An axle/suspension system for the trailer of a tractor-trailer vehicle combination includes a device for leveling the trailer floor. A selected one of a pair of suspension assemblies of the system is pivotally attached to a vehicle frame bracket or hanger having vertically-oriented oval sidewall openings and vertically-spaced horizontally extending eccentric collar guide tabs. The frame hanger, upon a certain manual rotational adjustment of an eccentric alignment collar with a breaker bar, causes a bolt which pivotally attaches the suspension assembly beam to the hanger to be vertically adjusted, which in turn causes vertical adjustment of the beam and the axle attached to the beam, resulting in the raising or lowering of a sidewardly leaning trailer floor to a generally horizontally level position.