Abstract: A body of foam rubber overlies a generally cylindrical rim of the wheel of the assembly. A tread rubber body has a central section that overlies the outer surface of the tread rubber body. Side sections of the tread rubber body extend angularly from its central section and overlie opposite sides of the foam rubber body. The foam rubber body is bonded to the rim of the wheel assembly. A central section of the tread rubber body is boned to the outer surface of the foam rubber body. Opposite side sections of the tread rubber body are bonded to opposite sides of the foam rubber body, and may also be bonded to opposite edge portions of the wheel rim. The side sections of the tread rubber body reduce the possibility of foam rubber being ejected from the sides of the foam rubber body, and also reduce outward expansion of the bodies due to centrifugal force.