A wheel assembly provides an expanded air-pressurization chamber to increase the load capacity of the mounted tire. The wheel assembly includes an axle shaft, including flange plates mounted at opposite ends of the shaft and a mounting disc attached to each flange plate. There is an annular-shaped locking ring attached to each mounting disc. A cylindrical insert assembly is mounted between the pair of locking rings. A central section is defined in the tubular body extending between a pair of annular flange wall portions and includes an array of holes. The tire bead at each inner edge of a tire is located within the annular bead-receiving channels formed between the locking ring and insert assembly. A dual air-pressurization chamber is formed, one radially outward and the other radially inward of the tubular body of the insert assembly.