Heavy-duty pneumatic tire

A heavy-duty pneumatic tire comprising:

• a tread portion comprising a plurality of main grooves extending straight and continuously in a tire circumferential direction, and a plurality of ribs divided by the main grooves, wherein
• the ribs include a crown rib arranged closest to a tire equator and at least one middle rib arranged adjacently to the crown rib,
• the crown rib is provided with crown sipes crossing the crown rib in a tire axial direction and arranged separately from each other in the tire circumferential direction,
• the at least one middle rib is provided with middle sipes crossing the at least one middle rib in the tire axial direction and arranged separately in the tire circumferential direction and middle shallow grooves having a smaller depth and a larger width than the middle sipes,
• the middle shallow grooves comprise a circumferential middle shallow groove extending in the tire circumferential direction so as to divide the at least one middle rib into an inner portion and an outer portion in the tire axial direction and lateral middle shallow grooves extending from an axially inner side edge of the at least one middle rib to the circumferential middle shallow groove so as to terminate at a position thereof,
• at least one of the middle sipes is formed in an S-shape and includes an arc-shaped curved portion intersecting an axially extending reference line on one side in the tire axial direction and an arc-shaped curved portion intersecting the axially extending reference line on the other side in the tire axial direction,
• the axially extending reference line passes through both ends of the middle sipe,
• each of the crown sipes is inclined to one side with respect to the tire axial direction,
• the crown rib is provided with crown shallow grooves arranged separately from each other in the tire circumferential direction, and
• each of the crown shallow grooves comprises a pair of end portions and a middle portion arranged between the pair of the end portions so as to connect them, wherein the end portions are inclined to the one side and the middle portion is inclined to the other side with respect to the tire axial direction.