Enclosed Trailer Tire Guide: Sizes, Load Ratings, Pressure & Maintenance
Trailer tires are one of the most important components affecting towing safety, load capacity and reliability. Whether you own a small single-axle cargo trailer or a large enclosed car hauler, choosing the correct tires—and maintaining them properly—can help prevent premature wear, tire failure and roadside problems.
This guide explains trailer tire types, load ranges, tire pressure, sizing, replacement and the warning signs trailer owners should watch for.
Southern Trailer Depot has been helping customers choose enclosed trailers since 2007. Our team can help you match the right trailer, axle package and tire setup to your hauling needs.
Tires are just one part of a trailer’s overall construction. For a complete look at frame, axles, suspension and other build factors, see our Enclosed Trailer Construction Guide.
Why Trailer Tires Matter
Trailer tires support the entire loaded weight of the trailer while dealing with heat, highway speeds, road impacts and forces created during turning and maneuvering.
The correct tire should be selected based on the trailer manufacturer's specifications and the tire's:
- Size
- Load range
- Maximum load capacity
- Maximum inflation pressure
- Speed rating
- Wheel size
- Intended application
Never select a replacement tire based on appearance or physical size alone.
ST vs. LT Tires: What's the Difference?
Many trailers use tires marked ST, meaning Special Trailer.
ST tires are specifically designed for trailer applications. They are not intended for use as steering or drive tires on passenger vehicles.
LT means Light Truck. Some trailers may be manufactured or certified with LT tires depending on the application.
Important
Do not automatically substitute an LT tire for an ST tire—or an ST tire for another tire type—without confirming that the replacement meets the trailer manufacturer's requirements for size, load capacity and application.
How to Read a Trailer Tire Size
A common trailer tire size may look like:
ST225/75R15
Here's what that means:
ST — Special Trailer tire
225 — Approximate section width in millimeters
75 — Aspect ratio
R — Radial construction
15 — Wheel diameter in inches
Understanding Trailer Tire Load Range
Common trailer tire load ranges include:
| Load Range | Common Trailer Application |
|---|---|
| C | Smaller and lighter trailers |
| D | Medium-duty trailer applications |
| E | Many heavier tandem-axle trailers |
| F | Heavy-duty trailer applications |
| G | Higher-capacity commercial/heavy trailer applications |
Do not choose tires based on load-range letter alone. Always verify the specific tire's maximum load rating and required inflation pressure printed on its sidewall.
Different tires within the same general category can have different specifications.
Tire Capacity and Trailer GVWR
Your tires must have enough capacity for the trailer and its intended load.
For example, if a tire is rated for a maximum load of 2,830 lbs, four tires would have a combined mathematical tire capacity of:
2,830 lbs × 4 tires = 11,320 lbs
However:
Tire capacity does NOT automatically determine trailer GVWR.
The trailer's certified GVWR may be limited by other components, including:
- Axles
- Wheels
- Frame
- Suspension
- Coupler
- Brakes
- Tires
- Manufacturer certification
The trailer's certification/VIN label should be used to determine its certified GVWR and GAWR.
For more on axle capacity ratings and how they should be matched to tires and GVWR, see our Trailer Axle Guide.
Trailer Tire Pressure
Correct tire pressure is critical for trailer tire performance.
Always check tire pressure according to the tire and trailer manufacturer's specifications.
Tire pressure should generally be checked before towing while the tires are cold, because pressure increases as tires heat up during operation.
BEFORE EVERY TRIP
Check trailer tire pressure before towing while the tires are cold.
Don't Forget the Spare Tire
A properly equipped spare tire can prevent a tire problem from turning into a much larger roadside issue.
Before a long trip, inspect the spare just like the tires currently on the trailer.
Check:
- Tire pressure
- Tire condition
- Correct tire size
- Load rating
- Wheel compatibility
- Mounting hardware
A spare tire that has been sitting unused for years can still deteriorate.
Watch for Uneven Trailer Tire Wear
Your tires can provide clues about problems elsewhere on the trailer.
CENTER TREAD WEAR
May be associated with excessive inflation or other tire/application issues.
BOTH OUTER EDGES WORN
May be associated with insufficient inflation, overloading or other conditions.
ONE-SIDED WEAR
Could indicate an alignment, axle, suspension or loading issue.
CUPPING OR IRREGULAR WEAR
May indicate wheel balance, bearing, suspension, alignment or other mechanical issues.
RAPID OR UNUSUAL WEAR
Should be investigated rather than simply replacing the tire and continuing to tow.
If tire wear appears abnormal, have the trailer and tire condition properly inspected.
