Patent ID: 7775533

Claim:
A payload-carrying motor vehicle comprising a steer axle, at least one drive axle, a tag axle, all of said axles having wheels with tires and air brakes, a tag axle suspension system adapted to suspend the tag axle in an active condition wherein the tag axle is pivotal about a first axis parallel to the other axles and also about a second axis located equidistant from the tag axle wheels and laying in a plane at right angles to the first axis and wherein the tag axle is forced to urge the tag axle tires to bear against a road surface and accept a predetermined load, an air brake system adapted to operate the air brakes of all the wheels, and a tag axle operating system adapted to establish the tag axle in the active condition while enabling operation of the air brakes of the tag axle wheels and to disable operation of the air brakes of the tag axle wheels when the tag axle pivots about the second axis and reaches a predetermined tilt angle in maintaining contact of the tag axle tires with a road surface.