Trailer Tire Replacement: How to Choose Suitable Replacement Tires
The Short Answer
A suitable replacement trailer tire matches the original equipment in size, fits the existing wheel, and carries at least the load capacity the trailer manufacturer specifies at the stated inflation pressure. In most cases this means a tire with the same size designation and the same or higher load range. Choose a tire built for trailer service, usually marked ST (Special Trailer), unless the trailer manufacturer specifies something else. Also check that its speed rating covers the speeds you actually tow at, and that it is fresh rather than old stock.
The authoritative values for your trailer are on its certification or tire information label, usually on the tongue or the front left side of the body, and in the owner's documentation. The numbers on the old tires are a useful cross-check. They are not proof of what the trailer requires, because a previous owner may have fitted something different. This guide cannot give values for a specific trailer, because none were supplied. Treat any figure you need for your trailer as something to confirm from its label, its manufacturer or the tire maker's load tables.
Key Terms on a Trailer Tire Sidewall
ST: Special Trailer. A tire designed for trailer axles. It is built to carry heavy loads and resist sidewall flex from sway and tight turns, but it is not meant to steer or drive a vehicle. Size designation: For example, a format such as ST205/75R15. Read it as type, section width in millimetres, aspect ratio, construction (R for radial, D or a dash for bias-ply) and rim diameter in inches. Some trailer tires instead use an older numeric format, such as 4.80-12. Load range: A letter (such as C, D or E) indicating the tire's strength and the inflation pressure it is designed for. Higher letters generally support more load at higher pressure. Load index and maximum load: The maximum weight each tire can carry, printed on the sidewall alongside the maximum cold inflation pressure that capacity depends on. Speed rating: A letter showing the maximum speed the tire is rated for under its rated load. Not every trailer tire is marked with one, and trailer tires have often carried lower speed ratings than passenger car tires, so read the sidewall and the manufacturer's literature rather than assuming. DOT code: In the United States, a code on the sidewall that ends in four digits giving the week and year of manufacture. For example, 2325 would mean the 23rd week of 2025.
How to Choose the Right Replacement
Work through the criteria in this order. Each one is a requirement to meet, not a preference to balance against the others.
1) Size: Use the size listed on the trailer's tire information label. A different size can change ride height, fender clearance and load capacity, and it may not fit the wheel. Only change size with confirmation from the trailer or tire manufacturer. 2) Wheel compatibility: Confirm the rim diameter and width suit the tire, and that the wheel's own load and pressure rating, often stamped on the wheel, is not lower than the new tire's. A higher-load-range tire does not make the trailer stronger if the wheel, axle or suspension is rated lower. 3) Load capacity: Make sure the combined maximum load of all the tires covers the trailer's gross axle weight rating (GAWR), the maximum weight each axle is designed to carry, as shown on the certification label. Many owners and tire makers recommend a margin above the minimum, because trailers are often loaded unevenly or heavier than expected. 4) Speed rating: Pick a tire rated for your typical towing speed. Where a tire's rating is lower than your towing speed, the safe choices are to tow more slowly or to choose a tire with a higher rating. Some tire makers publish guidance on adjusting pressure or load for higher speeds; follow it only where the specific tire maker provides it. 5) Construction: Match construction across each axle, and preferably across the whole trailer. Do not mix radial and bias-ply tires on the same axle. 6) Age: Check the DOT date code before buying or fitting. Trailer tires often age out before they wear out, so avoid tires that have sat in stock for a long time.
Comparing Your Options
Two choices come up most often: which tire type to use, and whether to use radial or bias-ply construction. The table below compares them on general characteristics only. It does not compare specific products, because no measured performance, pricing or test data was supplied.
Option | Intended use | Main advantage | Main limitation; ST tire | Trailer axles | Designed for trailer loads and sway resistance | Not meant for tow vehicles; speed rating varies by tire; LT (light truck) tire | Light trucks; sometimes specified for heavier trailers | Often widely available, sometimes with higher speed ratings | Usually carries less load than an ST tire of the same size; use only where the trailer manufacturer allows it; P (passenger) tire | Passenger cars | Common and comfortable on cars | Generally unsuitable for trailers unless the trailer was specifically designed and labelled for them; Radial construction | Highway and long-distance towing | Typically runs cooler, gives more even tread wear and rolls more easily | Sidewalls can be more flexible, which some owners notice as sway on lightly built trailers; Bias-ply construction | Short trips, low speeds, utility and farm trailers | Stiff sidewalls; often lower purchase price | Tends to run hotter at sustained highway speed and wear faster
For a trailer used mainly at highway speeds over long distances, a radial ST tire in the specified size and load range is the most common fit. For a light utility trailer used for short, slow trips, bias-ply ST tires remain a reasonable, lower-cost choice if they meet the load requirement. If you are considering LT tires, check whether the trailer manufacturer approves them. Then confirm from the tire maker's load table that the LT tire's capacity at your inflation pressure still covers the axle rating. Price and availability differ by market and change over time, so compare current quotes for the same size and load range rather than relying on general claims about cost.
