Trailer tires
Load Range D or Load Range E: what the ply rating actually changes
Goodyear Endurance Trailer Tire, ST205/75R14 105N Load Range D
8 ply construction rated to a 65 psi maximum cold inflation pressure, load index 105, which is 2,039 lb per tire at that pressure.
Best for: A trailer on 14 inch wheels.
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Carlisle Radial Trail HD Trailer Tire, ST235/85R16 Load Range E
$170.99 Published ratings10 ply construction rated to an 80 psi maximum cold inflation pressure, published at 3,638 lb of load capacity per tire once fully aired up to that pressure.
Best for: A fifth wheel or a heavy equipment trailer on 16 inch wheels.
Check price on AmazonLoad range and load index get used almost interchangeably by owners shopping for trailer tires, and they measure two different things. Load Range D means 8 ply rated construction with a 65 psi maximum cold inflation ceiling; Load Range E means 10 ply rated construction with an 80 psi ceiling. The actual pounds a tire carries at that size comes from its separate load index, published on the same sidewall.
The Goodyear Endurance ST205/75R14 ships in Load Range D at load index 105, which is 2,039 lb per tire. The Carlisle Radial Trail HD ST235/85R16 ships in Load Range E, published at 3,638 lb of load capacity per tire. Comparing those two side by side is the clearest way to see what actually changes between the two ranges, and what does not.
What does Load Range actually mean?
Load range runs from B through G, and the maximum cold inflation pressure climbs with it: Load Range D tops out at 65 psi and Load Range E at 80 psi.
Published standard A published, traceable figure: a standards body, a federal regulation or a manufacturer specification states it.
| Load range | Ply rating | Maximum cold psi |
|---|---|---|
| B | 4 | 35 psi |
| C | 6 | 50 psi |
| D | 8 | 65 psi |
| E | 10 | 80 psi |
| F | 12 | 95 psi |
| G | 14 | 110 psi |
Ply rating on a modern radial is a load range equivalent carried forward from older bias ply construction, not a literal count of plies in the tire. Your own tire's sidewall states its actual load range directly.
Is Load Range the same thing as load index?
No, and confusing the two is where owners get into trouble. Load range describes the tire's construction and its maximum cold inflation ceiling. Load index is a separate published lookup table that converts a two or three digit code, stamped on the same sidewall right after the tire size, directly into a maximum load in pounds per tire. A load index of 105 means 2,039 lb, and a load index of 117 means 2,833 lb, regardless of which load range the tire happens to carry. Two tires can share the same load range and carry different load indexes depending on their specific size and construction.
What happens if a Load Range E tire is run at 65 psi instead of 80?
It carries less than its rated load, and that gap is not a small margin of safety, it is the difference between a tire that is correctly loaded and one that is not. An ST tire's published load capacity applies only at its own maximum cold sidewall pressure, so a Load Range E tire aired to 65 psi, the Load Range D ceiling, does not simply lose a little headroom, it stops being rated for the load its E designation implied it could carry. The sidewall flexes more than it was built to under that combination of load and lower pressure, generates heat, and that heat is the actual failure mechanism behind most trailer tire blowouts.
"Cold" means before the trailer has moved that day, not after a fuel stop with warm tires reading artificially high.
Which load range does a specific trailer actually need?
Work it from the axle load, not from what the trailer shipped with. Divide the loaded trailer weight, minus tongue or pin weight, across the number of tires on the ground, add a conventional reserve of roughly 15 to 20 percent for uneven side-to-side loading, and find the smallest published load index that covers the result. A published load range and load index chart shows the full table, and the site's own computed cluster page walks the same arithmetic for a specific axle weight.
Frequently asked questions
What is the difference between Load Range D and Load Range E?
Load Range D is 8 ply rated construction with a maximum cold inflation pressure of 65 psi. Load Range E is 10 ply rated with a maximum cold pressure of 80 psi. The higher load range generally carries a higher load index at a given tire size, but the actual pounds per tire is a separate published figure, not something you can read off the load range letter alone.
Is load index the same thing as load range?
No. Load range describes the tire's ply rating and its maximum cold inflation ceiling. Load index is a separate two or three digit code on the sidewall that converts directly to a maximum load in pounds per tire through a published industry table. Two tires can share a load range and carry different load indexes depending on their size and specific construction.
Can I run a Load Range D tire at 80 psi to get more capacity?
No. A tire's maximum cold pressure is a ceiling set by its own construction, and exceeding it does not raise its rated capacity, it risks a sidewall failure the tire was never built to survive. If a trailer needs the load capacity a Load Range E tire provides, the correct answer is to fit Load Range E tires, not to over-inflate a Load Range D tire past its own limit.
Does a higher load range always mean a higher load index?
Usually, but check the actual number rather than assuming it. Load range and load index are published separately for each specific tire size and model, and while a Load Range E tire typically carries more load than a Load Range D tire of the identical size, the exact figures come from the manufacturer's own published table for that tire, not from the load range letter alone.
What happens if I under-inflate an 80 psi Load Range E tire?
It no longer carries its rated load, because that rating applies only at the maximum cold sidewall pressure. Under-inflation lets the sidewall flex more than it was designed to under the same weight, which generates heat, and heat buildup is the leading cause of trailer tire tread separation and blowout, particularly at sustained highway speed.
How do I know what load range my current trailer tires are?
Read the sidewall directly. Every ST trailer tire states its load range as a letter, its ply rating, and its maximum cold inflation pressure in psi, printed alongside the tire size and load index. This is the fastest and most reliable way to confirm what is actually mounted on the trailer rather than assuming it matches what the trailer originally shipped with.
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Researched, not professional advice. This page is compiled from published standards, manufacturer towing guides and product specifications, and owner-review consensus, not hands-on testing. Figures described as a rule of thumb are towing convention rather than published standards, and they are labelled that way wherever they appear. Nothing here overrides your own ratings. Work your payload sum before your tow rating, because payload is the limit that actually binds on most half ton trucks and nearly every SUV. Load a conventional trailer to 10 to 15 percent tongue weight and a fifth wheel to 15 to 25 percent pin weight, and never lighter: a tail heavy trailer is what starts sway. Weigh the rig loaded rather than trusting a brochure dry weight. A weight distribution hitch and a set of air bags both restore ride height and control, and neither one raises a single rating. Trailer brakes are required by state law above a threshold that varies by state, and a breakaway battery that has quietly gone flat is the normal condition of most trailers on the road.