Understanding proper tire maintenance, selection, and safety start with knowing the basics. Why are tires important? How do I choose the right set for my vehicle?
Tires are a driver’s first and only contact with the road, transferring actions such as steering, braking, accelerating, and turning. They are specifically chosen for each vehicle, making tires one of the most important safety features on a vehicle.
Parts of a Tire
A rubber-coated loop of high-strength steel cable that allows a tire to stay “seated” on a rim.
We’ll start from the inside out! Tire beads hold the tire to the rim or the outer edge of the wheel. They’re made of copper, brass, or bronze-plated high tensile steel wires wound into a rubber band. Tire beads prevent the tire from sliding out of place when the wheel rolls.
Tire Bead Filler
Bead filler is a rubber compound inside the tire’s beads. It provides stability to the lower sidewall and bead area. The density and stiffness of a tire’s bead filler help to determine a tire’s performance characteristics.
Tire Body Plies
This is the tire itself, made up of several layers of plies. Plies, like polyester cord, run perpendicular to the tire’s tread and are coated with rubber to help bond with other plies and belts to seal in the air. Plies give tires strength and resistance to road damage.
The cord body gives the tire strength and transmits cornering forces from the tread to the wheel. Rubber-coated fabric cord, called body plies, make up the cord body. Body plies can be made of polyester, rayon, or nylon. Polyester is most commonly used.
Tire Inner Liner
This is the innermost layer of a tubeless tire that prevents air from penetrating the tire.
The inner liner (in the center of the tire diagram) is a rubber compound bonded to the inside of the cord body that retains air under pressure. It has no cord reinforcement, and it functions as an inner tube. Note, however, that modern car tires no longer have inner tubes inside them. A tire’s beads, bead filler, and inner liner work together to hold air within the tire walls.
Belt plies are two or more strong layers of cord just under the tread area of the tire. The primary function of belt plies is to provide strength and stability to the tire tread. They play a role in improving tire mileage, impact resistance, and traction. Steel is the most common cord material used in belt plies.
Sipes are special treads within the tread that improve traction on wet, dirty, sandy, or snowy road surfaces.
The spaces between two adjacent tread ribs are also called tread grooves. These allow water to escape effectively.
The outer edge of the tread wraps into the sidewall area.
The sidewall of the tire protects cord plies and features tire markings and information such as tire size and type.
The area of a tire from the bead to the tread on the side of the tire is called the sidewall. It forms a protective covering for the cord body. Information about the tire is printed on the sidewall. This information includes the tire size, load index, and speed rating. Sidewall rubber compounds are designed to resist damage from ozone, cuts, and snags.
The portion of the tire that comes in contact with the road.
The tread is the portion of the tire that comes in contact with the road surface. The tread’s compound and its design have to balance wear, traction, handling, fuel economy, resistance, and other characteristics of the tire. Tread designs vary greatly!
For example, Destination LE2 all-season tires need to perform well in both wet and dry road conditions. They have circumferential tread grooves. These grooves allow water to pass through and stay off the tread.