Bias Ply Tires

There are three general methods of arranging or laying down the tire plies. They may be laid down "on the bias," "on the bias and belted," or "radially." The standard, and least expensive, tire is a bias ply. In this type of ply, the cord strips are arranged diagonally (i.e., at a bias) to the center line of the tread and alternate plies are reversed to cross at a 30 or 40 degree angle. The result is a uniformly firm body, which will wear satisfactorily at moderate speeds, with sidewalls that can stand curb bruises. In fast driving or hard turning, however, the tread elements squirm together and spring apart, producing heat that weakens the tires. A veterinarian named John Dunlop in Belfast, Ireland gets credit for inventing the pneumatic tire. In 1888 he tried making better tires for his son's bicycle by using linen-covered sheet rubber. Although he was granted a patent for bicycle and tricycle tires, he sold his idea in 1889. The man he sold it to was named Harvey du Cros, Jr., who started the Dunlop Rubber Company. Dunlop himself was never part of the company.