What do the numbers and the letter W on tires mean?
4 Answers
Tire numbers sequentially represent the tire's section width, aspect ratio, tire type code, rim diameter, load index, and speed rating. The letter W on a tire indicates its speed rating, with W corresponding to a speed rating of 270 kilometers per hour. Tire specifications are commonly represented by a set of numbers, where the first number indicates the tire's section width and the second number indicates the rim diameter, both measured in inches. Taking 215/60R1795H as an example, 215 refers to the tire width of 215mm, 60 refers to the aspect ratio, R indicates a radial tire, 17 means the tire diameter is 17 inches, 95 represents the load index, and H is the speed rating.
As a seasoned driver with 15 years of experience, I often help friends understand tire markings. The numbers and letters, such as 215/65R15 W, represent the tire's size and performance parameters. 215 is the tire width in millimeters, 65 is the aspect ratio, meaning the height is 65% of the width, R indicates a radial structure for better durability, and 15 is the rim diameter in inches. W stands for the speed rating, representing a maximum speed of 270 kilometers per hour. Choosing the wrong speed rating, like using low-speed tires for high-speed driving, can cause the tires to overheat and burst, which is extremely dangerous. When replacing tires, always refer to the vehicle manual to match the specifications, otherwise, handling and fuel consumption will be affected. Regularly checking tire wear and pressure can prevent failures. I perform a self-check every six months to ensure safety and peace of mind.
From my safety-focused experience, the numbers on tires like 205/55R16 W are crucial. The W indicates a speed rating of 270km/h, but the actual suitability depends on the vehicle condition—higher isn't always better. Other numbers are size codes; for example, the 205mm width affects grip. Accidentally using tires with the wrong speed rating can lead to imbalance at high speeds, potentially causing loss of control and accidents. I recommend taking photos of the old tire codes during each maintenance session to compare with new tires, avoiding incorrect installation. Checking tire pressure and wear can extend their lifespan—small oversights here can pose significant risks.
After years of modifying cars, I've mastered tire codes. Take 215/65R15 W for example - the W simply indicates a speed rating of 270. Don't randomly change this when selecting tires. The size numbers affect performance; for instance, higher aspect ratios improve comfort but weaken handling. Matching OEM specifications is the safest choice, otherwise you'll face increased fuel consumption and softer braking.
