Bias ply tires were common for cars built before the mid '70s, and radial tires took over from there. The internal construction is the main difference between the two tires, as the bias ply tire features ply cord (generally made of nylon or polyester) that runs at a 45 degree angle from the tire's bead. These ply cords overlap in a criss-cross pattern, most of the time with four plies total. The cord inside radial tires is positioned 90 degrees from the bead, which allows the tire to conform to the road much better. Most of the time, radial tires also have a steel belt that runs beneath the tread to help strengthen the tire. In general, radials are preferred for driving comfort, but bias ply tires are much more authentic. Coker Tire carries a wide selection of bias ply AND radial tires to meet your needs, whether you want period-correct tires or the comfort of a modern radial.