Trailer for a trailer train

The trailer (10) has a support frame (12) with a carriage (16) arranged centrically in a driving direction. The carriage has lateral wheels (18) that are connected with a throttle valve having a hydraulic cylinder for height-adjustment of the frame relative to the chassis. The frame is coupled with a support frame of another trailer by a drawbar (22). The valve has a pump that produces hydraulic pressure in rotation directions of the wheels and includes a rotation drive coupled with the wheels by a gear e.g. friction gear, chain gear and belt gear, where the wheels are scrolled at ground.