A wheel/tire stabilizing assembly that can be removably mountable to a rear (or other) wall of a pickup truck bed is presented herein. The assembly can be used to facilitate the hauling of a wheeled vehicle (e.g., a motorcycle or bicycle) in the pickup truck bed, for example, by engaging or receiving one or more wheels/tires for stabilization. The assembly includes a wheel bracket and a mounting clamp adjustably interconnected or fastened to one another which can be clamped to the support surface. The mounting clamp may be moved or adjusted relative to the wheel bracket to fit or clamp to support surfaces having different widths or dimensions. The wheel bracket includes a pair of extension arms extending outward in a laterally spaced relation to one another defining a wheel receiving space.