| 摘要 |
A payload-carrying motor vehicle comprises a steer axle, at least one drive axle and a tag axle. All of the axles have wheels with tires and air brakes and a tag axle suspension system is 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 against a road surface to aid in supporting the vehicle. An air brake system is adapted to operate the air brakes of all the wheels and a tag axle operating system is 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.
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