Inside the things of your world: Tires

It takes a lot more than rubber to make the 120-pound flexible containers of compressed air that keep you rolling safely and comfortably. Beneath the tread and inside the sidewall is a scientific and artful blend of rubber, steel and mysterious compounds whose recipes are closely guarded secrets of tire makers.

Tire materials begin with rubber – both natural and, to a lesser extent, synthetic. Tires also are fabricated with sulfur and sulfur compounds, silica, carbon black, resins, oil products, pigments and other materials. Engineers stay busy in their labs developing the 20 or more compounds – each with nine to 15 ingredients – that go into most truck tires.