Apparatus for inflating a wheel-mounted tire on a high production basis comprises a platen supported on a frame beneath an inflation head on which the wheel-mounted tire is received. The platen has internal air passages opening opposite a fixed support plate of the frame through which pressurized air is directed to selectively float the platen above the support plate to facilitate near-frictionless horizontal movement of the platen in all radial directions. A centering device locates the wheel-mounted tire precisely in line with the inflation head after which the air is discontinued to lower the platen back onto the support plate. The inflation head is then operated to inflate the tire. The platen is refloated and centered in a home position by a platen centering device.