Heavy duty pneumatic tires

A heavy duty pneumatic tire comprising;

• lug grooves formed in each half region of a tread portion and separated from each other at a given interval in a circumferential direction of the tire, island portions defined by said lug grooves, an auxiliary groove connecting at least two lug grooves located in said half region of the tread portion and separated from each other in the circumferential direction of the tire to each other, said auxiliary grooves formed in a central region of the tread portion within a range of about 50% of a tread width, a step protrusion extending along the auxiliary groove and arranged at least inside the auxiliary groove, and a grove width W.sub.1 of the auxiliary groove, a groove depth d.sub.1 of the auxiliary groove from tread surface, a width W.sub.2 of a surface of the step protrusion and a height d.sub.2 from the bottom of the auxiliary groove to the surface of the step protrusion satisfy relationship of (W.sub.1 -W.sub.2)/2W.sub.1 <0.2 and 0.70<d.sub.2 /d.sub.1 <0.95, and said step protrusion has a length of not less than 30 mm and a width W.sub.2 of not less than 10 mm.