GERALD's TIRES & BRAKES

 

Before Michelin introduced the radial in 1946 most tires were "bias-ply". Bias-ply tires had many limitations like heat build up, tread wear problems, weak handling and overall ride comfort.

 

The primary difference between bias-ply and radial tires lies in the design of the tire's casing--the part of the tire underneath the tread that forms the foundation of the tire. The casing is made up of a series of cords which are combined to form layers or plies. In bias-ply tires, these plies are positioned so the cords run at angles to each other across the tire, in a criss-cross manner. In a radial tire, these plies are positioned so the cords run alongside each other in a series of circular bands or "hoops" across the tire. The top layers of the radial casing usually consist of steel belts made up of woven strands of steel cord.

 

The radial positioning for the plies and the layers of steel belts in a radial tire allow it to flex and absorb the irregularities of the road surface. Plies that are arranged radially also produce much less friction, resulting in longer tread life and increased fuel economy. Other advantages include better traction, handling and ride comfort.