Suspension system for controlling switching attenuation forces at front wheels and rear wheels. A road surface sensor is provided under a front side of a vehicle body and moves so as to displace a road surface detecting position forwardly of the vehicle body. At the time of an intermediate speed, the road surface sensor itself is displaced forwardly of the vehicle body by an angular displacement apparatus. At the time of a high speed, the road surface sensor itself is further angularly displaced forwardly by an angle variable apparatus in a maximum displacing state to move the road surface detecting position forwardly. A delay time is calculated as required, and an attenuation force switching signal is outputted to the front and rear wheel suspensions, and a timing for at least the front wheel to arrive at the road surface detecting position is always brought substantially into coincidence with the timing for switching the attenuation force of the front wheel suspension by considering the delay time of the control system. Thus, the road surface sensor is suitably displaced and angularly displaced, thereby to optimize detection of a road surface and always switch suspension characteristics relative to a delay of a whole control system at an optimum timing in a whole travel area.