Truck tire and tread for steer axles

A pneumatic radial ply track tire for use on steering axles, comprising a tread, a casing, the casing having two sidewalls, one or more radial plies extending from and wrapped about two annular beads and a belt reinforcement structure located radially between the tread and the plies, the tread characterized by:

• a plurality of circumferentially continuous grooves;
• a pair of radially recessed ribs, the radially recessed ribs being radially recessed and non-road contacting under static load;
• a pair of narrow circumferential decoupling grooves, one circumferential decoupling groove being adjacent each recessed rib;
• and
• a plurality of tread ribs, including a pair of shoulder ribs, one shoulder rib being adjacent each narrow circumferential decoupling groove, the radially outer surfaces of the plurality of tread ribs defining a radially outer tread surface, the outer tread surface being adjacent to and extending between the pair of narrow circumferential decoupling grooves, the distance halfway between the narrow decoupling grooves defining the centerline of the tread, in a cross section of the tread, the radially outer tread surface has a maximum diameter D at the tread centerline and a constant internal radius of curvature Ri extending laterally toward each narrow circumferential decoupling groove, the constant internal radius of curvature originating on the centerline of the tread, at a point located on at least one-half of the tread, the curvature of the radially outer tread surface changes wherein the tread surface has a radius of curvature Re originating external to the tire, the external radius of curvature Re being at least greater than D and extending laterally over a majority of the shoulder rib to the adjacent narrow decoupling groove increasing the radial thickness (t) of the shoulder rib progressively from the point of curvature change to a maximum radial thickness (t max), the maximum radial thickness (t max) being adjacent the narrow decoupling groove, the tread exhibiting a pressure distribution in a static footprint of the tire, when the tire is normally inflated and normally loaded such that the pressure exerted at the circumferential center of the footprint at the shoulder rib adjacent the narrow decoupling groove is P.sub.3, on the shoulder rib adjacent the continuous groove is P.sub.1, the pressure on the rib laterally adjacent the shoulder rib at the
• groove being P.sub.2 wherein P.sub.1 about equals P.sub.2 and P.sub.3 is greater than P.sub.1 by at least about 200% but less than 400% P.sub.1.