Trailer Tire Buying Guide: Size, Load Range, Radial vs Bias, and Pressure

The best trailer tires are the ones that match your axle load, speed profile, and service life needs. Not the cheapest ST size on the shelf. Trailer tires run hotter and carry different side loads than passenger car tires. Choose wrong on size, load range, or construction and you invite cupping, blowouts, and short tread life. Shop proven options at The Trailer Parts Outlet.

This buying guide shows you how to read a trailer tire size, choose between ST and LT, compare radial vs bias ply, use a load range chart, and set pressure the right way. When you are ready to order, start in the trailer tires collection or buy matched trailer tires and wheels so every corner matches.

How to read a trailer tire size

Most trailer tires use an ST size string. A common example is ST205/75R15.

 

You will also see older style size formats on some bias tires. When in doubt, match the size printed on the current tire sidewall and confirm load capacity against your trailer GVWR divided across the tire positions. A popular light duty radial example is the ST205/75R15 load range C radial tire. Prefer a ready corner? Shop the matching ST205/75R15 tire and wheel assembly.

ST tire vs LT tire

ST tires are built for trailer use. The construction targets higher load capacity and the side loads that come from being towed rather than steered like a front vehicle tire.

LT tires are light truck tires. Some owners run LT tires on trailers, especially in certain commercial or mixed fleets, but that choice needs careful load and pressure work. An LT tire is not automatically safer on a trailer just because it looks tougher.

Why ST is the default for most trailers

• Load ratings are published for trailer duty patterns
• Sidewall design targets trailer behavior
• Replacement sizes are easy to match across utility, cargo, and many RV trailers in the trailer tires catalog

When LT comes up in conversation

• Some heavy or specialty setups use LT with professional guidance
• Never swap to passenger P metric car tires for trailer service
• If you consider LT, confirm load capacity at the pressure you will actually run and keep the whole trailer matched

Bottom line for most owners  buy ST trailer tires sized and load rated for the trailer, not leftover truck tires from another job.

Trailer tire load range chart

Load range tells you how much weight a tire can support at its rated maximum cold pressure. Higher letters generally mean higher capacity and higher rated pressures. Always read the sidewall for the exact max load and max pressure on the tire you buy, because brands can differ inside a letter class.

 

How to use the chart  add the max load of all tires on the ground, then confirm that number exceeds trailer GVWR with a safety margin. Do not size tires to empty trailer weight. Size them to the loaded trailer you actually tow. Stepping up from load range C, many owners look at ST225/75R15 load range E radial tire or ST235/80R16 load range E radial tire when capacity and wheel diameter call for it.

Radial vs bias ply trailer tires

Radial vs bias ply is a construction choice. It changes ride, heat behavior, wear pattern, and how the tire responds to highway miles.

Radial trailer tires

• Usually run cooler on highway miles
• Often deliver a smoother towing feel
• Typically better tread life in long distance service
• Preferred for most owners who tow at speed on pavement

Bias ply trailer tires

• Often lower purchase price
• Stiffer sidewalls that some owners like for certain trailer types
• Can make sense for lower speed, rougher, or budget focused use
• May wear and heat differently than radials on long highway runs

Which should you buy

If your trailer sees regular highway miles, radial ST tires are the usual best trailer tire choice. If you need a tough budget tire for lower speed local work, bias can still serve. Do not mix radial and bias on the same trailer. Keep construction matched on every position. Shopping convenience winners are complete 15 inch tire and wheel assemblies and 16 inch tire and wheel assemblies.

 

Trailer tire pressure guide

Trailer tire pressure is not a copy of your truck tire habit. Many trailer tires are designed to run at or near the maximum cold pressure printed on the sidewall when carrying rated loads. Underinflation is a leading path to heat buildup and failure.

Practical pressure rules

• Read the max cold PSI on the tire sidewall and the trailer manufacturer guidance on the certification label
• Set pressure cold, before the trailer moves
• Check pressure before long trips and after big temperature swings
• Do not trust a visual look. Trailer tires can look firm while sitting low.
• If you run below rated load, follow the tire maker load and inflation tables when available. Do not invent a low pressure for a softer ride.

