What Size Are Trailer Tires? Sizes Chart & Guide

Towing safely begins where your trailer meets the road. Towing enthusiasts, commercial haulers, and weekend campers often ask: what size are trailer tires? The short answer is that trailer tires span from compact 8" pneumatic tires for small pull-behinds to robust 16" commercial-grade radials designed for heavy haulers.

Selecting the correct tire prevents blowouts, protects your cargo, and maintains stable tracking at speed. This guide delivers technical specifications, dimensions, bolt patterns, and load recommendations to help you select the exact match for your equipment.

Trailer tire size chart

Refer to this comprehensive trailer tire size chart to quickly identify tire diameters, section widths, and typical uses. All dimensions follow current industry tire standards for ST (Special Trailer) applications.

Reviewing the table reveals common trailer tire sizes like ST205/75R15 and ST225/75R15 across standard road rigs. Always confirm your fender clearance before increasing diameter or width.

Trailer wheel sizes & compatibility

Matching tires to wheels requires checking rim diameter, rim width, bolt pattern, pilot hole diameter, and offset. A tire cannot function safely if mounted on a wheel with incompatible dimensions.

Rim diameter measures the distance across the wheel bead seat where the tire bead rests. Width measures the distance between the inside of the rim flanges, not the outside lip. An ST205/75R15 tire fits a 15" rim, typically between 5.0" and 6.5" wide, with 5.5" or 6.0" serving as the ideal width.

Bolt pattern consists of the number of lug studs and the diameter of the circle they form. The most widespread trailer wheel sizes feature these standard hub configurations:

1. 4 on 4.0": Common on 8", 10", and 12" wheels for light-duty haulers.
2. 5 on 4.5": The most frequent hub size for 13", 14", and 15" wheels on 3500 lbs axles.
3. 5 on 4.75" or 5 on 5.0": Occasional configurations for specific camper and boat brands.
4. 6 on 5.5": Standard pattern on 15" and 16" wheels supporting 5200 lbs to 6000 lbs axles.
5. 8 on 6.5": Commercial spec for 16" and 17.5" wheels mounted on 7000 lbs to 10000 lbs axles.

To measure a 4-lug, 6-lug, or 8-lug pattern, measure center-to-center across 2 opposing studs through the hub center. For a 5-lug pattern, measure from the center of 1 stud straight across to the outer edge of the opposing stud.

Trailer wheels generally feature 0 offset, meaning the mounting pad sits flush with the centerline of the rim. This orientation distributes weight evenly across axle bearings. Car wheels often feature a positive offset, which pushes the wheel inward. Using passenger car rims on trailer hubs can cause tires to rub against the suspension springs or inner frame rails.

Hub center bore is equally critical. Most trailer hubs operate as lug-centric systems, where conical 60-degree lug nuts center the wheel onto the hub. The center hole must remain large enough to clear the axle grease cap without binding.

Trailer tire sizes by trailer type

Different trailers handle distinct load requirements, terrain, and distances. Axle ratings, deck heights, and tongue geometries influence the tire dimensions chosen by manufacturers.

Utility trailer tires

A general-purpose open-bed utility trailer often handles mulch, lawn mowers, building materials, and off-road vehicles. Single-axle versions rated for 2000 lbs to 3500 lbs Gross Vehicle Weight Rating (GVWR) lean heavily on 12", 13", and 15" fitments.

For 2000 lbs axles, 4.80-12 or 5.30-12 bias tires provide a low deck height for easy loading. For 3500 lbs axles, manufacturers install ST205/75R15 tires. This dimension delivers ample sidewall cushion, simple access to replacements, and high load capacity per unit.

Boat trailer tires

Boat haulers deal with regular water submersion, sustained high speeds, and long stationary periods. Marine trailers favor low-profile, stable tires that keep the boat hull low for shallow ramp launchings.

Small fishing skiffs and personal watercraft use 4.80-12 or 5.30-12 trailer tire sizes. Medium fiberglass and aluminum hulls between 18' and 24' ride on ST175/80R13 or ST205/75R14 tires. Large offshore vessels require tandem or triple axles equipped with ST225/75R15 radial tires to absorb shock and protect marine hulls from stress fractures.

Travel trailer and camper tires

Campers and recreational rigs travel long distances under continuous maximum loads. Unlike cargo boxes that run empty on return trips, an RV carries its full furniture, appliances, and tank weight continuously.

Pop-up campers use 5.30-12 or ST175/80D13 tires. Mid-size bumper-pull travel trailers rely on ST205/75R14 or ST205/75R15 radials. Heavy fifth-wheels and luxury multi-slide rigs shift to ST235/80R16 or ST235/85R16 tires in Load Range E or G. Radial construction provides reduced rolling resistance, lower heat production, and superior handling over continuous highway travel.

Enclosed cargo trailer tires

Enclosed cargo haulers transport tools, commercial goods, motorcycles, and race cars. Fleet owners demand high durability, predictable tread life, and simple roadside availability.

Single-axle 5' x 8' and 6' x 12' enclosed trailers with a 2990 lbs to 3500 lbs GVWR rely on ST205/75R15 tires. Tandem-axle 7000 lbs GVWR box trailers utilize 2 matching 3500 lbs axles running 4 ST205/75R15 tires. Tandem 10000 lbs cargo haulers step up to ST225/75R15 Load Range E tires, providing up to 2830 lbs of capacity per tire at 80 psi.

