| 摘要 |
This invention reveals a pneumatic tire having an outer circumferential tread wherein said tread is a sulfur-cured rubber composition comprised of, based on 100 parts by weight of rubber, (1) from about 5 to about 50 parts of 3,4-polyisoprene rubber, wherein said 3,4-polyisoprene rubber has (a) a 3,4-isomer content of from 75 percent to 95 percent, (b) a 1,1- isomer content of from 5 percent to 25 percent, (c) a glass transition temperature from 0 degree to 25 degree C and (d) a number average molecular weight which is within the range of 30,000 to 180,000; and (2) from about 50 to about 95 parts of a rubbery polymer which is co-curable with the 3,4-polyisoprene rubber. The subject invention further discloses a pneumatic tire having an outer circumferential tread wherein said tread is a sulfur-cured rubber composition comprised of, based on 100 parts by weight of rubber, (1) from about 20 to about 60 parts of natural rubber, (2) from about 5 to about 30 parts of high cis-1,4-polybutadiene rubber, (3) from about 10 to about 50 parts of styrene-butadiene rubber, and (4) from about 5 to about 30 parts of 3,4-polyisoprene rubber, wherein the 3,4-polysoprene rubber has (a) a 3,4-isomer content of from 75 percent to 95 percent, (b) a 1,2-isomer content of from 5 percent to 25 percent , (c) a glass transition temperature from 0 degree to 25 degree C and (d) a number average molecular weight which is within the range of 30,000 to 180,000.
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