Trailer Tire Sizes, Load Ranges and Bolt Patterns Explained

Buying trailer tires is simple once you know what the numbers on the sidewall mean. This guide covers the three things that have to match your trailer: the tire size, the load capacity, and, if you are buying a complete tire-and-wheel assembly, the bolt pattern.

Trailer tires are different from car tires

Tires marked ST (Special Trailer) are built for trailers. They typically have stiffer sidewalls to carry heavy loads and resist sway, and they are not designed for the steering and braking demands of a car or truck. Use ST tires on trailers, and do not use them on a tow vehicle.

How to read the tire size

Most trailer tires use a metric size such as ST205/75R15:

• ST means Special Trailer.
• 205 is the tire's width in millimeters.
• 75 is the aspect ratio: the sidewall height is 75% of the width.
• R means radial construction. A D (or a dash) means bias-ply.
• 15 is the wheel (rim) diameter in inches.

Small trailers sometimes use a different format, such as 4.80-12 or 20.5x8.0-10. In every case, the safest choice is to replace a tire with the same size shown on your current sidewall or your trailer's VIN or tire placard.

Load range and load capacity

Load range is a letter that tells you how much weight a tire can carry at its maximum rated pressure. Common trailer ratings are:

• Load range B (4-ply rating)
• Load range C (6-ply rating)
• Load range D (8-ply rating)
• Load range E (10-ply rating)

The exact maximum load in pounds is molded on the sidewall. To check that a set of tires is strong enough, add up the loaded weight of the trailer and its cargo, then make sure the combined capacity of the tires on the ground is at or above that number. Many owners choose tires with some capacity to spare. Never exceed the maximum load or pressure molded on the tire.

Radial or bias-ply?

Radial trailer tires generally run cooler, ride more smoothly and wear more evenly on long highway trips. Bias-ply tires have stiffer sidewalls and are often chosen for trailers that carry heavy loads at low speeds or sit parked for long periods. Avoid mixing radial and bias-ply tires on the same axle.

Bolt pattern and other wheel fitment

If you are buying a tire already mounted on a wheel, the wheel must fit your hub. The bolt pattern is written as the number of lug studs and the diameter of the circle through their centers. For example, 5 on 4.5 (5x4.5) means five studs on a 4.5 inch circle. Common trailer patterns include 4 on 4, 5 on 4.5, 5 on 4.75, 6 on 5.5 and 8 on 6.5.

To measure a 4-lug or 6-lug pattern, measure from the center of one stud to the center of the stud directly across. For a 5-lug pattern, measure from the center of one stud to the outer edge of the stud farthest from it, which gives a close approximation. Also check that the wheel's center hole clears your hub and that the wheel's load rating is at least as high as the tire's.

Pressure, speed and age

• Pressure: check the pressure cold, before towing, using the pressure on the tire sidewall or your trailer's placard. Underinflation is a leading cause of trailer tire failure.
• Speed: many trailer tires carry a speed rating or a maximum speed on the sidewall. Do not tow faster than the tire is rated for.
• Age: trailer tires often age out before the tread wears out. The last four digits of the DOT code show the week and year the tire was made (for example, 2324 means the 23rd week of 2024). Inspect older tires for cracks and follow the tire maker's age guidance.

Shop trailer tires

Browse trailer tire & wheel assemblies, the full tires & wheels collection, and golf cart, ATV/UTV & mower tires. Each listing shows the size and fitment details for that tire or assembly. Not sure what fits? Contact us with the size on your current sidewall and your bolt pattern.