Abstract: A vibration suppressing device for a wheeled construction equipment having a wheeled chassis, a working device operatively supported on the wheeled chassis, and a hydraulic circuit including hydraulic actuators for operating the working device for up-and-down motion. The vibration suppressing device includes an accumulator filled with a pressurized gas for suppressing vibrations, and a mode changeover valve for connecting the accumulator to the load bearing pressure chambers of the hydraulic actuators in a travelling mode in which the wheeled construction equipment operates for running, and for disconnecting the accumulator from the load bearing pressure chambers of the hydraulic actuators in a working mode in which the wheeled construction equipment operates. When the working device is held at a height in the range of zero to a minimum limit height from the road, the vibration suppressing device meets conditions: P.sub.G x V.sub.A.sup.n .ltoreq.P.sub.H x V.sub.F.sup.n and P.sub.G .ltoreq.P.sub.H, where P.