What do the speed letters on car tires represent?
2 Answers
The letters JKLMNPQRSTUHVWYZ correspond to the speed ratings of radial tires. Among them, J to Y represent speeds of 100, 110, 120, 130, 140, 150, 160, 170, 180, 190, 200, 210, 240, 270, and 300 kilometers per hour, while Z represents speeds above 240 kilometers per hour. The speed rating letters on tires indicate the maximum speed at which the tire can carry a specified load under defined conditions. Meaning of speed ratings: Tires with different speed ratings have varying applications. P—T rated tires (maximum speed 150—190 km/h) are suitable for small and compact cars, U—V rated tires (maximum speed 200—240 km/h) are suitable for mid-to-high-end sedans, while the highest-performing W—Z tires, which can withstand speeds between 240—300 km/h, are typically used for large luxury cars and supercars. Higher-grade tires are not only superior in terms of maximum speed (under load conditions). It's important to note that tires generate heat due to compression and deformation when rolling at high speeds, so higher-grade tires naturally have better resistance. To achieve this effect, enhancements are made to the tire shoulders and tread patterns to reduce the likelihood of deformation, and the wet grip performance of the tires is also improved. Therefore, it's essential to pay extra attention to tire maintenance. In daily use, the following points should be noted for tire care: Regularly inspect the tire surface for cracks, deformations, or other defects. Due to wear from driving, the tread grooves gradually become shallower. If the tread is worn flat, it loses its ability to drain water and provide anti-slip functionality, significantly reducing the car's performance. Tiny cracks may seem insignificant but can pose a risk of tire blowouts at high speeds. Additionally, promptly remove small stones lodged in the grooves. Park the car on flat ground whenever possible. Avoid parking on roads with thick, sharp, or pointed stones. Do not park the car near or in contact with petroleum products, acids, or other materials that can degrade rubber. After parking, the driver should avoid turning the steering wheel, as this can accelerate tire wear. Do not splash water to cool overheated tires. In hot weather or during high-speed driving, tires can overheat, and the internal pressure may increase. In such cases, stop to let the tires cool naturally. Never release air to reduce pressure or splash water to cool the tires, as this can cause abnormal aging of the tread rubber. Avoid sudden braking. Minimize frequent use of brakes and emergency stops to prevent accelerated tread wear caused by dragging between the tires and the ground.
I've been driving for over a decade. The speed letter on tires actually indicates the tire's maximum safe speed, for example, H represents 210 kilometers per hour. This letter can usually be found in a string of codes on the sidewall of the tire. You can't just randomly choose tires, otherwise they might burst or wear out quickly on highways. A friend of mine once chose the wrong tire model because of this, and later lost control on the highway—fortunately, nothing serious happened. Now, whenever I go to the repair shop to change tires, I always remind them to check if this letter matches my driving habits. For city commuting, a T-rated tire with 190 km/h is sufficient. But if you often drive long distances or enjoy speeding, something like an H or V-rated tire is better, ensuring both safety and tire longevity. Remember, don't just look at the brand; the speed rating is also crucial—it's directly related to driving safety. During regular maintenance, take the time to check your tire condition to avoid many unexpected incidents.
