Your tires are the contact point between the vehicle and the road, so it should be no surprise that they should be cared for properly. Some people think that replacing them in a timely manner is enough and while that is correct, it’s much more than that.
Caring and replacing your tires would be a lot easier once you understand what the label means. To explain the figure, we used the Suzuki Celerio’s tire specs.
165 / 65 R14 79S
The number 165, refers to the width of the tire from sidewall to sidewall. It’s measured in millimeters, which you can divide by 25.4 if you want the figure in inches. In this case, the tire’s width is 6.50-inches.
65 is the height of the sidewall from the edge of the rim to the tread or surface. Unlike the width, the figure for the height is a ratio and not a direct measurement. For this, it means the height is 65% of the width, that is 165 x .65 = 107.25 mm or 4.22-inches.
R means radial, the most popular construction method used in tires nowadays. Another kind would be ‘D’ referring to diagonal manufacturing, commonly used for light trucks and spare tire applications.
After this is 14 or the size of the rim allowed inside the tire, measured in inches.
Load Index and Speed Rating
79 is the tire’s load index, telling us approximately how much the tire can carry when fully inflated. It has a corresponding weight in the load index chart, with 79 able to support up to 437 kg. In buying a new tire, it is recommended that you buy one with the same load index or higher to ensure your vehicle can be safely supported.
The letter beside the load index is the Speed Rating, an indication of how fast the tire can go safely. S tires are rated to go up to 180 km/h. Another sample would be ‘V,’ rated to last up to 240 km/h. If there’s a manufacturer indication of a lower speed limit for the tire, you should follow that.
Spare Tire Sample
The wheel above is a spare from the same Suzuki Celerio we used as an example earlier. The letter before the width of the tire refers to the application it is meant for. T means it should be a temporary wheel only. Should you use it, you must have your main tire fixed as soon as possible. Other application indications would be P for passenger, and LT for Light Trucks.
As a review, you would see that the spare tire is 105 mm in width or 4.13-inches. The sidewall height is 70% of the width, that’s 105 x .70 = 73.5mm or 2.89 inches. The tire has a diagonal construction, a load index of 84 making it able to carry 500 kg, and an M rating that makes it safe to run up to 130 km/h. However, the sticker on the rim says it should only run up to 50 mph or 81 km/h and this should be followed.
It is worth understanding what these numbers and letters mean to better know how it will affect your car. Remember to keep your tires at the manufacturer’s suggested tire pressure and have their camber alignment checked regularly to help maintain its optimum performance.