A tire, and an apparatus and method for forming a tire. The tire may either be a tubed or tubeless tire, and is filled with a mixture of virgin rubber and small rubber pieces. Preferably, a machine grinds the core of used flatproofed tires, or pieces thereof, into a finely communicated pulverulent. The pulverent is mixed with liquid virgin flatproofing material, such as a polyurethane. An injector introduces this mixture, into the core of a tire, typically through a valve. The core of the tire is preferably substantially filled with this mixture. The injector may take the form of one or more elongated screws and the mixing may occur as the ground rubber is being conveyed by the screw.