Variable-geometry suspension apparatus (600; 800) for a vehicle, the apparatus comprising a resiliently compressible member, an actuator, a control system and support structure (610, 620), wherein: the resiliently compressible member is mounted to the support structure (610, 620) for compression under the weight of a mass suspendable by the apparatus (600; 800); the compressible member is mounted with at least one end of the compressible member displaceable in a displacement direction having a component perpendicular to the direction of compression, so that such displacement varies the geometry of the suspension apparatus and thereby varies the compression of the compressible member; and the actuator is arranged for displacing the one end of the compressible member in the displacement direction to vary the geometry and thereby vary the compression; and the control system having means for carrying out the steps of: receiving at least one signal indicative of one or more of the wheel bounce and yaw, pitch, roll and bounce of a vehicle to which the apparatus is fitted; and applying a transfer function to the at least one signal to generate a measure of the desired displacement of the at least one end of the resiliently compressible member, wherein the transfer function comprises: i) a displacement saturation function to limit the displacement between limits; and/or ii) a velocity saturation function to limit the rate of change of displacement between limits. the resiliently compressible member is mounted to the support structure (610, 620) for compression under the weight of a mass suspendable by the apparatus (600; 800); the compressible member is mounted with at least one end of the compressible member displaceable in a displacement direction having a component perpendicular to the direction of compression, so that such displacement varies the geometry of the suspension apparatus and thereby varies the compression of the compressible member; and the actuator is arranged for displacing the one end of the compressible member in the displacement direction to vary the geometry and thereby vary the compression; and the control system having means for carrying out the steps of: receiving at least one signal indicative of one or more of the wheel bounce and yaw, pitch, roll and bounce of a vehicle to which the apparatus is fitted; and applying a transfer function to the at least one signal to generate a measure of the desired displacement of the at least one end of the resiliently compressible member, wherein the transfer function comprises: i) a displacement saturation function to limit the displacement between limits; and/or ii) a velocity saturation function to limit the rate of change of displacement between limits. receiving at least one signal indicative of one or more of the wheel bounce and yaw, pitch, roll and bounce of a vehicle to which the apparatus is fitted; and applying a transfer function to the at least one signal to generate a measure of the desired displacement of the at least one end of the resiliently compressible member, wherein the transfer function comprises: i) a displacement saturation function to limit the displacement between limits; and/or ii) a velocity saturation function to limit the rate of change of displacement between limits. i) a displacement saturation function to limit the displacement between limits; and/or ii) a velocity saturation function to limit the rate of change of displacement between limits.