Abstract: A tool for inserting valve stems in the wheel rim of a tubeless tire and wheel combination comprises a tubular body having a tapered inner peripheral wall and an end portion adapted to be received in the stem hole of the wheel rim. The other end of the tubular body has a threaded aperture adapted to receive a threaded shaft therethrough. The shaft is adapted to engage the end of a valve stem and as it is rotated to drive it axially through the tubular body. As a result, the resilient, spaced apart ribs at the other end of the valve stem are axially compressed as they are driven through the stem hole in the wheel. Once the end most rib has protruded outwardly from the end of the tubular body, and expands on the inner side of the wheel rim wall, the tube is removed from the stem hole and the shaft is further rotated to extract the innermost rib from the end of the housing whereby the innermost rib expands on the opposite side of the wheel rim wall to thereby mount the valve stem to the wheel rim.