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 who 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. This proved to be very durable. When cars were dropped, the wheels moved upward until contacting the inner fender well, so the impact loads were distributed into the body without damaging the axle.