What is a bias ply tire?

There are two basic types of tire construction that mud, all terrain and street tires use as their foundation. They are bias-ply and radial designs. Each type of tire construction has its own unique set of characteristics that are the key to its performance, whether on road or off road and these characteristics can help to define the purpose of the tire. The following information will explain what identifies the difference between a bias ply tire and a radial type tire. BIAS PLY The simple definition of a Bias Ply Tire: The bias ply tire construction utilizing rubber-coated layers known as plies composed of textile cords, usually nylon and sometimes Kevlar. The plies layered diagonal from one bead to the other bead at about a 30 degree angle. One ply is set on a bias in one direction as succeeding plies are set alternately in opposing directions as they cross each other and the ends are wrapped around the bead wires, anchoring them to the rim of the wheel. The layers of plies are them covered with more rubber to form the tread of the tire. Bias ply tires are sometimes called cross-ply tires. Performance and Purpose of a Bias Ply Bias ply tires have a limited purpose in life and are only used for specific purposes or jobs. The reason for this is because of its performance characteristics. However for some jobs the bias ply tire is an idea tire for the purpose such as for the tires of a towed trailer, farm equipment tires, some purpose built tires like extreme terrain tires and some forms of racing still use bias ply tires. The reasons for this limited use are: The bias-ply tire casing is constructed to form one working unit. When the sidewalls deflect or bend under load, the tread squeezes in and distorts. The distortion affects the tires footprint and can decrease traction and increases wear depending on the terrain. The tread distortion also causes abrasion from the ground surface, which reduces the life of the tire. These factors are why bias ply tires are not idea for passenger car tires or as tires that my see highway use unless used as tires for a towed trailer. Bias Ply Strength - The way to increase the strength of bias-ply tires is by increasing the number of plies and bead wires. More plies means more mass which, increasing heat retention and reducing tire life. Because of the bias ply inherent construction, sidewall strength is less than that of a radial tire's construction and cornering is significantly less effective. This is probably one of the main reasons bias ply tires are not used for passenger cars and trucks. However because of the bias ply construction and inherent strength of a properly inflated tire, the bias ply is idea for straight line towing.