1, Chao: the difference between the two faces is small, and there are no scars, rot and bug eyes on both sides; 180 mesh double-sided polishing;
2, AA level: small front color difference; There are no 3mm scars, rot and bug eyes on both sides; 180 mesh double-sided polishing;
3. Single Grade A: No scar, rot or bug eye above 3mm on the front; Front polishing 180 mesh or more; Small defects on the reverse side, sanding above 80 mesh (some are also 180 mesh sanding);
4.AC grade: no scar above 3mm on the front, no rot, no bug eyes; Front polishing 180 mesh or more; The reverse side is polished for more than 80 meshes, and the defects are not limited;
5. Class 5.BC: there are small defects such as stuttering, black line and blue edge on the front surface, and the front surface is polished above 180 mesh; The reverse side is polished for more than 80 meshes, and the defects are not limited;
6.CC grade: double-sided quality is not limited (there may be dead knots, loose knots, rot, blue change, black lines, wormholes, skin inclusions and core pipes); C-class products are double-sided frosted with 80 meshes or more.
Note: Generally speaking, the later the letter representing the tire speed grade, the better the performance and the higher the price of this kind of tire. The application range of tires with different speed grades is also different. P-T tires (top speed 150- 190 km/h) are suitable for small and compact cars, U-V tires (top speed: 200-240-300 km/h) are suitable for middle and high-class cars, and W-Z tires with the best performance are suitable for middle and high-class cars, because their top speed is 240.
Tires are mainly made of polymer composite materials, and the increase of temperature will accelerate the aging of rubber. When the car is driving at high speed, the temperature of the whole tire will rise, which will lead to increased tread wear. Every tire has its designed critical speed. When the high speed reaches this speed, the tire will appear "standing wave" phenomenon, which is the "critical speed" of the tire.
If you continue to use it in this situation, the tire will be in danger of puncture. So drive safely and don't overspeed. For example, the speed class W in the above figure, compared with the table, the maximum speed is 270 km/h.