The towed machine (1), having at least one axle with wheels, incorporates a system (4) that positions the wheels to compensate for slip on sloping ground. The system can be one in which the angle of the axle is adjusted by a power cylinder (7) or other mechanical means. It can also be in the form of vertical pivots for the wheel mountings and a transmission mechanism. Alternatively it can include a slope detector (3) and a false chassis articulated to the machine's main chassis.
