Load range is a letter code — B, C, D, or E on most trailer tires — that tells you how much weight the tire can safely carry at its rated inflation pressure. Each letter corresponds to a ply rating: B is a 4-ply rating, C is 6, D is 8, and E is 10. The higher the letter, the stronger the tire. Never replace a trailer tire with a lower load range than the one your trailer came with.
What Load Range and Ply Rating Actually Mean
Decades ago, tire strength was measured by counting the actual layers of fabric — plies — built into the casing. Modern trailer tires use much stronger materials, so a tire with a 10-ply rating does not literally contain ten plies. The ply rating describes equivalent strength: the tire is built to perform as if it had that many old-style plies. Load range is simply the letter shorthand for that ply rating.
This matters more on trailers than on passenger vehicles. Special trailer (ST) tires are designed around load-carrying stiffness rather than ride comfort, and they routinely operate much closer to their maximum rated load than car tires do. If you are not sure why trailers use ST tires in the first place, our guide on ST vs. LT tires for trailers covers the differences in construction and intended use.
Load Range vs. Ply Rating: The Standard Chart
The industry uses a fixed letter-to-ply conversion. Here is how the common trailer tire load ranges line up:
| Load Range | Ply Rating | Typical Use |
|---|---|---|
| B | 4-ply rating | Small utility and light boat trailers |
| C | 6-ply rating | The most common rating on light and mid-size trailers |
| D | 8-ply rating | Heavier single- and tandem-axle trailers |
| E | 10-ply rating | Heavy equipment, cargo, and larger travel trailers |
| F | 12-ply rating | Heavy-duty and commercial trailers |
| G | 14-ply rating | The heaviest commercial trailer applications |
Keep in mind that the letter alone does not tell you the capacity in pounds. The actual maximum load depends on the tire size and is molded directly on the sidewall of every tire, along with the inflation pressure required to carry it. A higher load range achieves its extra capacity at a higher inflation pressure — the two always go together.
How to Read Load Range on the Sidewall
On the sidewall, the load range appears right after the tire size — either spelled out as "Load Range C" or abbreviated as "LRC." If you are not sure how to decode the size string itself, start with our guide to reading trailer tire sizes.
Separately, every tire carries a molded statement of its maximum load and the cold inflation pressure at which that load applies. That stamped figure — not the letter — is the number you use for capacity math. Some newer ST tires also display a numeric load index alongside the letter; when both appear, the molded maximum-load statement remains the authoritative figure for your tire.
Why You Should Never Go Down a Load Range
Replacing a Load Range D tire with a Load Range C tire of the same size reduces the weight each tire can carry, even though the two look identical from a few feet away. Trailer tires already run near their limits, and an overloaded tire builds heat — the leading cause of trailer tire blowouts. A downgraded tire may also put you below the minimum specification listed on your trailer's certification label, which can create compliance problems; check your state's requirements if you are unsure.
Going up a load range is a different story. Many owners move up one letter for extra margin, and that is generally reasonable — with two caveats. First, the extra capacity only exists at the higher inflation pressure, so your wheels must be rated for that pressure; verify the stamp on the wheel or replace it with one that matches, such as those in our trailer wheels collection. Second, a stronger tire does not raise your trailer's overall weight rating — the axles and frame still set the ceiling.
How to Calculate Total Capacity on a Tandem-Axle Trailer
The math is simple: take the maximum load molded on the sidewall of one tire and multiply it by the number of tires on the ground. A tandem-axle trailer has four tires, so its combined tire capacity is four times the single-tire rating — assuming all four tires match and are inflated to the pressure listed for that load.
Two important corrections keep that number honest. First, your real limit is the lowest of three figures: combined tire capacity, the axle ratings, and the trailer's gross vehicle weight rating. Whichever is smallest governs. Second, do not plan to run right at the limit. Weight rarely distributes evenly across four tires — cargo shifts, roads lean, and turns load the outside tires harder — so one tire can momentarily carry more than its equal share. Underinflation shrinks capacity further, which is why pressure discipline matters as much as the letter on the sidewall; our trailer tire pressure guide covers how to set and check it. And a tire that has aged or worn past its prime cannot be trusted to deliver its rated capacity at all — see our guide on when to replace trailer tires.
FAQ
Can I mix load ranges on the same trailer?
Avoid it. Mixed load ranges mean mixed stiffness and mixed pressure requirements, which unevenly distributes the load. Keep all tires on the trailer at the same load range, and never let any position fall below the rating listed on your trailer's certification label.
Does a higher load range let me haul more than my trailer's weight rating?
No. Load range only raises what the tires can carry. The trailer's gross vehicle weight rating and axle ratings are set by the manufacturer and do not change when you install stronger tires.
Do I have to run the maximum pressure printed on the sidewall?
For ST trailer tires, the general practice is yes — the tire only delivers its full rated capacity at the listed cold inflation pressure, and trailer tires are typically run at that pressure rather than adjusted downward the way passenger tires are. Confirm your wheel is rated for it.
Every trailer tire we stock ships free from our Orlando, FL warehouse — browse load ranges B through E in our trailer tires collection, or call (407) 821-7008 and we will help you match the right rating to your trailer.