Abstract: A rotary axle and hub assembly is provided for vehicles having an onboard, automated tire inflation system. The assembly includes a rotary air connection assembly threadably mounted on the hubcap. The rotary air connection can be readily disassembled to allow rotary seal replacement. The rotary air connection is connected to an air conduit that is flexible, coaxially extendable through, and longitudinally and laterally movable in the hubcap and axle, allowing movement and misalignment between the rotating and stationary parts of the axle and hub assembly. The flexible air conduit enters the axle beam via a bulkhead fitting which allows movement of the air conduit in and out of the axle beam, thereby allowing the rotary air connection to be mounted and dismounted from the hubcap. The bulkhead includes a pressure relief valve to allow excess air pressure in the axle and hub areas to be vented to the atmosphere.