A wheel service machine, in particular a balancing machine, to carry out operations on a wheel having a rim and a tyre, comprising: - a shaft connected to a drive motor unit to rotate about a longitudinal axis and designed to support the wheel in rotation; - an abutment element, connected to the shaft to rotate as one therewith and designed to come into abutment with the rim supported by the shaft; - a locking member, designed to be removably coupled to the shaft and configured to slide relative to the shaft along the axis between a locked position, where it is close to the abutment element in order to lock the rim, interposed between the abutment element and the locking member itself, and an unlocked position, away from the abutment element and not interfering with the rim; - an engagement element movably connected to the shaft to move parallel with the longitudinal axis and configured to be coupled to the locking member so as to drive the latter in motion; - a pneumatic actuator having a first and a second chamber (10A, 10B) connected to shaft to rotate as one therewith and connected to the engagement element to move it between the locked position and the unlocked position; - a high-pressure source; - a pneumatic circuit configured to selectively connect the first and second chambers (10A, 10B) of the pneumatic actuator to the high-pressure source, wherein the pneumatic circuit includes a rotary manifold having a stationary part and a rotating part and defining at least a first and a second duct (16A, 16B), each having an inlet (161 A, 161B) in the stationary part and an outlet (162A, 162B) in the rotating part, wherein the outlets (162A, 162B) of the first and the second duct (16A, 16B) are connected to the first and the second chamber (10A, 10B) of the pneumatic actuator, respectively, and the inlets (161 A, 161B) of the first and the second duct (16A, 16B) are selectively connectable to the high-pressure source, characterized in that the pneumatic circuit comprises at least a first retaining valve, located between the second chamber of the pneumatic actuator and the outlet of the second duct of the rotary manifold and configured to determine, in at least one operating configuration of the pneumatic circuit, a difference in pressure between the second chamber of the pneumatic actuator and the second duct of the rotary manifold. - a shaft connected to a drive motor unit to rotate about a longitudinal axis and designed to support the wheel in rotation; - an abutment element, connected to the shaft to rotate as one therewith and designed to come into abutment with the rim supported by the shaft; - a locking member, designed to be removably coupled to the shaft and configured to slide relative to the shaft along the axis between a locked position, where it is close to the abutment element in order to lock the rim, interposed between the abutment element and the locking member itself, and an unlocked position, away from the abutment element and not interfering with the rim; - an engagement element movably connected to the shaft to move parallel with the longitudinal axis and configured to be coupled to the locking member so as to drive the latter in motion; - a pneumatic actuator having a first and a second chamber (10A, 10B) connected to shaft to rotate as one therewith and connected to the engagement element to move it between the locked position and the unlocked position; - a high-pressure source; - a pneumatic circuit configured to selectively connect the first and second chambers (10A, 10B) of the pneumatic actuator to the high-pressure source, wherein the pneumatic circuit includes a rotary manifold having a stationary part and a rotating part and defining at least a first and a second duct (16A, 16B), each having an inlet (161 A, 161B) in the stationary part and an outlet (162A, 162B) in the rotating part, wherein the outlets (162A, 162B) of the first and the second duct (16A, 16B) are connected to the first and the second chamber (10A, 10B) of the pneumatic actuator, respectively, and the inlets (161 A, 161B) of the first and the second duct (16A, 16B) are selectively connectable to the high-pressure source,