Abstract: Employee #1 was replacing four 750 by 16 Tracker T tires on rims using a Coats RC-15A rim clamp machine. Five tires (including the spare) had been removed from truck's rims. Two new tires were then mounted on the rims. While mounting and inflating the third tire, the rim vaulted off the machine and struck the face of Employee #1 and then hit the ceiling of the service area. Employee #1 required hospitalization and reconstructive surgery. Employee #1 attempted to mount a 16-inch tire on a 16.5-inch spare tire rim. The tire bead did not properly seat. Management did not properly train employees to carefully inspect tires and rims to ensure that the tires were free of defects and the same size before mounting them.