Cooper Discoverer A/T3 Traction Radial Tire - 31/105R15 109R Tire only Modern, aggressive 5-rib all-terrain design to provide outstanding performance in both on-road and off-road driving applications. Silica based tread compound provides excellent wet traction and handling on the highway, while also improving cut and chip resistance in more harsh rocky and gravel terrain. Broken center rib improves soft surface traction without sacrificing handling. Dual draft tread element walls aid in reducing stone retention, stone drilling and assist in cut and chip resistance.