The outer tube is made of wear-resistant rubber with a high strength and elastic outer shell, which directly contacts the ground and protects the inner tube from damage. It is composed of tire beads, buffer layers, tread, and tire fabric layers (see Figure 2 of the Inner Tube Tire Atlas (Figure 1- Tire Beads, 2- Buffer Layer, 3- Tread, 4- Cord Layer, 5- Crown, 6- Shoulder, and 7- Sidewall).

① Tread: The tread is the outer surface of the outer tire, including the crown, shoulder, and sidewall. The tire crown, also known as the driving surface, is in direct contact with the road surface, withstands impact and wear, and protects the tire body from mechanical damage. In order to increase the adhesion between the tire and the road surface and prevent longitudinal and transverse slip, various forms of patterns are made on the tire crown (see Figure 3 of the inner tube tire atlas (a - regular pattern, b - mixed pattern, c - off-road pattern)). The tire shoulder is the transitional part between the thicker tire crown and the thinner sidewall, and generally has various patterns to prevent slipping and dissipate heat. The sidewall is a thin rubber layer attached to the sidewall of the tire fabric layer, which protects the tire fabric layer from mechanical damage and moisture erosion. The tire side does not come into contact with the ground and generally does not wear, but it bears significant bending deformation here.

② Cord layer: The cord layer is the skeleton of the outer tire, also known as the tire body, whose main function is to withstand loads (vehicle gravity, road impact force, and internal air pressure), and maintain the size and shape of the tire's outer edge. The cord layer is usually composed of multiple layers of glued cotton thread or other fiber woven fabric, and arranged crosswise at a certain angle. In order to evenly distribute its load, the number of ply cords is often even. The number of ply cords is determined based on the load the tire bears, internal pressure, and the type and purpose of the tire. Generally, the number of ply cords is indicated on the surface of the outer tire.

③ Buffer layer: The buffer layer is located between the tire tread and the tire fabric layer, which is soft and elastic. Its function is to strengthen the combination of the tire tread and the tire fabric layer, to alleviate the impact of uneven road surfaces on the car during driving, and to prevent the tire tread and tire fabric layer from detaching during emergency braking.

④ Beads: Beads are the foundation of the fabric layer. It is fixed on the wheel rim by the tire bead. The tire bead is composed of steel wire bead, cord layer edge wrapping, and tire bead wrapping.