| 摘要 |
Provided is a sidewall insert and bead rubber composition for a runflat tire which is improved in rolling resistance, fatigue resistance, crack resistance, heat build-up and is lowered in specific gravity. The sidewall insert and bead rubber composition comprises a rubber material which comprises 20-80 wt% of a natural rubber, and 20-80 wt% of a polybutadiene rubber containing 3-35 wt% of syndiotactic 1,2-polybutadiene. Preferably the rubber material comprises further 50 wt% or less of a butadiene rubber. Preferably the composition comprises further 20-70 parts by weight of a filler; 0.5-6 parts by weight of sulfur; 0.5-4 parts by weight of a sulfenamide-based curing accelerator; and 0.5-5 parts by weight of a deterioration preventer based on 100 parts by weight of the rubber material.
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