"On a radial tire, the plies are run from bead to bead directly across the tire (radially). In other words, the cords are perpendicular to the bead. Successive plies are just layered over the existing ones with all cords being parallel. A bias ply tire runs the plies at an angle to the bead (biased). Different layers have opposing angles, criss-crossing across the tire.
On an unbelted tire, like most bias ply designs, the tread rubber is molded right on top of the plies. For a belted tire, like a radial, a flat layer of material, usually a steel mesh, is placed between the body and tread. The belt is just a weave of metal fibers that overlap in a pattern very similar to the criss-crossing bias ply material. Each belt adds an additional layer in the tread area but leaves the sidewall area untouched."
If you ever driven on a bias ply you will not forget it. Scary as hell compared to a radial.
