Abstract: A spring support system for tandem axles that supports the adjacent ends of the springs which support the front and rear tandem axles in the center and automatically adjusts the level of the trailer as load changes by having inflatable air bags that support a movable cross beam relative to the trailer frame. The spring ends are mounted on the movable cross beam. Air bags are inflated at a pressure that is automatically adjusted to be proportional to the load on the trailer. The air bags provide an air cushion support for smoother and more trouble free operation. The movement is guided adequately so that the support is very stable, by automatically adjusting the stiffness of the pneumatic bags which compensate for differing loads.