Heavy-Duty Truck Tire Load Range: F, G, or H?

Understanding Load Ranges F, G, and H

Heavy-duty truck tires are marked with a letter, such as F, G, or H, that identifies their load range. This letter relates to the tire's maximum load rating at its maximum permissible inflation pressure, as defined in Federal Motor Vehicle Safety Standard No. 119. The letter does not directly state a weight number; instead, it groups tires into broad service categories. Higher letters generally indicate stronger construction and higher load capacity, but the actual pounds depend on the tire size and manufacturer specifications.

For example, a typical lineup for a commercial tire might start at F for standard over-the-road use, move to G for heavier applications, and top out at H for severe service or maximum load. However, you cannot rely on the letter alone. You must cross-reference the tire's load index, which is a number that appears in the service description, to know the exact load it can support at a given pressure. The load index rating explains this code in detail.

Federal Requirements for Heavy-Duty Trucks

For vehicles with a gross vehicle weight rating (GVWR) above 10,000 pounds, FMVSS 571.120 requires that the sum of the maximum load ratings of the tires on each axle be at least equal to the gross axle weight rating (GAWR) for that axle. This rule ensures that you do not overload a tire beyond its rated capacity. The same standard also specifies that the tires must be listed as suitable for the rims by the tire manufacturer.

The standard references FMVSS 571.119, which sets performance and marking requirements for tires used on heavy vehicles. Tires must pass endurance, strength, and high-speed tests, and they must carry the DOT symbol. When you select a tire, confirm that it meets these federal standards and that the load range letter matches your application. For guidance on how load ratings interact with vehicle weight, see Towing and Hauling.

Calculating the Load You Need per Tire

Start by reading the vehicle's certification label, which lists the GVWR and the GAWR for each axle. Divide the GAWR of the heaviest axle by the number of tires on that axle. That gives you the minimum load each tire must support. For example, a tandem axle with four tires splits its GAWR across all four, so each tire must be rated for at least one-fourth of that axle's gross rating.

Once you have that minimum, compare it with the load index of candidate tires. The load index is a code that corresponds to a specific load capacity; you can find the exact pounds in the tire manufacturer's load table. The load range letter gives you a general idea, but the load index provides the precise number. Our load capacity chart explains how to read these tables.

• Locate the vehicle certification label (driver's door jamb or owner's manual).
• Note the GAWR for the front and rear axles.
• Divide each GAWR by the number of tires on that axle.
• Choose a tire whose load index at your required inflation pressure meets or exceeds that value.
• Select a load range that offers a safety margin for severe service.

Matching Load Range to Your Service Conditions

While the legal requirement is to meet or exceed the GAWR, many fleet operators choose a higher load range than the minimum for severe service. Frequent heavy loads, long hauls, rough roads, and high ambient temperatures all increase stress on a tire. Selecting a load range one step higher, for example G instead of F, can provide a safety margin and reduce the risk of heat-related failures.

However, a higher load range often requires higher inflation pressure and may result in a firmer ride. That trade-off is acceptable for heavy-duty use, but you should not exceed the rim's rated pressure or the maximum pressure listed on the tire sidewall. Always use the vehicle manufacturer's recommended cold inflation pressure, which is found on the vehicle placard, not the maximum pressure on the sidewall. More on this in our tire pressure basics and inflation pressure chart.

Common Wheel Sizes for Heavy-Duty Trucks

Heavy-duty trucks typically use wheels in the 19.5-inch, 22.5-inch, and 24.5-inch diameter range. The load range letter is independent of wheel diameter, but larger wheels often allow bigger brakes and are common on class 8 trucks. When shopping, focus on the tire size, load range, and service description, not just the wheel size.

For a deep dive into specific commercial tire picks, see our guides for 19.5-inch tires and 24.5-inch tires. These guides compare specifications and help you match the right load range to your truck. If you run a smaller medium-duty unit, the 17.5-inch guide may also be useful.

Inspection and Maintenance Considerations

Regular inspection is critical for heavy-duty tires. Check for cuts, bulges, and uneven wear, and verify that the inflation pressure is correct. Under-inflation increases heat buildup and can lead to premature failure. According to the U.S. Department of Energy, properly inflated tires can improve fuel economy by 0.6% on average, and up to 3% in some cases, so maintaining pressure also saves fuel.

For detailed guidance on tire pressure monitoring and routine checks, see our articles on tire pressure basics and tire inspection. Also review the tire rotation schedule to extend service life and keep tread wear even.

What to pick for your use

Questions

What is the difference between load range F and G?

Load range F and G are letter designations for tire strength and load capacity. G typically indicates a higher load capacity than F, but the exact numbers depend on tire size and construction. Always check the load index and inflation pressure.

How do I know which load range my truck needs?

Check the vehicle certification label for the GVWR and axle ratings. Divide the heaviest axle's GAWR by the number of tires on that axle to find the minimum per-tire load. Then select a tire with a load range and load index that meet or exceed that value.

Is it safe to use a load range H tire when the truck only requires G?

Yes, a higher load range is generally safe, but it may require higher inflation pressure and a stiffer ride. Ensure the rim is rated for the higher pressure and that you follow the tire manufacturer's recommendations.

Can I use passenger tires on a heavy-duty truck?

No. Passenger tires are designed for vehicles with GVWR up to 10,000 pounds and do not meet the performance requirements of FMVSS 119 for heavy vehicles. Using them on a heavy-duty truck can cause overloading and dangerous failures.

Do load range letters apply to trailer tires?

Load ranges are also used on trailer tires, but trailer tires may have their own specifications. For heavy trailers, choose a load range that matches the trailer's GVWR and axle ratings, following the same calculation method.

What inflation pressure should I use for a load range G tire?

Use the vehicle manufacturer's recommended cold inflation pressure, not the maximum pressure on the tire sidewall. Higher pressures may be needed for heavier loads, but always stay within the tire and rim ratings.