When to Replace Trailer Tires
Replace a tire when its tread is worn to the legal or manufacturer's minimum, or when you see cracking in the sidewall or tread grooves, bulges, cuts, exposed cords, or irregular wear. Also replace tires that have reached the age limit recommended by the tire maker. Age guidance differs between manufacturers, and some jurisdictions have their own rules, so check both. Trailers often sit for long periods, and sunlight, ozone and lack of use can degrade rubber even when the tread looks deep.
Irregular wear is often a symptom of another problem rather than a tire fault. Examples include a bent axle, misalignment, worn suspension parts or wheel bearing trouble. If you find uneven wear, have the axle and suspension inspected before fitting new tires, or the new ones may wear the same way.
How to Replace a Trailer Tire
Many owners replace a complete wheel-and-tire assembly themselves. Mounting a tire onto a wheel, and balancing it, generally requires tire-shop equipment and is best left to a tire shop. The steps below cover swapping a wheel assembly. Torque values, jacking points and tightening sequences differ by trailer and wheel, so take them from the trailer or axle manufacturer's instructions.
What You Need
Replacement wheel and tire assembly, checked against the tire information label; A jack rated for the trailer's weight, or a trailer-specific ramp-style changer where suitable; Jack stands rated for the load; Wheel chocks; A lug wrench that fits the lug nuts; A torque wrench and the manufacturer's lug nut torque specification; A tire pressure gauge
Steps
1) Park on firm, level ground away from traffic. If the trailer is uncoupled, make sure it is stable on its jack or supports. If it is coupled, set the tow vehicle's parking brake. 2) Chock the wheels on the side you are not lifting. Stop if the ground is soft or sloped and you cannot make the trailer stable. 3) Loosen the lug nuts slightly while the tire is still on the ground. Do not remove them yet. 4) Lift the trailer at a jacking point approved by the manufacturer, usually the axle or frame near the spring hanger. Do not lift on the axle where the manufacturer forbids it, or on thin body panels. 5) Place jack stands before removing the wheel. Never put any part of your body under a trailer supported only by a jack. 6) Remove the lug nuts and the wheel. Before fitting the new assembly, inspect the hub, studs, brake components if fitted, and the area around the wheel bearing for damage, grease leaks or looseness. Stop and have the trailer serviced if studs are damaged or the hub has noticeable play. 7) Fit the new wheel. Thread the lug nuts by hand, with the tapered or seat side facing the wheel as the wheel design requires. 8) Lower the trailer until the tire just touches the ground. Torque the lug nuts to the manufacturer's specification in the tightening sequence the manufacturer specifies, typically a star or crisscross pattern. 9) Lower the trailer fully and remove the jack, stands and chocks. 10) Check cold inflation pressure. Set it to the value on the trailer's tire information label or, where the label directs, the value given for that tire by its maker. Do not exceed the maximum pressure on the tire or wheel.
Completion Check
Confirm all lug nuts are torqued and pressures are correct on every tire, including the spare. Check that the wheel spins freely without rubbing or grinding. Many axle and wheel manufacturers call for re-checking lug nut torque after a short initial distance with new or refitted wheels; follow the interval your manufacturer gives. After the first trip, look for uneven tire temperature, vibration or any wobble, and have the trailer inspected if any appear.
When to Use a Professional
Have a qualified shop do the job if you need to mount tires on wheels or balance them, or if a stud, hub or bearing is damaged. The same applies if brakes are fitted and show wear or damage, or if you are unsure of the correct jacking point or torque values. Seek professional advice before changing the tire size, the tire type or the wheels from what the trailer was certified with.
What This Guide Cannot Confirm
No specific trailer model, market, tire product or regulatory text was supplied for this guide. That means it cannot state the correct size, load range, pressure, torque value, speed limit for a particular tire, or a legal tread or age limit for your jurisdiction. Take those details from your trailer's certification and tire information labels, the trailer and axle manufacturers' instructions, the tire maker's published load and inflation tables, and the regulations where you tow.