In the early development stage of Hot Wheels, one of the chief goals was to develop cars that could be rolled easily. Engineers would have races to see whose design was the fastest. One of Howard’s designs used an axle made of 0.020” music wire. He devised a torsion-bar spring-action layout, which proved to be very durable. When cars were dropped, the wheels moved upward until impacting the inner fender well, so the impact loads were distributed into the body without damaging the axle.