A NEW method of rating passenger-car tires is suggested by the author in which horsepower as well as load is used as a governing factor. Tires rated by this method, he believes, will give more nearly equal service on all makes and models of automobiles. Horsepower of the car, he explains, was felt to be the factor most likely to be representative of the acceleration, cruising speed, and top speed of the vehicle.
Mr. Roberts' paper presents a comprehensive review of tire design and development. Functional units of a tire are taken up one by one-body plies, tread plies, cushion, bead wire, reinforce, chafers, sidewall, and tread. Fundamental factors that affect tire service are discussed, such as load, inflation, speed, and atmospheric temperature, as well as neglect, abuse, horsepower, and road surface. The author also considers the various types of tire failures; a graphic method of measuring tread movement; tire development and improvement; costs; and tailoring the tire to the car.