A device for locking wheel rims for vehicles on repair workshop machines, has a supporting structure rotating around a work axis with a repair workshop machine or the like and has a resting portion for a wheel rim for vehicles, a locking element removably connected to a fastening element on the supporting structure, and a movement arrangement. The movement arrangement has a main actuator cylinder with fluid operation suitable for moving the fastening element from a release position, wherein the locking element is disengaged from the rim, to a retention position, wherein the locking element is engaged on the rim, an auxiliary actuator cylinder with fluid operation suitable for moving the fastening element from the release position to the retention position of the rim, and a feeding mouth for a fluid connected to one of the main actuator cylinder and the auxiliary actuator cylinder.