How to Compare Tire Dimensions

Comparing the dimensions, or sizes, of tires is not a difficult task to do, especially once you fully understand the markings on the sidewalls. It is important, however, to keep in mind that there is more to consider when purchasing tires than the sizes and dimensions.

1. Inspect the sidewalls of your tires and take down a series of numbers that resembles “LT235/75R16 84H”. The “LT” stands for light trucks and simply means that the tires were designed for these types of vehicles. On the other hand, if there is a “P” in place of the “LT”, this means the tires were designed for passenger vehicles. The number behind this letter is the section width, or the tread width of the tire. It is a measurement that is taken in millimeters and in this case, the measurement is 235mm.


2. Compare the next number, “75”, which is the aspect ratio of the tires. This measurement is the percentage of the tire’s width versus the height above the rim. This is perhaps the most difficult dimension to understand. For instance, this tire is 235mm wide and since there is the number “75”, this means the height above the tire’s rim is equal to 75 percent of the tire’s width, which equals 176.25 mm. The lower the number, the better handle the tire has, but also the rougher the ride.


3. Look at the letter behind the aspect ratio. The “R” indicates this tire is of radial ply bias. Other options may include a “D” for diagonal ply bias, or “B” for belted ply bias.


4. Look at the number behind the ply bias. The number “16” is the rim’s diameter in inches. When comparing dimensions, this number must stay the same on any replacement tires unless, you plan to replace the wheel, as well.


5. Determine the load rating by looking at the number behind the diameter. The “84” is the load rating, which indicates the ability the tires have to carry large loads. The higher the number, the larger the tires can hold. This rating is close to the car’s weight, in addition to the anticipated weight of the cargo, or passengers.


6. Analyze the speed rating of the tire with the final letter. The final letter, “H”, indicates to tire’s speed rating. “H” is equal to 130 mph, while other ratings such as “S” or “V” equal 112 mph or 149 mph, respectively.