Semi-automatic tyre changer for truck and bus wheels Self-centering chuck to lock grooved and split ring rims from 13” to 27”, 2-speed rotation in both directions of the self-centering chuck and automatic traversing of the tool-holder carriage. TOOL-HOLDER CARRIAGE Automatic translational movement of the tool-holder carriage controlled by the on-purpose control unit. Manual lifting and traversing of the tool-holder arm, which can be secured in 3 different working positions. TOOL-HOLDER ARM Tool-holder arm lifting and tool rotation are manually achieved through an on-purpose unlocking device. The special conical shape of the bead breaker disc allows to obtain an easy dismounting of split ring rims. BRONZE BEARINGS The chuck rotation housings are made in bronze. This device increases considerably the duration and reduces substantially any eventual mechanical play. INCREASED CARRIAGE STROKE The tool-holder carriage stoke has been increased in order to easily operate on wheels up to 1300 mm width.