ST (Special Trailer) tires and LT (Light Truck) tires are built for different jobs. ST tires have stiffer, heavier sidewalls designed to carry weight and resist sway on free-rolling trailer axles. LT tires are engineered for trucks that steer, drive, and corner. For most trailers, an ST tire is the correct choice; LT tires are sometimes used on heavy trailers, but that swap has trade-offs worth understanding.
What ST and LT Actually Mean
The letters at the front of a tire size tell you what the tire was designed to do. ST stands for Special Trailer: a tire built exclusively for trailer axles, which never steer, never receive engine power, and spend much of their life parked. LT stands for Light Truck: a tire built for pickups, vans, and SUVs that need traction for acceleration, braking, and cornering under load.
You will also see P (passenger) tires on the road, and those do not belong on a trailer at all — we cover the reasons in our guide on why car tires should never go on a trailer. If the rest of the sidewall markings look like alphabet soup, our trailer tire size guide walks through every number and letter.
Sidewall Construction: Where the Two Designs Split
The biggest engineering difference between ST and LT tires is in the sidewall. An ST tire uses a stiffer, more heavily reinforced sidewall than a comparable LT tire. That stiffness does two things on a trailer:
- Carries more weight for a given size. Because an ST tire does not need to flex for cornering grip or ride comfort, its casing can be dedicated to load capacity. A same-size ST tire generally carries more weight than its LT counterpart.
- Resists trailer sway. A trailer is hinged to your tow vehicle, and soft sidewalls let it wander side to side. Stiff ST sidewalls keep the trailer tracking in a straighter line behind you.
ST tires also tend to use shallower, simpler tread patterns — a free-rolling axle does not need aggressive traction blocks — and rubber compounds formulated to hold up against UV exposure and weathering, since trailers often sit unused for long stretches. LT tires make the opposite trade: more flexible sidewalls for ride and grip, deeper tread for traction, and compounds tuned for the heat of daily driving.
ST vs LT: Side-by-Side Comparison
| Feature | ST (Special Trailer) | LT (Light Truck) |
|---|---|---|
| Designed for | Free-rolling trailer axles only | Drive, steer, and braking axles on trucks and SUVs |
| Sidewall | Stiff, heavily reinforced; resists sway and flex | More flexible; tuned for cornering grip and ride quality |
| Load capacity (same size) | Higher — casing is dedicated to carrying weight | Lower than a comparable ST tire |
| Tread | Shallower, simpler pattern; low rolling resistance | Deeper tread for traction in acceleration and braking |
| Compound priorities | Weathering and UV resistance during long parked periods | Heat management and grip during regular driving |
| Steering and drive forces | Not designed for them | Built to handle them |
When an LT Tire on a Trailer Can Make Sense — and Why It's Debated
This is a genuinely contested topic among trailer owners, so here is the honest version of both sides.
The case for LT tires: Some owners of heavy fifth-wheel and large travel trailers run LT tires and report good service from them. Their arguments: LT tires are built to survive the heat and stress of powered highway axles, many are available in heavy-duty load ranges, and truck tires have a long track record at sustained highway speeds. For a big trailer that logs serious highway miles, some owners consider a quality LT tire a legitimate option.
The case for staying with ST: ST tires are the only category engineered specifically for trailer duty — the sway resistance, the parked-life compounds, and the higher load capacity per size all exist because of how trailers are actually used. Modern ST designs have also improved, and many now carry molded speed rating letters; our trailer tire speed rating guide explains how to read yours. Most trailer and tire manufacturers specify ST tires for their products.
If you do consider the switch, two things are non-negotiable. First, the replacement tire's load capacity must meet or exceed what your trailer's axle rating and placard require — our load range guide covers how to check this. Second, regulations differ by jurisdiction, and your trailer manufacturer's documentation may specify a tire type. Check your state's requirements and your owner's manual before changing tire categories; this guide is general information, not a substitute for either.
FAQ
Can I put LT tires on my trailer?
Sometimes. Some owners of heavy trailers do, but the LT tire must meet or exceed your trailer's required load capacity, and you should confirm your state's regulations and your trailer manufacturer's guidance first. For most trailers, an ST tire remains the straightforward choice.
Why do ST tires carry more weight than LT tires of the same size?
Because ST tires skip the design compromises that driving demands. With no steering, braking, or drive forces to manage, the casing and sidewall can be reinforced purely for load, which is exactly what a trailer axle needs.
How do I know which type is on my trailer right now?
Look at the sidewall. The size will start with ST (for example, ST205/75R15) or LT. If it starts with P, or has no letter prefix, it is a passenger-type tire and should come off the trailer — see our guide on why car tires don't belong on trailers.
When you're ready to replace yours, every ST tire in our trailer tires collection ships free from our Orlando, FL warehouse — and if you'd rather talk through sizing first, call us at (407) 821-7008.