A solid-tire-and-hub assembly is provided. The assembly includes a solid tire defining a pair of opposed, spaced side surfaces and a pair of opposed, spaced facial surfaces extending between the side surfaces such that the solid tire defines a substantially trapezoidal transverse cross-section. The solid tire is disposed about a partially hollow hub, which defines a substantially “I” transverse cross-section substantially aligned with the cross-section of the solid tire, an axial aperture configured to receive a drive shaft, and a plurality of holes defined about the aperture. A power-drive unit is also provided. The unit includes a housing, a drive shaft, and at least one of the solid-tire-and-hub assembly connected to the housing.