Tire Load Index: What It Means and How to Choose Yours

What Is the Tire Load Index?

The tire load index is a numerical code printed on the sidewall that tells you the maximum load a single tire can support when properly inflated. The higher the number, the greater the load capacity. The index works together with inflation pressure: the load rating is the maximum load a tire is rated to carry for a given inflation pressure, as defined in federal safety standards.

The load index appears as part of the tire's service description, which includes a number for load and a letter for speed. You will find it after the wheel diameter, such as in a size like P225/60R16 followed by a two- or three-digit number and a letter. The letter indicates the speed rating, which our guide to tire speed ratings explains in more detail.

How to Read the Load Index on Your Sidewall

Look at the sidewall of your tire. After the tire size, which includes width, aspect ratio, and wheel diameter, you will see a combination like 98H. The number 98 is the load index, and the letter H is the speed rating. This pair is called the service description.

Federal regulations require that the maximum load rating be marked on the tire sidewall, along with the inflation pressure. The load index itself is a code that corresponds to that maximum load rating. Some tires also carry a load range letter, an older system used mainly on light truck and trailer tires. Our article on tire load range covers that distinction.

Load Index vs. Load Range

While the load index is a numerical code for a specific weight, the load range is an older letter-based system used primarily on light truck and trailer tires. Load range letters indicate ply rating and reinforced construction, affecting capacity and required inflation pressure.

The federal standard for light vehicles defines an extra load tire as one designed to operate at higher loads and higher inflation pressure than a standard tire. If a tire is marked XL or Extra Load, its load index already accounts for that higher capacity. When comparing tires, the load index is the more precise way to match load capacity.

How to Choose the Right Load Index

The safest approach is to replace your tires with the same size and load index that came on the vehicle. You can find this information on the vehicle placard, usually located on the driver's side door jamb or inside the fuel door. The placard also lists the recommended cold inflation pressure.

Federal safety standards require that the vehicle maximum load on a tire not exceed the maximum load rating marked on the sidewall. For multipurpose passenger vehicles and trucks, the sum of the maximum load ratings of the tires fitted to an axle must be at least equal to the gross axle weight rating (GAWR) for that axle. So your tires must collectively meet or exceed that rating.

If you are considering a different tire size, such as upsizing the wheel diameter, you may need a higher load index to maintain the same load capacity. Our guide to tire plus sizing explains how to adjust the load index when changing sizes.

The load index is part of the tire's service description, which also includes the speed rating. Both must be considered when selecting replacement tires. While the speed rating affects the tire's maximum service speed, the load index ensures the tire can support the vehicle's weight.

Special Considerations for Light Trucks, Trailers, and Heavy Loads

For light trucks and SUVs that carry heavy loads, you may need a tire with a higher load index than the standard passenger car version. Federal standards for tires used on vehicles over 10,000 pounds GVWR impose different requirements, and light truck tires have their own markings.

Trailers are another special case: trailer tires are designed to handle the specific loads of towed vehicles. Using a tire with an insufficient load index can lead to overheating and failure. Always use tires with a load rating appropriate for the loaded trailer weight, and consult our best trailer tires guide for options.

If you frequently carry heavy loads or tow, consider upgrading to a higher load range or an extra load tire. Check the load index carefully, as it is the direct measure of capacity. For light trucks, our best light truck tires guide can help you find suitable models.

Common Mistakes with Load Index

One common mistake is assuming that all tires of the same physical size have the same load index. In fact, different models can have different load indices even in the same tire dimension, so always verify the number.

Another error is ignoring the load index when replacing only two tires. If you mix tires with different load indices on the same axle, the lower-rated tire becomes the weak point. It is best to replace tires in sets or at least match them on an axle to maintain balanced capacity.

What to pick for your use

Questions

What does the load index number mean?

The load index is a code that corresponds to the maximum load a tire can carry at a specified inflation pressure. Higher numbers mean higher capacity. The exact weight values are published by tire standards organizations, and the maximum load rating is marked on the tire.

Where do I find the recommended load index for my vehicle?

Check the tire information placard on the driver's side door jamb or inside the fuel door. It lists the original tire size, load index, speed rating, and recommended cold inflation pressure.

Can I install a tire with a higher load index than stock?

Yes, as long as the tire is the correct size and fits your vehicle. A higher load index provides extra capacity, but you should still follow the pressure recommendations on the placard.

What happens if I use a tire with a lower load index?

The tire may be overloaded, leading to excessive heat, premature wear, and possible failure. Federal safety standards require that the vehicle's loads not exceed the tire's maximum load rating.