What Is Tire Load Index And Why Is It Important To Know?

Though many people recognize tire measurements, not everyone knows how to read the symbols on their sidewalls. Getting a grasp of how to read this is crucial to better understanding the tires you currently own as well as any you may purchase in the future. One important piece of a tire's components is the tire index.

In short, the tire index is a number that pinpoints the weight capacity your tire can support when at full air pressure, an important tire detail to know. This is typically represented by a two or three digit number located at the end of the tire's sidewall information, positioned to the left of the load range, or speed index. However, the number itself is not the actual amount of weight your tire can carry. Rather, it is a numerical representation of the maximum weight, which can be translated on a tire load index chart. For example, in the image above, the tire index is 92 while the load range is W, which means it can carry 1,389 pounds at up to 168 MPH.

Perhaps the most obvious benefit to knowing your tire's load index is it will help you better understand your vehicle's loading limits, preventing blowouts and further damage. Furthermore, it's important to know your tires' load index when replacing them with new ones. Just as you shouldn't have two different-sized tires on your car, it's unwise to have new tires with lower original load index ratings, as they will struggle to support the weight of your vehicle, passengers, and belongings. New tires with higher load index ratings can be used, so long as other specifications such as speed rating and size are a match. 

So now that you know why your tire's load index is so important, how do you actually go about deciphering it? As mentioned previously, the number on your tire corresponds with how much weight it can support, which can be found on a load index chart. While it's best to consult your manual or manufacturer to get the specifics on how it translates for your car, the chart is generally the same for most typical passenger vehicles. 

For most standard cars and light trucks, you'll find tire load index ratings between 70 and 124. From there, the weight capacity can range from 739 to 3,527 pounds. In less typical cases you may also come across load index ratings as low as one with a weight capacity of 102 pounds and others as high as 150 with weight capacities exceeding 7,300 pounds. 

However, this number won't indicate the total maximum load capacity of your car as a whole, rather only acting as a rating for each individual tire. To know how much your car's tires can support in total, you simply have to multiple the amount of pounds by four. For example, if your car has a load index of 70 and is rated to support 739 pounds, you would multiply 739 by four and get 2,956 pounds.