| 摘要 |
PROBLEM TO BE SOLVED: To prevent generation of idle rotation by enhancing the resistance against rim slip, longitudinal and crosswise rigidity, and ensuring that bead wires installed in a base part have good resistance against the rim slip. SOLUTION: A base rubber is composed of natural rubber, SBR containing 20-50W/W% stylene, phenol resin in an amount of 5-15% (PHR) of the total content of natural rubber and SBR, and hexamethylene-tetramine as a hardening agent for phenol resin, wherein the ratio by weight of SBR to natural rubber ranges from 2:8 to 7:3. The JISA sprung hardness of the base rubber (JISK 6301<-1975> ) should be over 85 while the modulus of elasticity at the 100% elongation be 5-12MPa, wherein the tread rubber consists of natural rubber and SBR, and the JIS-A spring hardness of the tread part (JISK 6301<-1975> ) ranges from 50 to 65, and the modulus of tensile elasticity at 100% elongation is between 3 and 7MPa, and a plurality of bead wires wound round in the circumferential direction are installed in the base part. |
