Abstract: A trailer includes a frame having a plurality of bell cranks pivoted to the frame. A plurality of suspension units are pivotally connected to the frame to permit independent directional displacement of each suspended unit with respect to the frame. A directing means is provided for directing the trailer in the intended direction, the directing means including at least one, and preferably a pair, of master hydraulic cylinders. A plurality of hydraulic slave cylinders connected to the master cylinders are connected to the master cylinders and to the bell cranks for pivoting the bell cranks with respect to the frame in response to any angular displacement of the directing means, thereby causing the suspension units to pivot such as their axles are directed toward a common center defining the center of the curve through which the trailer is directed.