Heavy duty pneumatic tire having tread with shoulder ribs

A heavy duty pneumatic tire including in its tread at least one circumferential main groove extending in a circumferential direction, and shoulder rib grooves extending in the circumferential directions and spaced from the circumferential main groove and arranged in the proximity of tread ends to define shoulder ribs, wherein said shoulder rib grooves fulfill relationships:

• Rw/W=0.28-0.35
• Rs/W=0.05-0.12
• Rd/W=0.07-0.19
• where a distance from an equatorial plane to the tread end of the tire is W mm, a distance from the tread end to the shoulder rib groove is Rw mm, a width of the shoulder rib groove is Rs mm and a depth of the shoulder rib groove is Rd mm, and wherein angles .alpha. and .beta. made by normal lines to surfaces of the tread and opposite walls of the shoulder rib grooves fulfill relations -7.degree..ltoreq..alpha. and .beta..ltoreq.7.degree., respectively, wherein each of the shoulder rib grooves comprises a number of sections each consisting of a straight portion extending substantially in parallel with the equatorial plane of the tire, a short inclined portion obliquely contiguous to the straight portion, a long inclined portion obliquely contiguous to the short inclined portion, and another short inclined portion obliquely contiguous to the long inclined portion and contiguous to a straight portion of another section with the inclined portions arranged alternately in opposite directions to each other.