Compression and Rebound Damping
Compression damping and rebound damping are damper forces that oppose suspension motion in the two directions of stroke.
Compression damping
Compression, or bump, damping acts while the damper shortens. It helps control wheel and body motion during road impacts, braking, cornering, and heave, but excessive force can transmit harshness or prevent the wheel from moving quickly enough over an input.
Rebound damping
Rebound damping acts while the damper extends. It controls the release of spring energy and helps limit repeated body oscillation. Too much rebound force can keep the suspension compressed over successive bumps, while too little can allow persistent movement.
Force depends on speed and position
Damper force is normally described against shaft velocity, not vehicle speed. Low- and high-speed damping refer to damper movement speed. Valves, bypasses, temperature, fluid condition, gas pressure, position-sensitive features, and electronic control can change the curve.
Compression and rebound settings are not direct measures of spring stiffness or wheel force because motion ratio and installation angle matter.
For damper construction and force–velocity behavior, see Suspension Dampers. For how damper motion relates to wheel and body motion, see Suspension Kinematics and Vehicle Dynamics.