01/22/2026
Trailer Tire Load Range & Ply Rating
Trailer tire load range and ply rating (PR) describe how much weight a trailer tire can safely carry and the air pressure required to support that load. These ratings apply to ST (Special Trailer) and commercial trailer tires, not passenger or light truck tires.
What Is Trailer Tire Load Range?
Trailer tire load range identifies the maximum load capacity of a trailer tire at a specific maximum cold inflation pressure. The load range is shown as a letter on the tire sidewall, such as B, C, D, E, F, G, H, J, or L.
Higher load range letters mean:
Higher weight capacity
Higher maximum PSI
Stronger tire construction
Trailer tires are designed to operate at their maximum rated PSI, which is molded on the tire sidewall.
What Is Ply Rating (PR)?
Ply rating (PR) is a standardized strength rating, not the actual number of plies inside a modern trailer tire. It represents the tire’s ability to carry weight and resist heat and sidewall flex.
Examples:
Load Range C = 6 Ply Rating
Load Range D = 8 Ply Rating
Load Range E = 10 Ply Rating
A higher ply rating means greater load-carrying strength and durability.
Why Load Range Matters for Trailer Tires
Using the correct trailer tire load range helps:
Prevent tire blowouts
Reduce heat buildup
Improve trailer stability
Extend tire lifespan
Maintain DOT and FMCSA compliance
Most trailer tire failures are caused by under-rated load range or incorrect inflation pressure.
ST Trailer Tires vs Passenger and LT Tires
Load range and ply rating standards apply only to trailer tires marked ST or commercial trailer tires.
Passenger (SL / XL) and Light Truck (LT) tires are not designed for trailer use and should not be used on trailers.
How to Choose the Correct Trailer Tire Load Range
To select the correct trailer tire:
Find the trailer’s Gross Axle Weight Rating (GAWR)
Divide the axle weight by the number of tires
Choose a trailer tire with a load range that exceeds the required load per tire
Inflate the tire to the maximum cold PSI on the sidewall
Confirm wheels and valve stems are rated for the tire’s PSI
Key Takeaway
Trailer tire load range and ply rating determine how much weight a trailer tire can safely carry and the air pressure required for safe operation. Choosing the correct load range improves safety, towing stability, and tire longevity. Always use ST-rated trailer tires and follow the tire manufacturer’s sidewall specifications.
