Abstract: A semi-elliptical spring suspension system is provided in conjunction with a trailing arm and the suspension system may be readily mounted from the longitudinal side members of a vehicle frame. The suspension system semi-elliptical spring comprises a composite spring whose spring rate increases dramatically as the load on the spring is increased and the suspension system is constructed in a manner which isolates the semi-elliptical spring from twisting forces and wind up torque.

Abstract: An upwardly bowed single transverse leaf spring is provided and includes longitudinally spaced central mounting areas between which a longitudinal mid-portion of the spring extends. The spring includes opposite end portions on remote sides of said mounting areas for anchoring relative to vehicle wheel supporting spindle structures and the mounting areas of the spring have mounts stationarily mounted relative thereto but adjustably positionable longitudinally of the spring and the mounts are pivotally mounted from the stationary mounting structures for oscillation about horizontal parallel axes extending transversely of the leaf spring with the pivotal mounting of the mounts from the stationary mounting structures being such that each axis of oscillation of a mount relative to the corresponding stationary mounting structure may be adjusted transversely of the corresponding vehicle.