Abstract: A suspension system for a vehicle such as a trailer or tractor wherein ground-engaging wheels on an axle are mounted on a pair of control arms, which in turn are pivotably mounted for vertical swinging motion at one end to frame brackets laterally disposed at opposite sides of the vehicle frame. Spring means are disposed in a load-transmitting relation between another end of the control arm and the vehicle frame. The pivotal connection between the frame bracket and the control arm includes a bolt which passes through an aperture in the control arm and slotted apertures in the frame bracket to provide fore and aft adjustment of the control arm at the pivotal connection. This slotted connection facilitates alignment of the axle relative to the vehicle frame. The bolt is carried in the slotted adjustment apertures by special mounting plates which have means for pivotably supporting the plate on the frame bracket and means for gripping the mounting plates for movement with respect to the frame brackets.