Much of the information we cover is about the outside of the tire; now we’re going to talk about the inside. This tire construction page is dedicated to understanding what goes into building your tire, and what’s inside it. There’s a lot of information, so we’ll start with the outside and continue moving in.
- The Tread – Containing two rubber compounds (for the tread base and tread cap), the tread covers the top of the belt system and increases stability as well as durability. During the curing process, the tread pattern and tread rubber cap are molded together. The cap is constructed with a rubber compound that offers more grip, which works with the base to provide mileage and traction.
- The Belt System – Its main function is to provide stability to the tire tread, which has an impact on function, handling, and tire wear. The belt system is placed on top of the casing and is commonly made of steel, which adds strength and stability without being too heavy.
- The Tire Casing – This is the body of the tire, and is made of the inner liner, the bead, and the sidewall, which loop together around the bead bundle to stay snugly in place.
- The Body Ply – These are cords comprised of nylon, polyester, or rayon. They add strength to the rubber compound casing.
- The Inner Liner – This is a rubber sheet that helps contain the tire pressure inside to minimize diffusion.
- The Beads – These help secure the tire to the wheel. The bead is the edge of the tire that meets the wheel, and is made with large steel cords woven together like a cable. The bead filler is made of a rubber compound and it extends into the tire’s sidewall.
- The Sidewall – The tire sidewall provides lateral stability to the tire, prevents air from escaping, and also protects the body plies. Some sidewalls are more flexible than others (for instance, UHP sidewalls may include steel or nylon to increase steering response time). Sidewalls also feature important information about the tire such as tire size and type.
Note: LT tires (commercial applications) sometimes have an extra belt, an extra casing ply, a stronger belt steel cord, and/or larger bead with more sidewall rubber, with the purpose of being able to support a greater load.