Tire Load Index Ratings for Work Trucks and Equipment

A tire can have deep tread, a hard-to-find size, and the right bolt pattern, then still be the wrong tire for the job. The tire load index tells you how much weight one tire is designed to carry at its specified maximum inflation pressure. For work trucks, trailers, farm equipment, military vehicles, and industrial applications, that number is not a detail to overlook. It is a capacity limit.

A lower-priced surplus tire may be a smart buy if its size, condition, construction, and load capacity match the application. If it does not, the savings disappear fast through excessive heat, sidewall damage, unstable handling, uneven wear, or a tire failure under load.

What a Tire Load Index Means

The tire load index is a numerical code shown on the tire sidewall, usually immediately after the tire’s speed rating. On a highway tire marked 245/75R16 120/116R, for example, 120/116 are load index values and R is the speed rating. On many specialty, military, agricultural, OTR, and aircraft tires, markings can vary, and the tire may instead use a ply rating, load range, maximum load statement, or a combination of markings.

The index itself is not the weight in pounds. It is a code that corresponds to a maximum load value on a standardized load chart. A load index of 120, for example, corresponds to 3,086 pounds per tire in a single-tire application. A dual rating of 116 corresponds to 2,756 pounds per tire when the tire is used in a dual-wheel setup.

That distinction matters. Dual tires run closer together, generate more heat, and do not carry the same rated load per tire as a single tire. Do not assume that adding a second tire doubles capacity without checking the tire’s dual rating and the wheel manufacturer’s limits.

Load index, load range, and ply rating are not the same

These terms are often used interchangeably, but they describe different parts of tire capacity.

A load index is a standardized numerical capacity rating. A load range, such as Load Range E, F, G, or H, generally identifies the tire’s strength category and maximum inflation-pressure range. Ply rating is an older convention that indicates equivalent strength, not necessarily the number of physical plies in a modern radial tire.

For commercial and specialty tires, the sidewall’s maximum load and inflation-pressure statement is the working reference. A Load Range E tire is not automatically suitable for every Load Range E application. Two tires with the same load range can have different maximum loads because size, construction, and approved inflation pressure differ.

How to Read Tire Load Index Markings

Start with the full tire size and service description, not just the visible tread or outside diameter. A common LT tire marking might read LT285/75R16 126/123Q. In that example, 126 is the single-tire load index, 123 is the dual-tire load index, and Q is the speed rating.

The maximum load statement will often appear elsewhere on the sidewall. It may state a figure such as “Max Load Single 3,748 lbs at 80 psi Cold” and “Max Load Dual 3,415 lbs at 80 psi Cold.” That information is especially useful when evaluating used inventory, takeoffs, military-spec tires, or tires intended for slow-speed equipment.

On flotation sizes, bias-ply farm tires, and off-road tires, the marking may not look like a standard passenger or LT sidewall. You may see a size such as 14.00R20, 395/85R20, 18.4-38, or 26.5R25, followed by a ply rating, star rating, load range, or operating designation. The capacity is still there, but the correct chart and service conditions matter more than a quick sidewall comparison.

Calculate the Capacity Your Application Actually Needs

The correct tire is selected from the vehicle’s loaded axle weights, not from curb weight, guesswork, or what was installed when the vehicle was purchased.

For a single-rear-wheel truck, divide the heaviest expected axle load by two, then select tires with enough capacity at the inflation pressure you can safely maintain. For a dual-rear-wheel axle, divide by four, but use the tire’s dual load rating. For a trailer, account for loaded trailer weight, tongue weight, axle placement, cargo shift, and the fact that tire loading is rarely distributed perfectly.

A 10,000-pound trailer with two 5,200-pound axles is not automatically covered by four tires rated at 2,500 pounds each. Uneven loading, side-to-side cargo imbalance, rough roads, cornering, and heat can place more than an equal share on one tire. Matching the tire rating to the axle rating is a baseline. A practical margin is better, particularly for commercial hauling, gravel roads, off-road use, and long-distance highway travel.

The same principle applies to equipment. A tractor carrying a heavy front loader, a skid steer with pallet forks, or an OTR machine working on uneven ground can put substantially more load on one corner than a static weight calculation suggests. The tire must support the real duty cycle, not only the machine’s brochure weight.

Inflation Pressure Controls Carrying Capacity

A tire does not carry its full rated load at every pressure. The maximum load printed on the sidewall is tied to a stated cold inflation pressure. Running below that pressure reduces capacity and raises heat, particularly on radial truck and trailer tires.

Underinflation is one of the most common reasons a properly rated tire fails early. The sidewall flexes more, internal components run hotter, and the casing can be damaged before the outside of the tire gives a clear warning. On a loaded trailer or commercial truck, a tire that looks only slightly soft can be operating well below its required pressure.

Overinflation is not the answer. It can reduce the contact patch, worsen ride quality, increase center wear, and make an off-road vehicle more vulnerable to impact damage. Use the vehicle placard, tire manufacturer data, axle weights, and approved wheel pressure limits to establish the cold pressure. Check pressure before travel, not after the tire has heated up.

Do Not Exceed the Weakest Rating

Tire capacity is only one part of the system. The usable limit is set by the lowest-rated component: the tire, wheel, axle, hub, suspension, or vehicle rating.

Installing higher-load-index tires on a trailer with lighter axles does not increase the trailer’s legal or mechanical payload. Likewise, a heavy-duty wheel does not make an undersized tire safe. For beadlock, split-rim, multi-piece, military, and specialty wheel assemblies, confirm compatibility before mounting. Wheel width, bead-seat design, inflation limits, and hardware condition all matter.

Used tires deserve an additional inspection. Check for sidewall repairs, exposed cords, belt separation, bead damage, weather cracking, irregular wear, and previous run-flat operation. A tire can have usable tread depth and still be unsuitable for a heavy-load application. New old stock should also be inspected for storage-related cracking, casing condition, and age before entering service.

Tire Load Index for Specialty and Surplus Tires

Specialty inventory often solves fitment problems that ordinary tire stores cannot. A military tire may offer the size, traction pattern, or carcass strength needed for a restoration project, off-road build, utility truck, or equipment conversion. But military specifications do not automatically translate to modern highway service requirements.

Before buying, verify the complete size, overall diameter, section width, wheel compatibility, load markings, speed restrictions, and intended service. Some aggressive military and off-road tires are built for low-speed tactical or field use rather than sustained loaded highway miles. Some aircraft and industrial tires are designed for specific load cycles, surfaces, and operating speeds that do not match road use.

For commercial buyers, confirm whether the tire is intended for steer, drive, trailer, all-position, flotation, or non-highway service. Position matters. A tire with adequate load capacity may still be the wrong choice if its construction or tread design is not approved for that axle position.

When a Higher Load Index Makes Sense

Choosing a higher-rated tire can provide useful capacity margin, but it comes with trade-offs. Higher-capacity tires can weigh more, ride firmer, cost more, and require wheels rated for higher pressure. On lighter vehicles, an oversized heavy carcass may reduce ride comfort, braking performance, fuel economy, or steering response.

For working vehicles, trailers, and equipment, capacity margin is usually worth considering when loads vary, roads are rough, or the operation leaves little room for a roadside failure. For a lightly used recreational vehicle, the factory-specified rating may be the better fit. The correct choice depends on actual axle weights and service conditions, not the biggest number available.

Before ordering, read the sidewall, weigh the loaded equipment, and match the tire to the job it will do on its hardest day. That is the practical way to buy capacity once and avoid paying for the wrong tire twice.