A steerable lift axle/suspension system for a heavy-duty vehicle such as a semi-trailer or a straight truck, includes a pair of steering dampers and a backup lock. The steering dampers minimize shimmy of the steerable wheels during over-the-road operation of the vehicle, and straighten the wheels on such steerable axle/suspension systems having a lift feature when the system is raised. The backup lock secures the wheels in a straightened position when such liftable systems are raised and the vehicle is backing up, to minimize vehicle handling problems. The steering dampers and backup lock are mounted at a location off the axle tube of the axle and on the axle/suspension system beams, to eliminate stress on the axle that would otherwise be caused by welded attachment of such components to the axle tube, thereby enabling use of a less robust, more lightweight axle tube.