Abstract: A rear frame of a trailer has an elongated horizontal sill having a closed cross-section which is rigid in bending and in torsion. The elongated horizontal sill is formed of a fantail and a base plate attached to an underside of the fantail. The base plate has front and rear sections that are not notched as notching of the sill can weaken it. The front section is horizontal and the rear section is angled upwardly relative to the horizontal front section at a predetermined angle of approximately 22 degrees. The angling of the base plate provides a specialized geometry for accommodating a tuck-under lift gate. The sill also has minimal vertical dimensions to aid in the non-interference with legs of the tuck-under lift gate.

Abstract: A vehicle suspension system is provided that includes a frame and pair of laterally spaced apart upper control arms pivotally supported by the frame at pivotal connections. A knuckle is connected to each of the upper control arms. A leaf spring is connected to the lower portion of the knuckles at pivotal connections and serves as the lower control arms. The upper control arms extend away from the knuckles, and air springs are arranged between the upper control arms and the frame. A pressurized air system is connected to the air springs to control the air springs for providing desired ride characteristics.