Wheel Rate
Wheel rate is the change in vertical force at a wheel for a corresponding change in wheel displacement.
Different from spring rate
If a spring acts through a control arm or linkage, its deflection differs from wheel travel. The motion ratio converts spring rate into a contribution to wheel rate, commonly with a squared ratio when a consistent displacement-ratio convention is used.
The effective rate at the wheel can also include tire stiffness, bushings, bump stops, anti-roll bars, multiple springs, and geometric changes through travel. A quoted wheel rate must therefore state whether it covers one spring path, the suspension alone, or the complete vertical system.
Wheel rate helps determine ride frequencies and body response together with sprung mass, while tire and unsprung mass dynamics remain separate parts of the system.
For spring mechanisms, see Suspension Springs. For motion ratio and wheel geometry, see Suspension Kinematics and Vehicle Dynamics.