| 摘要 |
PURPOSE:To reduce the noise level of running tires by forming a phase difference in a circumferential direction between two main grooves near the equator surface of the tire and other two main grooves near the tread ends of the tire wherein four main grooves extending in a circumferential direction are formed on the treads. CONSTITUTION:Four main grooves 3 extending in a circumferential direction are formed on the tread 2 of a pneumatic tire 1 and each groove 3 is bent in zigzag virtually with the same pitch 'P' and swing width 'W'. In this case, among the main grooves 3, a positive phase difference 'A' is formed between the main grooves 3b and 3c in a central area around a tire equator surface 4, and the remaining grooves 3a and 3d in the vicinity of tread ends 5 and 6. Said phase difference 'A' is established within a range of 1/10-1/2 of the pitch 'P' of the main grooves 3. A difference is thereby caused in treading and kicking between the edges of the main grooves 3b and 3c, and the edges of the main grooves 3a and 3d for the reduction of the noise level of the running tires. |
