Abstract: A steerable machinery trailer (1) has a chassis (2, 33, 35, 36) intermediate a pivotal towing attachment (26, 29, 30, 46) and trailer wheels (3) proximate a rear portion of the chassis. The trailer wheels have pivotal attachment to the trailer and are pivotal for steering with a steering shaft (4) that is length-controllable intermediate rigid positioning on the chassis and a steering arm (6) attached to a steering rod (7) that is connected to a pivotal attachment of the trailer wheels to the chassis. Separately and optionally from being pivotal on the pivotal towing attachment by wheel-following of the trailer wheels, the chassis is pivotal on the pivotal towing attachment with a positioning shaft (8) that is length controllable intermediate rigid positioning on the chassis and a rigid lateral attachment (5, 9) to the towing vehicle. Length changes of the steering shaft steer the trailer wheels to guide the rear portion of the trailer from-side-to-side for selective turn-positioning of the trailer wheels.