An apparatus of the present invention is designed for assembling tires having a pair of spaced beads of various diameters and configurations with the respective wheels having a pair of seats moveable by a conveyor along an assembly path. A mounter station is disposed on the conveyor and presenting an alignment axis. A sealing mechanism is cooperable with the mounter station and is moveable around the alignment axis by a drive unit connected thereto for forcing at least one of the beads of the tire between the seats of the wheel. The apparatus accommodates a wide variety of wheel and tire sizes, is not complex and bulky, and reduces number of parts required to form the apparatus.