Abstract: A new pneumatic radial ply truck tire 10 for use on steering axles is disclosed. The tire 10 has a 20 tread having a plurality of circumferentially continuous grooves 22, a pair of narrow circumferential decoupling grooves 24, a pair of radially recessed ribs 21, and a plurality of tread ribs 25,25A. The tread 20 has a radially outer tread surface 30 having a curvature defined by an internal radius of curvature Ri and an external radius of curvature Re, Re extending laterally over a majority of a shoulder rib 25A to the narrow decoupling groove 24 on at least one-half of the tread 20, preferably both tread halves. The shoulder rib 25A has a thickness (t) at the circumferential groove 22 which progressively increases to a thickness (t max) adjacent the narrow decoupling groove 24. The tread 20 exhibits a pressure distribution in the shoulder region which is complimentary to uniform wear.