Wheels, beautiful wheels, flashing spokes, whirling, sparkling shapes in motion—their variety has become practically endless. There are cast wheels, traditional wire wheels, die-stamped wheels, even rotary forged or spun wheels. There are wheels with CNC-machined spokes, wheels with slots and fins and stars. Lots to see, but what is there to know about wheels? How are they made? What are their strengths and weaknesses? How are they tested? And perhaps most important of all, why should I care?