Abstract: An ordinarily uncovered recess of a deeply recessed drive axle wheel of a heavy road vehicle is covered by a hub cap secured in place by nuts applied to externally threaded ends of respective extenders which pass through accommodating holes in the hub cap. The extenders are secured in place by having their opposite ends internally threaded and screwed onto the free ends of the usual lug bolts that extend beyond the usual lug nuts adjacent to the bottom of the recess. In this way, auxiliary valve stems can be mounted in receiving openings in the hub cap, so as to face externally of the wheel for convenient testing of tire air pressure and convenient filling with air when required, and uniformity of undercarriage appearance for the vehicle is achieved. The invention includes the method of mounting and a kit of parts required for carrying out the method. It is preferred that the hub cap securement nuts applied to the extenders be respective pairs of interlocking nuts made of a nylon type of plastic.