Ford F-150 Tire Load Index: How to Find the Required Rating

The short answer: the door placard sets the minimum

No single tire load index applies to every F-150. Ford has fitted the truck with many tire sizes across generations, trims, wheel diameters and payload packages, and each combination has its own required rating. Start with the Tire and Loading Information placard on the driver-side door jamb. It lists the original tire size and the recommended cold inflation pressure. The load index is the two- or three-digit number after the size, usually followed by a speed rating letter. As an illustration of the format, a designation might read 275/65R18 116T, where 116 is the load index and T is the speed symbol. A replacement tire should have the same size and type, plus a load index and speed rating equal to or higher than the original specification.

The owner's manual and the sidewalls of the original equipment tires are the other two references. If the tires currently on the truck don't match the placard, trust the placard and the factory documentation. A previous owner or shop may have installed something different.

How the load index works

The load index is a code, not a weight. Each number corresponds to a maximum load a single tire can carry, taken from a standardized table. For example: • 113 corresponds to 2,535 pounds; • 116 corresponds to 2,756 pounds; • 121 corresponds to 3,197 pounds; • 123 corresponds to 3,415 pounds; One index point is a modest step. It still matters once you multiply it across four tires and add a loaded bed or a trailer tongue.

That rated capacity assumes the tire is inflated to the pressure its rating is based on. At lower inflation pressure, the same tire carries less. This is why Ford's placard pressure and the load index work together: the door-jamb pressure lets the original tires support the truck's rated loads. A tire with a higher load index doesn't deliver its full stated capacity if you run it well below the pressure that capacity requires.

What changes the required rating

Tire type is the biggest variable. Many F-150 configurations leave the factory on passenger-type P-metric tires. Some trims and packages use LT (light truck) tires, which carry a load range letter such as C, D or E and are built for higher inflation pressures. When a P-metric tire is used on a truck, its rated capacity is reduced by dividing it by 1.10. Ford's original specification accounts for this. A replacement P-metric tire must therefore meet the derated requirement, not just show a similar number. LT tires often show two load numbers, such as 121/118. The first applies to single rear wheels, which is how the F-150 is built. You can switch between P-metric and LT construction, but the load figures don't translate one-to-one, and the pressure needed for a given capacity differs.

Configuration also matters. Model year, wheel diameter, trim, cab and bed length, drivetrain, and payload or towing packages can all change the specified tire. A truck built for higher payload may call for a higher-rated tire than a base model of the same year. The certification label on the door pillar shows the gross vehicle weight rating (GVWR) and the gross axle weight ratings (GAWR). The tires must be able to support those loads.

How you use the truck affects how much margin is sensible, not the minimum. Regular towing, hauling near the GVWR, long highway runs and hot weather all add load and heat. Owners who work their trucks hard often choose LT tires for durability, but stronger tires don't raise Ford's payload or towing ratings. The same minimum logic applies to the speed rating: don't go below the placard specification. Some winter tires carry a lower speed symbol than the original tires, so check the tire maker's guidance before treating that as a straight swap.

How to check and choose replacement tires

Write down three sets of information: 1) From the door-jamb placard: the tire size, load index, speed rating and cold inflation pressure. 2) From the certification label: the GVWR and GAWR. 3) From the current tires' sidewalls: the size, load index, speed symbol, load range on LT tires, maximum inflation pressure and DOT date code. Compare the three. If the current tires fall short of the specification, correct that at the next replacement.

Use a simple axle check as a sanity test. Divide the rear GAWR by two. Each rear tire's load capacity, at the pressure you will actually run, should equal or exceed that figure. Do the same for the front axle. This check supplements Ford's tire specification; it doesn't replace it.

After installation, check cold inflation pressure with a reliable gauge at least monthly and before trips with a load or trailer. Set it to the placard value. If you changed tire size or type, use the tire manufacturer's load and inflation guidance instead. On four-wheel-drive trucks, keep all four tires the same size and model with similar tread depth. Different rolling diameters can strain the transfer case and other drivetrain parts. If one tire is damaged, follow Ford's or the tire maker's guidance on whether to replace it alone, in pairs or as a full set.

Limitations and next step

This article can't tell you the exact load index for your truck. That depends on model year and build, and the placard and Ford's build data are the authority. If the placard is missing or unreadable, a Ford dealer can look up the original tire specification by VIN. Changing tire size, fitting larger wheels or adding a lift means recalculating load capacity and inflation pressure. These changes can also affect speedometer accuracy, stability control behavior and drivetrain compatibility. A qualified tire and wheel fitment professional should confirm the setup.

Before shopping, note the placard size, load index, speed rating and pressure, along with the axle ratings. Ask the tire seller to match or exceed them for the exact tire type you choose.