A robotic wheel gripper unit configured for gripping and transporting a wheel to a predetermined position; comprising: a selectively moveable arm; and a gripper tool that is connected to a first end of the moveable arm; wherein the gripper tool further comprises a plurality of gripper fingers having a top end mounted to platforms that are selectively moveable from a releasing position to a gripping position, wherein the gripper fingers are configured for selectively engaging a portion of a wheel; and wherein the gripper tool further comprises at least one optical sensor that is configured to detect a location of a predetermined element on the wheel; wherein the sensor is mounted to a sensor plate, the sensor plate extending downwardly from one of the platforms, and positioned rearward of the gripper fingers, between the gripper fingers, adjacent gripper grooves on the gripper fingers, that are configured to engage with the portion of the wheel when the gripper fingers are in the gripping position, to direct a beam of light to the wheel,and characterised in that the sensor is configured to locate a tire pressure monitor system valve stem on the wheel, and in that the robotic wheel gripper unit further comprises a controller to which the sensor is operatively connected and that is configured to record the position of the tire pressure monitor system valve stem with respect to a fixed position and that is configured to control the gripper tool such that the gripper tool may position the wheel on an assembly conveyor in a predetermined position to locate the tire pressure monitor system valve stem at a predetermined orientation during an assembly operation with a tire. a selectively moveable arm; and a gripper tool that is connected to a first end of the moveable arm; wherein the gripper tool further comprises a plurality of gripper fingers having a top end mounted to platforms that are selectively moveable from a releasing position to a gripping position, wherein the gripper fingers are configured for selectively engaging a portion of a wheel; and wherein the gripper tool further comprises at least one optical sensor that is configured to detect a location of a predetermined element on the wheel; wherein the sensor is mounted to a sensor plate, the sensor plate extending downwardly from one of the platforms, and positioned rearward of the gripper fingers, between the gripper fingers, adjacent gripper grooves on the gripper fingers, that are configured to engage with the portion of the wheel when the gripper fingers are in the gripping position, to direct a beam of light to the wheel,and characterised in that the sensor is configured to locate a tire pressure monitor system valve stem on the wheel, and in that the robotic wheel gripper unit further comprises a controller to which the sensor is operatively connected and that is configured to record the position of the tire pressure monitor system valve stem with respect to a fixed position and that is configured to control the gripper tool such that the gripper tool may position the wheel on an assembly conveyor in a predetermined position to locate the tire pressure monitor system valve stem at a predetermined orientation during an assembly operation with a tire.