan

Vierintäkitkan, commonly referred to as rolling resistance, is the resistive force that opposes the rolling motion of a wheel or tire on a solid surface. It arises from energy lost during deformation and microscopic sliding at the contact patch. Unlike sliding friction between rigid bodies, rolling resistance persists even when there is no gross slippage because real materials deform under load.

The physical origin of Vierintäkitkan includes viscoelastic hysteresis in tire and road materials, micro-slip at the contact area, adhesion effects, and surface roughness. Temperature, inflation pressure, tire construction, tread pattern, load, vehicle speed, and road surface texture all influence its magnitude. In practice, a higher load, lower inflation, rougher surfaces, or softer materials tend to increase rolling resistance.

Quantitatively, rolling resistance is often modeled as F_r = C_rr × N, where F_r is the rolling resistance force, N is the normal force, and C_rr is the rolling resistance coefficient, a dimensionless value typically between 0.001 and 0.02 for road vehicles, depending on conditions. This coefficient tends to rise with load, worn tires, lower inflation pressure, or rough surfaces.

In vehicle performance and energy efficiency analyses, Vierintäkitkan represents part of the energy required to maintain motion and thus impacts fuel consumption and range in road and rail applications. It can be measured with coast-down tests, on-vehicle tests, or laboratory rolling resistance equipment.

Etymology: Vierintäkitkan comes from Finnish; vierintä means rolling and kitka means friction, with -n as the genitive suffix, yielding “the rolling friction of.”