An air-ride beam-type axle suspension system for tractor-trailers and other heavy-duty wheeled vehicles having a brake chamber of an air brake assembly mounted on the beam, wherein the beam is tapered. Specifically, each beam of the axle suspension system tapers from a narrower width at its end that is pivotally attached to a frame rail of the trailer, to a wider width at its opposite end. The tapered beam provides easier mounting of the suspension system on existing trailer frame rails and incorporation of a reduced-size pivot bushing at the narrower end of the beam, and optimizes the weight of the axle suspension system.