Heavy duty pneumatic tire

A heavy duty pneumatic tire comprising:

• a tread having a tread surface that comes into contact with a road surface;
• and
• a belt located radially inward of the tread, wherein
• shoulder circumferential grooves extending in a circumferential direction are formed on the tread, thereby forming shoulder land portions each including an end of the tread surface and middle land portions located inward of the shoulder land portions in an axial direction,
• each of the shoulder land portions includes a groove wall portion forming a wall of the shoulder circumferential groove, and a cap portion located outward of the groove wall portion in the axial direction,
• wherein wear resistance indexes of the groove wall portion and the cap portion are obtained by an improved Lambourn abrasion test specified in JIS K6264-2, and the wear resistance index of the groove wall portion is lower than the wear resistance index of the cap portion,
• a ratio of a distance in the axial direction from an outer edge of the shoulder circumferential groove to a boundary between the groove wall portion and the cap portion on an outer surface of the shoulder land portion, to a width in the axial direction of the shoulder land portion, is not less than 20% and not greater than 30%, and
• the distance in the axial direction from the outer edge of the shoulder circumferential groove to the boundary between the groove wall portion and the cap portion increases from a bottom of the shoulder circumferential groove to a top of the shoulder circumferential groove.