Radial tire definition
A type of tire construction which has the main carcass plies or cords which run at right angles to the bead and parallel to the radius. By itself, this construction is very weak because when the bias angle is smaller, the structure is stiff. However, the radial tire has a very large bias angle. In order to strengthen the tire, a belt surrounds the circumference. This belt is made of low-angle plies (usually about 15 degrees). In this way, the tread area is stiff and the sidewall are flexible. In this way they can act independently of each other. In a P185/80R13 tire, R indicates a radial tire.