In a bias-ply tire the cords in a single ply run diagonally from the beads on one inner rim to the beads on the other. However, the orientation of the cords is reversed from ply to ply so that the cords crisscross each other. This construction provides longer tread wear but a rougher ride. 3 Pneumatic tires are made in a variety of sizes to accommodate a variety of vehicles. In addition, an alphabetic speed rating and a numeric tread-wear rating are embossed on the outer wall of the tire.
Most tires are of the balloon type, with a large cross section and thin sidewalls.
The large size permits a low inflation pressure, and the increased tread area gives better traction and braking qualities. Excessive tire wear is caused by incorrect inflation, wheel misalignment, sudden braking, and high speeds. 4 The Columbia Encyclopedia, Sixth Edition.