#1 Tires

The earliest tires were bands of leather, then iron (later steel) placed on wooden wheels used on carts and wagons. The tire would be heated in a forge fire, placed over the wheel and quenched, causing the metal to contract and fit tightly on the wheel. A skilled worker, known as a wheelwright, carried out this work. Synthetic rubbers were invented in the laboratories of Bayer in the 1920s. In 1946, Michelin developed the radial tire method of construction. Michelin had bought the bankrupt Citroën automobile company in 1934, so it was able to fit this new technology immediately.