Pressure by load range in the real world

Higher load ranges carry higher rated pressures. A load range C tire often lives around a 50 PSI class maximum, while load range D and E step higher. Your exact tire may differ. The sidewall always wins over a blog chart.

If one tire repeatedly loses pressure, find the leak before the next trip. Slow leaks turn into heat events at highway speed.

Trailer tire size and fit checklist

• Match the size your trailer was built around unless you are intentionally reengineering clearance and capacity
• Confirm wheel width and bolt pattern before you buy tire and wheel assemblies
• Check fender and frame clearance through full suspension travel
• Keep all positions the same size, load range, and construction
• Replace in full sets when wear or age is uneven across the trailer

Changing axle capacity or wheel size at the same time? Confirm the new trailer axles and related trailer components before you commit to tires.

When to replace trailer tires

Trailer tires age out even when tread remains. UV, ozone, and time dry the rubber while the trailer sits.

• Replace for age based on the tire maker guidance and common 5 to 7 year service windows many owners use as a hard stop
• Replace sooner for cracks, bulges, exposed cord, impact damage, or repeated punctures
• Replace for uneven wear that points to alignment, balance, or suspension issues after you fix the root cause
• Replace if you cannot hold correct pressure

How to get more life from trailer tires

• Keep pressure correct
• Do not overload past tire or axle ratings
• Cover tires or park out of direct sun when the trailer sits
• Avoid long storage on soft ground that creates flat spots without movement
• Inspect before every long haul, not only at the start of the season
• Balance assemblies and keep lug torque correct after wheel service
• Service hubs on the same maintenance calendar with high temperature wheel bearing grease

Shop trailer tires at The Trailer Parts Outlet

The Trailer Parts Outlet stocks trailer tires and complete assemblies so you can replace a matched set without guessing across vendors.

• Trailer tires collection for ST sizes and load ranges
• 15 inch tire and wheel assemblies
• 16 inch tire and wheel assemblies
• Popular product paths  ST205/75R15 load range C radial tire, ST225/75R15 tire and wheel assembly, ST235/80R16 load range E radial tire

Send us your current size, load range, and trailer type, or call (833) 910 3416. We will help you match a set that supports your loaded weight rather than only your empty trailer weight.

Tires stop the trailer only as well as the brake system behind them. Pair this guide with the electric vs hydraulic trailer brakes guide and the drum brakes vs disc brakes guide. For more owner guides, visit the trailer parts news blog.

Trailer tire FAQs

What are the best trailer tires for highway towing?

Start with radial ST tires in the correct size and load range for your GVWR. Brand choice matters less than correct capacity, fresh date codes, and proper pressure. A common highway starting point is a quality radial such as the ST205/75R15 load range C radial tire when that size matches your trailer.

Can I use regular car tires on a trailer?

No. Passenger car tires are not built for typical trailer loads and duty cycles. Use ST trailer tires unless a specialist setup has been deliberately engineered otherwise.

Should trailer tire pressure match my truck tires?

No. Set trailer tires by the trailer tire sidewall and load needs. Truck and trailer pressures are separate systems.

How do I choose between load range C and D?

Add up required capacity for the loaded trailer. If load range C meets the need with margin and matches the original design, it can be enough. If you work near the limit or haul dense cargo, step up to the higher load range and the wheel rating that supports it.

Bottom line

Choosing trailer tires is a capacity decision first and a brand decision second. Decode the size, confirm ST vs LT, pick radial or bias based on how you tow, and use the load range chart to keep every tire above your real loaded weight. Set pressure cold, inspect often, and replace for age as well as tread. Then order a matched set from The Trailer Parts Outlet through trailer tires or ready trailer tires and wheels assemblies.

The Trailer Parts Outlet, founded in 2013, is a solution-driven parts distributor renowned for its industry-savvy team members and the custom-tailored solutions we provide for every customer. We embody CASS (Convenience, Access, Speed, Simplicity), offering a wide array of trailer repair parts for the hard-working trailer community. Our unparalleled speed and simplicity set us apart, ensuring swift delivery of solutions to get you back on the road. As a company, we genuinely care for our customers, creating lasting relationships and a community of doers. Choose us for quality, reliability, and excellent service steeped in our unique CASS approach.