Heavy equipment and gooseneck trailer tires

Commercial operators pulling mini-excavators, skid steers, and tractors require heavy-duty tires with rigid sidewalls and high plies.

Tandem 7000 lbs or 8000 lbs axles on gooseneck and deckover flatbeds run ST235/80R16 or ST235/85R16 radials with 10-ply (Load Range E) or 14-ply (Load Range G) configurations. Super-duty trailers with 10000 lbs to 12000 lbs axles often step up to commercial 17.5" wheels mounted with 215/75R17.5 or 235/75R17.5 16-ply tires rated beyond 4800 lbs per tire.

How to choose the correct trailer tire size

Picking replacement tires requires more than matching the coding on the old rubber. Parts wear, previous owners make errors, and payload requirements shift. Use this systematic approach to choose your gear safely.

When decoding the tire sidewall, review these trailer tire sizes explained:

• Prefix: "ST" stands for Special Trailer. These tires feature thicker sidewalls, heavier polyester cords, and stiffer steel belts than passenger (P) or light truck (LT) tires to combat lateral sway.
• Section Width: The 1st 3 digits (e.g., 205 in ST205/75R15) specify width in mm from sidewall to sidewall.
• Aspect Ratio: The 2 digits after the slash (e.g., 75) show sidewall height as a percentage of section width. A 75 aspect ratio means sidewall height equals 75% of 205 mm (153.75 mm).
• Internal Construction: An "R" indicates radial construction, where internal cords run 90 degrees to the direction of travel. A "D" indicates diagonal bias-ply construction, where plies crisscross at 30-degree angles.
• Rim Diameter: The final 2 digits indicate wheel diameter in inches (e.g., 15").

For legacy fitments, you will spot standard numerical sizing like 4.80-12 or 5.30-12. Here, the 1st number gives section width in inches (4.80"), while the 2nd number shows the rim size (12").

Tire sidewalls display stamped identification codes, date codes, and load numbers indicating max weight limits and cold inflation pressures.

To match capacity, calculate your Gross Axle Weight Rating (GAWR). A tandem-axle hauler with 2 3500 lbs axles requires a minimum aggregate tire capacity of 7000 lbs. Divide by 4 tires to get an absolute minimum load rating of 1750 lbs per tire.

Choose a load range with a safety margin above that baseline:

• Load Range B: 4-ply rated, up to 35 psi
• Load Range C: 6-ply rated, up to 50 psi
• Load Range D: 8-ply rated, up to 65 psi
• Load Range E: 10-ply rated, up to 80 psi
• Load Range F: 12-ply rated, up to 95 psi
• Load Range G: 14-ply rated, up to 110 psi

Physical clearance represents the next check. Ensure at least 3" of vertical clearance between the top of the unloaded tire tread and the underside of the fender to accommodate suspension bounce. Allow 1" to 1.5" of horizontal clearance between the inner tire sidewall and the trailer chassis or leaf springs.

Decide between radial and bias designs:

• Radial Tires: Best for road travel, long road trips, and commercial hauling. They run cooler, offer superior tread life, and deliver smoother tracking. A luxury motorhome tow dolly or cross-country camper thrives on radials.
• Bias Ply Tires: Best for slow speeds, farm tasks, off-road applications, short local runs, and construction sites. Their crosshatch sidewalls offer higher puncture resistance against tree roots and sharp curbs.

Finally, verify speed ratings. Older bias designs carried 65 mph limitations. Modern ST radials carry speed ratings such as M (81 mph), L (75 mph), or J (62 mph). Ensure your tire speed rating matches actual interstate travel conditions.

Across the United States, the ST205/75R15 serves as the most widespread standard trailer tire size for standard light-to-medium utility and enclosed haulers. Confirming this size on your trailer certification label guarantees proper fit and load stability.

Frequently Asked Questions

Can passenger car tires replace ST trailer tires?

No, you should never mount passenger car tires on trailers. Passenger tires feature flexible sidewalls designed for passenger comfort, which causes severe sway, fishtailing, and rollover risk on trailers. ST tires feature stiffened sidewalls and heavy-duty steel cord belts designed specifically to support heavy vertical loads and combat severe lateral sway.

What air pressure should I run in trailer tires?

Always inflate trailer tires to the maximum cold psi stamped on the sidewall. Running lower pressure generates excessive heat, weakens internal steel belts, reduces load capacity, and causes sudden blowouts. Check pressures when tires are completely cold before towing.

How do I calculate total trailer tire capacity?

Multiply the maximum load rating of a single tire by the total number of tires on your trailer. For instance, 4 tires rated at 1760 lbs each provide 7040 lbs of total tire capacity. Ensure this combined number equals or exceeds your trailer gross axle ratings.

How often should trailer tires be replaced?

Replace trailer tires every 3 to 5 years, regardless of remaining tread depth. Trailer tires sit stationary under load for long stretches, exposing rubber compounds to UV degradation and internal ozone rot. Check for sidewall cracking, bulging, or irregular tread wear before every towing trip.

What are the standard dimensions of trailer tyres?

The most common dimensions across standard trailers are ST205/75R15 and ST225/75R15. An ST205/75R15 measures 27.1" in diameter with an 8.1" width on a 15" rim. An ST225/75R15 measures 28.3" in diameter with an 8.8" width. Smaller trailers rely on 4.80-12 sizes measuring 20.7" in diameter and 4.8" wide.