Tractor and snow tires have especially deep grooves that enable the tire to move through soft earth or deep snow. The body gives the tire its strength and form. It consists of layers of fabric permeated with rubber. The fabric in most passenger-vehicle tire bodies is polyester. Each fabric layer is called a ply, and the strength of a tire is sometimes described by the number of plies in its body.
Most automobile tires have two plies.
The beads of a tire are the two bands that hold the tire to its wheel. They are located along the tire's inner edges and are made up of strands of wire surrounded by rubber and covered with fabric. Pneumatic tires are made in a variety of sizes. The letter P identifies the tire as a passenger-car tire. The number 205 is the width of the tire measured in millimeters.