The present invention relates to a radial ply tire (230) with a tread (232) subdivided transversely into a central portion (250) having central ribs (260a,260b), shoulder portions (254a, 254b) having shoulder ribs (270a,270b) and intermediate portions (252a, 252b) having intermediate ribs between the central portion and the shoulder portions. The tread has intermediate grooves (262a,262b) between the central ribs and the intermediate ribs (266a,266b) and shoulder decoupling grooves (264a,264b) between the intermediate ribs and the shoulder ribs (270a,270b). The shoulder decoupling grooves having a depth (D1) being less than the intermediate decoupling grooves whereby the footprint width of the tread surface can expand from first width (NLFPW) under normal load to a second width (HLFPW) under heavy load.