Abstract: A system for mounting the wheel rim of a tire assembly on the drive spindle of a tire correction machine including an adapter unit comprising a base assembly slidably receivable over the drive spindle with a plurality of elongate locating pins adjustably mounted on the base assembly to extend through the wheel rim lug holes and a plurality of hold down tubes slidably received over the locating pins to engage the lug holes and locate them concentrically of the drive spindle axis together with a hold down member and a locking member threadedly engaging the base assembly to clamp the wheel rim between the hold down tubes and base assembly. The system also includes a gaging unit adapted to provide a readout that allows the mounting adapter to be preadjusted to mount the wheel rim.