Pneumatic tire

摘要

A pneumatic tire is provided on the tread portion (2) with
a pair of crown circumferential grooves (3) that extending on either side of the tire equator (C);a pair of shoulder circumferential grooves (4) each extending between the crown circumferential groove (3) and a ground-contacting end (2t);a crown rib (5) extending between the crown circumferential grooves (3);middle ribs (6) each extending between the crown circumferential grooves (3) and the shoulder circumferential grooves (4); andshoulder ribs (7) each extending between the shoulder circumferential groove (4) and the ground-contacting end (2t).

The groove volume ratio Rc of the crown rib, which is a ratio of the total volume of the grooves and sipes provided on the crown rib to the rib volume of the crown rib (5),

the groove volume ratio Rm of the middle rib (6), and

the groove volume ratio Rs of the shoulder rib (7)

satisfy the relationship,
Rc<=Rm

主权项

1. A pneumatic tire comprising a tread portion provided with:
a pair of crown circumferential grooves extending continuously in a tire circumferential direction on either side of a tire equator; a pair of shoulder circumferential grooves extending continuously in the tire circumferential direction between said crown circumferential groove and a tread ground-contacting end on each side of the tire equator; a crown rib extending continuously in the tire circumferential direction between said crown circumferential grooves; a pair of middle ribs each extending continuously in the tire circumferential direction between said crown circumferential groove and said shoulder circumferential groove on each side of the tire equator, each of the middle ribs being provided with (i) an inner middle sipe extending outward in the tire axial direction from said crown circumferential groove and terminating without reaching said shoulder circumferential groove and (ii) an outer middle sipe extending inward in the tire axial direction from said shoulder circumferential groove and terminating without reaching said crown circumferential groove, wherein (a) the outer middle sipe has a width larger than that of the inner middle sipe, (b) the outer middle sipe and inner middle sipe are inclined with respect to an axial direction of the tire, and (c) the outer middle sipe is inclined in an opposite direction of the inner middle sipe; and a pair of shoulder ribs each extending continuously in the tire circumferential direction between said shoulder circumferential groove and said tread ground-contacting end on each side of the tire equator, wherein a groove volume ratio Rc of the crown rib, which is a ratio of the total volume of the grooves and sipes provided on the crown rib to said the rib volume of the crown rib, a groove volume ratio Rm of the middle rib, and a groove volume ratio Rs of the shoulder rib satisfy the relationship Rc≦Rm