Load Range Chart for Trailer Tires: What the Ratings Mean and Why They Matter
Trailer tires carry loads differently than passenger car tires, and choosing the wrong load range can lead to blowouts, swaying, or structural failure — especially at highway speeds with a fully loaded trailer. Understanding the load range system helps you read specifications accurately and verify that your tires are rated for what you're asking them to do.
What Load Range Means
Load range is a letter-based rating system that tells you how much air pressure a tire can safely hold and, by extension, how much weight it can support. It replaced an older ply-rating system — though you'll still see "ply rating" used in casual conversation. Higher load range letters indicate stronger tire construction with more internal layers and higher maximum inflation pressure.
The rating is stamped on the tire sidewall, often following the tire size (for example: ST225/75R15 Load Range E).
Trailer Tire Load Range Chart
| Load Range | Ply Rating | Max PSI (typical) | Typical Use |
|---|---|---|---|
| B | 4-ply | 35 psi | Light-duty utility trailers |
| C | 6-ply | 50 psi | Small boat trailers, light cargo |
| D | 8-ply | 65 psi | Medium cargo, enclosed trailers |
| E | 10-ply | 80 psi | Heavy-duty travel trailers, large loads |
| F | 12-ply | 95 psi | Very heavy commercial and specialty trailers |
| G | 14-ply | 110 psi | Heavy commercial hauling |
Maximum PSI figures are typical industry values and vary by manufacturer and tire size. Always verify the specific tire's sidewall markings.
How Load Capacity Works With Tire Pressure
Load range and inflation pressure work together — you don't get the full load capacity without inflating the tire to its rated maximum. Running an E-rated tire at 60 psi instead of 80 psi doesn't give you E-rated capacity; it gives you something less. This is a common mistake that contributes to overloading without obvious warning signs. 🚨
Each tire has a maximum load rating listed in pounds on the sidewall. The total load capacity of your trailer axle equals that number multiplied by the number of tires on that axle. If your loaded trailer exceeds that total, you're overloaded regardless of what the load range letter says.
ST vs. LT Tires: Why Trailer Tires Are Different
Tires marked ST (Special Trailer) are built specifically for trailer use. They have stiffer sidewalls than passenger or light truck tires, which helps control trailer sway and supports vertical loads without flexing as much side to side.
LT (Light Truck) tires also use letter-based load ranges but are engineered for powered axles — braking, acceleration, and cornering forces that trailer tires don't experience. Using LT or passenger tires on a trailer is generally not recommended by manufacturers because the sidewall dynamics are different.
The ST designation matters when reading a load range chart: the same load range letter on an ST tire and an LT tire reflects different engineering assumptions.
What Affects Which Load Range You Need
No chart alone tells you the right load range for your setup. Several factors shape the correct answer:
- Gross Vehicle Weight Rating (GVWR) of your trailer — the total maximum loaded weight the trailer is designed to carry, including cargo
- Number of axles and tires — more tires distribute the load, so the per-tire requirement changes
- Tongue weight and load distribution — uneven loading increases stress on specific tires
- Towing speed and distance — trailer tires build heat under sustained highway speeds; higher load ranges handle heat better
- Tire size — two tires with the same load range letter but different sizes will have different maximum load capacities in pounds
- Trailer type — travel trailers, flatbeds, enclosed cargo, boat trailers, and horse trailers each put different demands on tires
Reading the Sidewall 🔍
A trailer tire sidewall contains everything you need to cross-reference with a load range chart:
- Size designation (e.g., ST235/80R16)
- Load range letter (e.g., LR E)
- Maximum load in pounds (and sometimes kilograms)
- Maximum cold inflation pressure in psi
- DOT code with manufacturing date
"Cold inflation" means the pressure measured before the tire has been driven on that day. Trailer tires should always be checked cold, before the trailer moves.
When Load Range Becomes a Safety Issue
Overloading a tire — even briefly — generates internal heat that weakens the structure permanently. A tire that's been overloaded may look fine on the outside but fail miles later. Load range ratings aren't conservative estimates with wide margins; they're engineering limits.
Equally important: don't assume a higher load range is always better without checking the wheel rating. Wheels have their own load ratings, and putting a higher-pressure tire on a wheel not designed for it creates a different problem.
The Variables That Determine Your Specific Answer
Matching a load range to your trailer requires knowing your trailer's actual GVWR, the number and size of tires it runs, how you load it, and how you use it. A utility trailer used occasionally for light loads operates in a completely different range than a travel trailer towed cross-country at gross weight.
The chart gives you the framework. Your trailer's documentation, the tire sidewall, and the axle rating together tell you whether the numbers actually align.
