Tire Load Index 93 vs 97: Capacity Compared

What tire load index numbers mean

The load index is a numeric code molded into the tire's sidewall as part of the service description, such as the "97" in a size like 235/55R18 97H. It corresponds to a specific maximum load capacity defined by industry standards. Federal regulations define "load rating" as the maximum load a tire is rated to carry for a given inflation pressure, and each tire's maximum load rating is marked on its sidewall. See how to read tire load index ratings and tire sidewall markings for a deeper look.

The load index is not a weight measurement by itself; it is a code that must be interpreted using a standard load index table. The table, maintained by organizations such as the Tire and Rim Association and ETRTO, assigns a weight capacity to each index number. The key point is that higher numbers indicate a higher load capacity. Load index 97 always corresponds to a greater load capacity than load index 93, regardless of the tire size. Additionally, the load rating also depends on inflation pressure: as pressure increases, the load rating can increase up to the maximum permissible inflation pressure, as defined in Standard No. 139.

Load index 93 vs 97: what the difference means

Load index 93 and load index 97 are both common on passenger vehicles, but the difference in load capacity is significant enough to matter for many real-world applications. A tire with a 97 index can support a larger load than one with a 93 index, though the exact difference in pounds depends on the tire's size and the inflation pressure you use. This means that a 97 tire may be necessary for a heavier SUV or a vehicle that often carries five passengers plus luggage.

The choice between 93 and 97 is primarily driven by the vehicle's gross axle weight rating (GAWR). Federal regulations require that the sum of the maximum load ratings of the tires on an axle be at least equal to the GAWR. For vehicles with a GVWR of 10,000 pounds or less, this requirement is found in 49 CFR 571.110; for heavier vehicles, it appears in 49 CFR 571.120. Therefore, if your vehicle's GAWR is high, you need tires with a high enough load index to cover it. Load index 97 provides more margin than 93 for the same axle load.

A higher load index also indicates a tire designed for heavier-duty service. Such tires often have reinforced sidewalls or an extra load designation, which helps them handle the added stress of heavier loads without excessive flex or heat buildup. This is why many light trucks and full-size SUVs come from the factory with load index 97 or higher.

How to find the load index your vehicle needs

The first place to look is the vehicle's tire placard, usually located on the driver's side door jamb. It lists the original tire size, including the load index and speed rating. It also gives the recommended cold inflation pressure. The placard is part of the vehicle's certification information and is authoritative for the original equipment tires.

You can also check the certification label, which shows the GAWR for each axle. Federal standards require that tires be selected so that the sum of the maximum load ratings on an axle is at least the GAWR. For multipurpose vehicles and trucks under 10,000 pounds, the load rating of a passenger car tire must be reduced by dividing by 1.10 when calculating that sum, per 49 CFR 571.120. This reduction is important when considering aftermarket tires.

If you are replacing tires with a different size, the new tire's load index must meet or exceed the original specification. Going from a 93 to a 97 is generally acceptable if the tire fits the wheel and the speed rating is compatible, but going from a 97 to a 93 is not safe. Use a tire load capacity chart to verify the actual capacities at the recommended pressure; see how to read a tire load capacity chart.

Vehicle selection and load index

Vehicle manufacturers choose the load index based on the vehicle's weight, payload, and intended use. Lighter cars often use load index 89 to 93, while heavier crossovers, SUVs, and light trucks may require 95 to 100 or higher. If you are shopping for new tires, knowing which load index your vehicle needs is the first step. The best car and SUV tires guide can help you match tires to your vehicle's specifications.

The load index also matters when you modify a vehicle, such as adding a lift kit or a towing package. Heavy loads increase the load on each tire, so a higher load index like 97 provides extra capacity and a safety margin. Tires with a higher load index are often built with stiffer sidewalls and more robust construction, which is why many light truck owners choose aftermarket tires with an index higher than the factory requirement. For trucks and vans, see the best light truck tires guide.

Inflation pressure and load rating

A tire's load rating is only valid at the inflation pressure you use. Federal regulations define "maximum load rating" as the load rating at the maximum permissible inflation pressure, which is typically much higher than the vehicle's recommended pressure. For example, a tire might have a maximum load rating at 44 psi, but your vehicle's placard might call for 32 psi. The actual load capacity at 32 psi is lower, so you must not exceed the load rating corresponding to that pressure.

The load index is based on the tire's standard pressure, but you should always follow the vehicle manufacturer's recommended pressure, not the tire's maximum. Underinflation reduces load capacity and can cause overheating. The Tire Pressure Monitoring System standard, 49 CFR 571.138, requires a warning when pressure drops 25 percent below the recommended value, highlighting how critical correct inflation is. For more on setting pressures, see tire inflation basics.

What to pick for your use

Questions

Can I use a load index 97 tire on a vehicle that originally had 93?

Yes, as long as the tire fits the wheel and the speed rating is compatible. The higher load index only adds capacity. The tire's dimensions must also match the vehicle's rim and clearance.

What happens if I install a tire with a lower load index than the vehicle requires?

The tire will be overloaded, leading to excessive heat, rapid wear, and potential failure. It also violates federal safety standards, which require the sum of axle load ratings to be at least the GAWR.

Does a higher load index affect ride quality?

It can. Tires with a higher load index often have stiffer sidewalls to support more weight, which may make for a firmer ride. However, the effect is often subtle and depends on the tire's overall construction and inflation.

How do I know the exact load capacity of a load index 93 or 97 tire?

The exact capacity is listed in the load index table published by tire standards organizations. You can also check the tire's sidewall, which shows the maximum load rating at the maximum inflation pressure. Always compare this to your vehicle's GAWR.

Is load index the same as load range?

No. Load range (like SL or XL) indicates the tire's ply rating and maximum pressure. Load index is a numeric code that, combined with the speed rating, forms the service description. Both are important for selecting the right tire.