| 摘要 |
<p>A pneumatic tyre comprises a tread portion (2) provided with a series of design-cycles repeating in the circumference of the tyre at variable pitches (L), wherein the number (NP) of different kinds of pitches is at least 10. The variable pitches (L) repeatedly increase and decrease alternately in one circumferential direction of the tyre to define start design-cycles from which the pitches (L) start to increase. A series of design-cycles is composed of a series of units (U), each unit (U) being defined as a group of design-cycles starting from and including one of the start design-cycles to but excluding the next start-cycle. The total number (NU) of the units is from 4 to 20. The units consists of at least one first-unit the number of which is 20 to 80% of the total number, at least one second-unit the number of which is 20 to 80% of the total number, and optionally a third-unit the number of which is 0 to 60% of the total number. The first unit is defined as including at least one pitch which is not less than a standard long pitch (PLa) and at least one pitch which is not more than a standard short pitch (PSa). The second unit is defined as including at least one pitch within one of the following two ranges, a range of not less than the standard long pitch (PLa) and a range of not more than the standard short pitch (PSa), but no pitch within the other range. The third unit is defined as all the pitches therein are more than the standard short pitch (PSa) and less than the standard long pitch (PLa). The standard long pitch (PLa) is the maximum pitch (PL) minus a length of 0.2 times a maximum pitch difference (MPD). The standard short pitch (PSa) is the minimum pitch (PS) plus a length of 0.2 times the maximum pitch difference (MPD), and the maximum pitch difference (MPD) is the maximum pitch (PL) minus the minimum pitch (PS). <IMAGE></p> |
