Abstract: A trailer body employs hollow and generally rectangular dual wall tubes stacked, interlocked and welded on both sides continuously to form each side of the trailer body. The extrusion walls are of varying thickness to minimize weight and maximize strength and durability.

Abstract: A quarter frame end dump trailer has one or more resilient members placed in its drag link in order to permit the use of an air ride suspension in a tandem axle, spread axle or other multiple axle configuration.

Abstract: A semi-end dump trailer body employs hollow rectangular rubrail along each side of the trailer body with crossmembers of U-shaped configuration with outwardly flared sidewalls welded to the inner vertical wall of the rubrails and to inward, relatively short horizontal extensions of the rubrails and to a floor sheet extending across the body between the inward horizontal extensions of the rubrails whereby to strengthen the body increase its acceptable length, height and load carrying capacity without a significant increase in weight and at little increase in cost.