| 摘要 |
PURPOSE:To improve the cracking resistance of especially a groove bottom part by disposing groove bottom rubber in the groove of cap rubber forming a tread part together with base rubber, and specifying the dynamic storage modulus of elasticity and volume percentage of each rubber and the composition and thickness of the groove bottom rubber. CONSTITUTION:A tread part 1 is formed of cap rubber 2 with grooves 4 formed therein, and base rubber 3. In this case, groove bottom rubber 5 is disposed in the groove 4, and the dynamic storage modulus of elasticity E' of the respective rubbers 2, 3, 5 is set into the relation of E'B>E'C>E'G. The volume percentage of the respective rubbers 2, 3, 5 to the whole volume of the tread part l is set into the relation of 50%<=Vc<=85%, 30%>=VB>=10% and 2O%>=VG>=5%. In the groove bottom rubber 5, 15-50 wt.parts of butadiene rubber, 2.0-5.0 wt. parts of amine group antioxidant and 1.0-4.0 wt.parts of wax are mixed in 100 wt.parts of rubber components. The thickness T of the groove bottom rubber 5 in the depth position of the groove 4 is then set to 1.0mm<=T<=3.0mm. |
