Studless winter tire
A studless winter tire that has enhanced performance on ice and snow both initially and after degradation while maintaining good abrasion resistance is provided. The studless winter tire includes: a cap tread formed from a rubber composition A; and a base tread formed from a rubber composition B. The studless winter tire satisfies the following formulas (1) and (2): (1) a×c/100<b×d/100; and (2) a≥8, where a represents the softener content (% by mass) based on 100% by mass of the rubber composition A; b represents the softener content (% by mass) based on 100% by mass of the rubber composition B; c represents the percentage by mass (% by mass) of the cap tread based on the entire tread; and d represents the percentage by mass (% by mass) of the base tread based on the entire tread.
1. A studless winter tire comprising:
a cap tread formed from a rubber composition A; and
a base tread formed from a rubber composition B,
wherein the studless winter tire satisfies the following formulas (1) and (2):
a×c/ 100< b×d/ 100; and (1)
a≥ 8 (2)
wherein a represents the softener content (% by mass) based on 100% by mass of the rubber composition A;
b represents the softener content (% by mass) based on 100% by mass of the rubber composition B;
c represents the percentage by mass (% by mass) of the cap tread based on the entire tread; and
d represents the percentage by mass (% by mass) of the base tread based on the entire tread, and
wherein the rubber composition A contains silica, and d is less than 70% by mass.
2. The studless winter tire according to claim 1 ,
wherein the rubber composition A comprises:
natural rubber in an amount of 30 to 80% by mass based on 100% by mass of a rubber component of the rubber composition A; and
polybutadiene rubber in an amount of 20 to 70% by mass based on 100% by mass of the rubber component.
3. The studless winter tire according to claim 1 , wherein the silica has a nitrogen adsorption specific surface area (N 2 SA) of 40 m 2 /g or more, and the silica is in an amount of 10% or more by mass based on 100% by mass of a rubber component of the rubber composition A.
4. The studless winter tire according to claim 1 , wherein c is no less than 35% by mass.
5. The studless winter tire according to claim 1 , wherein a×c ranges from 6 to 13.
6. The studless winter tire according to claim 1 , wherein b×d ranges from 7 to 13.