Trailer tires
ST or LT tires on a trailer: is swapping actually an upgrade?
Owners occasionally fit LT (Light Truck) tires to a trailer expecting a straightforward upgrade in toughness, and it is not that simple. ST tires exist as a separate category because a trailer axle does not steer: every turn scrubs the tire sideways across the road surface, and the ST sidewall is built stiffer specifically to resist that lateral load. An LT tire built for a steering, independently sprung axle commonly carries less capacity at the same size and the same cold pressure.
That does not make LT tires wrong for every trailer. It makes the swap a real engineering trade that has to be checked against the actual load per tire rather than assumed to be an improvement because LT tires are marketed as tougher for trucks.
Why does a trailer axle need a different tire in the first place?
A tow vehicle's tire steers, and the suspension and steering geometry are engineered to manage the sideways forces a turn produces. A trailer axle does neither: it is rigidly mounted, does not steer, and simply gets dragged sideways across the road surface every time the rig turns. That lateral scrubbing load is what an ST sidewall is specifically engineered to resist, with reinforcement most passenger, light truck and even many commercial tires were never built to handle in that direction.
The Goodyear Endurance in ST225/75R15 is a clear example: a load index of 117 for 2,833 lb per tire, built and marketed purely as trailer duty rather than as a repurposed truck tire.
What actually changes if LT tires are fitted instead?
An ST tire's sidewall is built specifically for a trailer's lateral scrub, and an LT tire of the same nominal size commonly publishes a lower load capacity at the same size and cold pressure, which has to be checked rather than assumed equal.
Published standard A published, traceable figure: a standards body, a federal regulation or a manufacturer specification states it.
| ST (Special Trailer) | LT (Light Truck) | |
|---|---|---|
| Design intent | Built for a rigid, non-steering trailer axle and the lateral scrub every turn produces | Built for a steering, independently suspended axle carrying and cornering under its own power |
| Sidewall construction | Reinforced specifically to resist sideways flex in a turn | Reinforced for load and puncture resistance, not for trailer-specific lateral scrub |
| Load at a given size and cold pressure | Rated by its own published ST load and inflation table | Commonly rated lower at the identical size and pressure; has to be checked, never assumed equal |
| Speed rating commonly published | 65 mph unless the sidewall states otherwise, with some newer ST tires rated higher | Varies by model, frequently higher than a standard ST tire, but this is a published speed rating rather than a load equivalence |
These are general published tendencies across current tire lines, not a rating for any specific tire pair. Compare the load index and maximum cold pressure printed on the actual sidewalls of the two tires under consideration.
Does an LT tire ever make sense on a trailer?
Occasionally, on trailers that spend real time on rough, unpaved or off-road surfaces where puncture resistance and sidewall flex under impact matter more than the last few percent of highway load capacity, which is why some overlanding and off-road trailer builders spec LT tires deliberately. That is a considered trade made with the actual load numbers checked, not a default swap made on the assumption that a truck tire brand name outranks a purpose-built trailer tire.
The Carlisle Radial Trail HD and the Maxxis M8008 are both ST tires stocked here because that is what the market actually sells for standard highway trailer duty. No LT trailer tire is carried in this catalog for exactly that reason: for the overwhelming majority of travel trailers, utility trailers and boat trailers, a purpose-built ST tire at the correct load range is the tire to buy.
How do you check whether a specific tire actually covers the load?
Work from the actual axle load, not the tire's category. Divide the trailer's loaded weight, minus tongue or pin weight, across the number of tires on the ground, add the conventional reserve, and compare that figure against the load index printed on the tire's own sidewall, ST or LT. A gauge rated well above 80 psi is what confirms the tire is actually at the pressure its rated load depends on, since an ST or LT tire alike only carries its rated load at maximum cold inflation.
Frequently asked questions
Can I put LT tires on my travel trailer instead of ST tires?
Physically, often yes if the size and bolt pattern match, but it is a real trade rather than a free upgrade. An LT tire of the identical nominal size commonly carries less rated load at the same cold pressure than the ST tire it replaces, and LT sidewalls were not engineered for the lateral scrubbing a non-steering trailer axle produces in every turn. Check the load index directly before swapping.
Why do trailer tires need a different design than truck tires?
Because a trailer axle does not steer. Every turn drags the tire sideways across the road surface rather than letting it roll through the turn the way a steered wheel does, and ST sidewalls are reinforced specifically to resist that lateral scrubbing load. A tire built for a steering axle, even a rugged one, was never engineered against that specific stress.
Do LT tires actually carry less weight than ST tires of the same size?
Commonly yes, at the same nominal size and the same cold inflation pressure, though the exact gap depends on the specific tires being compared. The only way to know for certain is to compare the load index and maximum cold pressure printed on each sidewall directly, since load range and load index are published per tire rather than uniform across the ST or LT category as a whole.
Are there any real advantages to LT tires on a trailer?
On trailers that see significant unpaved or off-road use, an LT tire's puncture resistance and sidewall flex under impact can be a genuine advantage over a highway-focused ST tire. This is a deliberate trade made by builders who checked the load numbers, not a general recommendation, and it does not apply to a standard travel trailer running mostly paved highway.
Why does this catalog only carry ST tires and no LT trailer tires?
Because ST tires are what the market actually sells and what nearly every travel trailer, utility trailer and boat trailer axle is designed around, so that is the honest recommendation for the overwhelming majority of readers. Naming an LT tire here without a real trailer-specific load comparison would be a guess dressed up as a rating, which this site does not publish.
Does the speed rating tell me anything about load capacity?
No, they are separate published figures. Standard ST tires carry an industry speed rating of 65 mph unless the sidewall states otherwise, and some newer ST tires and many LT tires are rated higher. A higher speed rating says nothing about how much load the tire carries at a given cold pressure, which is a completely separate number on the same sidewall.
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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.