Choosing Tire Load Index for an SUV: A Practical Guide

What the load index tells you

The load index is the two- or three-digit number in your tire's service description, printed on the sidewall after the size. Under Federal Motor Vehicle Safety Standard No. 139, load rating means the maximum load a tire is rated to carry for a given inflation pressure. The load index is a code that corresponds to that maximum load on a standardized chart. A tire with a higher index number can support more weight at a given pressure.

For an SUV, the load index matters because the vehicle is heavy and may carry passengers, cargo, or a trailer. The tire must be able to support the worst-case load on each wheel without being overloaded. Overloading a tire can cause heat buildup and failure. You can read more about the details in our explanation of tire load index ratings and the load capacity chart.

Where to find your SUV's required load index

Your SUV's door sticker, also called the vehicle placard, lists the original tire size, the cold inflation pressure, and the Gross Vehicle Weight Rating (GVWR) and Gross Axle Weight Ratings (GAWR) for the front and rear axles. It does not list the load index directly. The load index is part of the tire's service description on the sidewall. For example, a tire marked 235/65R18 104H has a load index of 104. If you still have the original equipment tires, you can read the load index from them and use that as a baseline.

If you changed tire size or want to verify the requirement, you need to calculate it from the GAWR. The owner's manual may also state the required load index for the vehicle. For a thorough breakdown of the sidewall markings, see our guide to tire sidewall markings.

How to read the door sticker

The door sticker gives you two key numbers: GVWR and GAWR. Under FMVSS 110, the sum of the maximum load ratings of the tires fitted to an axle must be at least the GAWR for that axle. On a typical SUV with two tires per axle, you divide the GAWR by two to get the minimum load capacity each tire must have. Then look up that capacity on a load index chart to find the corresponding index number.

The placard also shows the recommended cold inflation pressure. That pressure is what the tire's load capacity is based on. Using a lower pressure reduces the load capacity. Our article on vehicle load and inflation requirements explains the relationship, and tire pressure basics covers how to check pressure correctly.

Handling extra cargo

When you load your SUV with luggage, sporting gear, or passengers, the weight distribution changes. You should ensure that the total weight on each axle does not exceed the GAWR listed on the placard. If you regularly carry heavy loads, consider tires with a higher load index than the OE specification. Some SUVs come with standard-load tires; you can upgrade to extra-load (XL) tires, which are designed to operate at higher loads and higher inflation pressures than the corresponding standard tire, as defined in FMVSS 139.

For very heavy cargo or camper conversions, you may need to move to LT (light truck) tires, which have a higher load range and are built for sustained heavy use. Our article on load range for camper vans and load index for towing safety can help you decide.

Towing and load index

Towing adds significant load to your SUV, particularly to the rear axle. The tongue weight of a trailer, which is the downward force at the hitch, directly increases the load on the rear tires. You must ensure that the load on each rear tire, including tongue weight, cargo, and passengers, stays within the tire's rated capacity. The vehicle manufacturer's towing specifications will tell you the maximum trailer weight and tongue weight for your model.

If you tow near the maximum rating, the OE tires may not be sufficient. Check the load index of your current tires and compare it to the calculated requirement. If you need more capacity, choose a tire with a higher load index or an LT tire. LT tires are designed for heavier loads, and they often have a stiffer sidewall for better stability when towing. See our guide to LT tires for more on when to make the switch, and our load index for towing safety for a deeper look at the calculations.

Choosing replacement tires

When you replace tires on your SUV, match or exceed the load index of the original equipment tires. You can also use the door sticker GAWR to verify the minimum. If you upgrade to a larger wheel size, the load index may need to be higher because the tire has a smaller sidewall and less deflection. Use a load index chart to confirm the capacity.

The load index is only one of several numbers in the service description. The speed rating, load range, and construction also matter. For most SUVs, a P-metric tire with an adequate load index works well. If you drive off road or carry heavy loads, consider an all-terrain tire with a robust load range. Our SUV tire spec guide covers the basics, and you can compare all-season tires for cars and SUVs or all-terrain tires depending on your usage.

What to pick for your use

Questions

What is the difference between load index and load range?

Load index is a numeric code that tells you the maximum load a tire can carry at a given inflation pressure. Load range (such as C, D, E) indicates the ply rating and is commonly used for LT tires to show construction strength. Both affect capacity, but load index is the precise number you need for a given size and pressure.

Can I use a tire with a higher load index than the original one?

Yes, as long as it fits the rim and the vehicle. A higher load index gives you extra capacity, but it may also make the ride firmer. You should always keep the pressure within the range specified by the vehicle placard.

How do I find the GAWR for my SUV?

The GAWR is printed on the vehicle placard, usually on the driver's side door jamb. It lists the GVWR and the front and rear GAWR values.

Do I need LT tires for towing?

Not always. Many SUVs are rated to tow with their standard P-metric tires. But if the calculated load on each rear tire, including tongue weight, exceeds the OE tire's capacity, you should step up to an LT tire with a higher load range.

Does load index affect ride comfort?

Generally, a tire with a higher load index has stiffer sidewalls and can transmit more road harshness. However, choosing a tire that exceeds the requirement by a wide margin may not be necessary if you don't need the extra capacity.