Trailer Tire Age Matters Too
Tread depth isn't the only consideration when deciding whether a trailer tire needs replacement.
Trailer tires may spend long periods parked outdoors and can deteriorate because of:
- Age
- UV exposure
- Heat
- Weather
- Improper inflation
- Overloading
- Long periods of storage
A tire can have substantial tread remaining and still require replacement because of age or deterioration.
Always follow the tire manufacturer's inspection and replacement recommendations.
How to Find the Age of a Trailer Tire
Look for the DOT Tire Identification Number on the tire sidewall.
The final four digits of the date code identify the week and year the tire was manufactured.
EXAMPLE:
2425
24 = 24th week
25 = 2025
So a tire marked 2425 was manufactured during the 24th week of 2025.
Radial vs. Bias-Ply Trailer Tires
Trailer tires may use radial or bias-ply construction.
| Radial Tires | Bias-Ply Tires |
|---|---|
| Common for highway towing | Common in certain trailer applications |
| Generally run cooler | Different casing construction |
| Often provide good tread life | May be appropriate for specific uses |
| Common on modern enclosed trailers | Selection depends on trailer requirements |
For most customers, the best choice is to stay with the tire construction and specifications recommended by the trailer and tire manufacturers unless an appropriate change has been verified.
Inspect Your Trailer Wheels Too
Tire maintenance should include wheel inspection.
Check the wheels for:
- Cracks
- Bending or deformation
- Damage around lug holes
- Corrosion
- Loose or missing lug nuts
- Valve-stem damage
- Other visible damage
Wheel load capacity and specifications must also be appropriate for the trailer.
Trailer Lug-Nut Torque
Loose wheel nuts can cause serious wheel and hub damage.
Wheel-nut torque should be checked according to the wheel, hub, axle and trailer manufacturer's procedures and specifications.
Newly installed wheels may require torque checks after short initial travel intervals.
When Should Trailer Tires Be Replaced?
Trailer tires should be replaced when their condition no longer meets the tire manufacturer's requirements or when damage makes continued use unsafe.
Reasons a tire may require replacement include:
- Excessive tread wear
- Cracking or weather checking
- Bulges
- Cuts or puncture damage
- Exposed cords
- Significant uneven wear
- Impact damage
- Age-related deterioration
- Damage from running underinflated
- Damage from overloading
Do not rely on tread depth alone when evaluating an older trailer tire.
Trailer Tire Storage Tips
If your enclosed trailer will sit for an extended period:
- Maintain the recommended tire pressure.
- Keep the trailer parked on a clean, firm surface when possible.
- Minimize prolonged exposure to standing water.
- Protect tires from unnecessary UV exposure when practical.
- Inspect tires before returning the trailer to regular use.
- Do not assume an unused tire is automatically in good condition.
Common Trailer Tire Mistakes to Avoid
Avoid these common problems:
❌ Running underinflated tires
Can increase heat buildup and tire damage.
❌ Overloading the trailer
Can overload tires, axles and other components.
❌ Ignoring tire age
Low mileage doesn't necessarily mean a tire is in good condition.
❌ Ignoring unusual tread wear
Abnormal wear can be evidence of another trailer problem.
❌ Forgetting the spare
The spare needs inspection and proper inflation too.
❌ Installing the wrong tire
Replacement tires should meet the required size, type, load capacity and other specifications for the trailer.
Choosing the Right Trailer for Your Load
Tires are only one part of the trailer's overall capacity.
Before purchasing an enclosed trailer, consider:
- What you're hauling
- Loaded cargo weight
- Trailer empty weight
- Required payload
- GVWR
- Axle capacity
- Tire and wheel capacity
- Tow-vehicle capacity
- Braking requirements
- Typical towing distance
A customer hauling lawn equipment in a 6×12 has very different requirements from someone hauling a race car and equipment in an 8.5×24 enclosed trailer.
Shop Enclosed Trailers at Southern Trailer Depot
Southern Trailer Depot carries enclosed trailers for everything from personal hauling and lawn equipment to motorcycles, side-by-sides, cars, race equipment and commercial applications.
Available configurations may include:
- Single and tandem axles
- Multiple GVWR packages
- Torsion axles
- Spread axles
- Blackout packages
- Polycore exteriors
- Semi-screwless exteriors
- Finished interiors
- Cabinets
- E-track
- Air conditioning
- Generator compartments
- Awning packages
- Custom configurations
We've Got Your Trailer
Southern Trailer Depot
Douglas, Georgia
Call: 1-888-403-1902
Tire condition is one of several factors that can contribute to trailer sway. For a full look at proper cargo placement, see our trailer loading guide.