| CPC B60C 11/0302 (2013.01) [B60C 11/1204 (2013.01); B60C 11/1236 (2013.01); B60C 2011/0362 (2013.01); B60C 2011/0367 (2013.01); B60C 2011/1213 (2013.01); B60C 2011/1254 (2013.01)] | 18 Claims |
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1. A tire, comprising:
a tread pattern comprising an inclined groove group in which a plurality of sets of inclined grooves, which extends from a starting end in a center region including a tire equator line toward both sides in a tire width direction and toward a first side in a tire circumferential direction across the tire equator line to a pattern end of a tread portion, is disposed in the tire circumferential direction;
a periphery distance from the tire equator line to the pattern end at one side in the tire width direction being L, an inclination angle of the inclined grooves with respect to the tire circumferential direction being
(a) greater than 40 degrees and 50 degrees or less in a first range from the starting end to a position separated in the tire width direction by 35% of the periphery distance L,
(b) greater than 50 degrees and 65 degrees or less in a second range from an outer side in the tire width direction of the position separated from the tire equator line in the tire width direction by 35% of the periphery distance L to a position separated from the tire equator line in the tire width direction by 50% of the periphery distance L,
(c) greater than 65 degrees and 80 degrees or less in a third range from an outer side in the tire width direction of the position separated from the tire equator line in the tire width direction by 50% of the periphery distance L to a position separated from the tire equator line in the tire width direction by 70% of the periphery distance L, and
(d) greater than 80 degrees and 90 degrees or less in a fourth range from an outer side in the tire width direction of the position separated from the tire equator line in the tire width direction by 70% of the periphery distance L to a position separated from the tire equator line in the tire width direction by 100% of the periphery distance L, and
a circumferential-direction distance along the tire circumferential direction from the starting end to a terminating end of the inclined grooves in the pattern end being from 60% to 90% of a width-direction distance along the tire width direction from the starting end to the terminating end; wherein
the tread pattern includes a plurality of sipes provided in a region of a land portion between inclined grooves adjacent in the tire circumferential direction, and
a value obtained by dividing a total length (mm) of lengths projected in the inclination direction A, which is inclined at an angle α (α=0 or more and less than 360 degrees) with respect to the tire width direction, of all grooves provided in the tread pattern by (ground contact width×circumferential length) (mm2) is ρg, a value obtained by dividing a total length (mm) projected in the inclination direction A of all the sipes provided in the tire by (ground contact width×circumferential length) (mm2) is ρs, an average depth (mm) of grooves is Dg, a snow traction index STI is defined by the following Formula (1),
STI=−6.8+2202*ρg+672*ρs+7.6*Dg (1), and
a value of the snow traction index STI at the angle α=30 to 40 degrees is from 104% to 110% of a value of the snow traction index STI at the angle α=0 degrees.
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