What is a Trailer Tire Load Rating and What are the Differences?

What is a Trailer Tire Load Rating and What are the Differences?

A trailer tire’s load rating refers to how much load the tire is designed to carry at its industry specified pressure. Trailer tires should always be inflated to the maximum psi rating as indicated on the tire. If under inflated, a trailer tire’s side wall will build up more heat faster and cause the tire to fail. This is why trailer tires are designed to have thicker sidewalls – so that they can handle more vertical load. Passenger vehicle tires do not have as thick of a side wall as trailer tires and thus should never be used on trailers.

What are the Differences in Load Range?

All tires, including trailer tires, have load ranges. These are marked on the sidewall of the tire, and range from the lightest weight the tire can carry (load range B) to the heaviest (load range E). The load range is a measure of the maximum capacity an individual tire can carry for a boat or trailer. Most boat trailers have a load range of B, C, or D. Tires with a load range of C can carry 1,820 pounds. On a single-axle trailer, both the tires can carry a total of 3,640 pounds. This weight includes that of the trailer, boat, engine, fuel and everything else in the boat. Single-axle trailers can carry 100 percent of their load rating, but double-axle trailers require the load to be reduced by 12 percent. As load range goes up, psi goes up as well.

Here is a good chart for looking at load range and psi for ST-Metric sized special trailer service tires:

Load Range Ply Range Markings Max Load Pressure
B 4 B 35 psi (240 kPa)
C 6 C 50 psi (350 kPa)
D 8 D 65 psi (450 kPa)
E 10 E 80 psi (550 kPa)

Other Load Carrying Tips

Contact Trailer Tires Supercenter today to learn more about the best tires for your trailer.