| 摘要 |
PURPOSE:To reduce noise without deteriorating the running property on a wet road of a radial tire for heavy loads on the tread of which a plurality of longitudinal grooves extending along the circumferential direction of the tire and a plurality of ribs are provided by arranging the side walls of the longitudinal grooves in a zigzag pattern, and specifying the number of pitches of the zigzag and the depth between each mountain portion and each valley portion of the zigzag. CONSTITUTION:In a tire the tread 1 of which has a plurality of longitudinal grooves 3 provided thereon along the circumferential direction of the tire and a plurality of ribs 4 partitioned by the longitudinal grooves 3, the inclined faces of the walls 8 of the longitudinal grooves 3 are notched 7 to form a zigzag Z comprising alternate mountain and valley portions 11 and 12 in the circumferential direction of the tire. The number N of pitches of the zigzag Z in one complete turn of the tire is 200 to 700 and the depth (d) (the amplitude of the zigzag Z) between each mountain portion 11 and each valley portion 12 is set to the range of 1/2 to 1/5 of pitch length P. Thereby the resonance point of the characteristic frequency and excitation frequency of the tire is shifted out of a practical speed range toward a lower speed range so as to lower the noise level of the tire during running at high speeds. |
