How to Check Trailer Tire Pressure and Load Range
Updated: 1 day ago
Trailer tires live a harder life than the tires on your tow vehicle. They carry a heavy, mostly static load, they get scrubbed sideways on every tight turn of a tandem axle, and they sit for weeks or months between trips. Most trailer blowouts trace back to the same root cause: a tire that was underinflated, overloaded, or simply too old. Checking pressure correctly and knowing what your load range means takes a few minutes and protects the aluminum skin and wheel wells of your Airstream from the damage a tread separation can do.
Find the Right Pressure for Your Trailer
Start with the tire and loading information placard on the trailer itself. It lists the original tire size and the recommended cold inflation pressure for the trailer as built. Its location varies by year and model, so check your owner's manual if you cannot find it on the exterior near the front or inside a door or cabinet. If you have changed tire brand, size, or type since the trailer left the factory, use the load and inflation table published by the tire manufacturer for your exact tire, matched to your actual axle weights.
The number molded on the sidewall is the maximum pressure the tire is rated for and the pressure at which it reaches its maximum load capacity. Many trailer owners run ST tires at that sidewall maximum for the extra load margin, and some tire makers recommend exactly that for ST tires. Whatever you choose, never exceed the sidewall maximum or the wheel's maximum pressure rating, and never go below the pressure needed to carry your actual load.
What Load Range Means
Load range is a letter that describes how strong the tire's construction is and how much pressure it can hold. For common ST trailer tires, load range C is typically rated to 50 psi, D to 65 psi, and E to 80 psi, though you should always confirm with the sidewall of your specific tire. A higher load range only carries more weight when it is inflated to the higher pressure. A load range E tire run at 50 psi carries roughly what a load range C tire carries at 50 psi.
Airstreams have shipped on both ST (special trailer) and LT (light truck) tires depending on model and year. The two are not interchangeable on paper; they use different load tables. Know which one you have and use the matching table. If you are replacing tires, match or exceed the original load capacity and make sure the wheels are rated for the pressure you plan to run.
Check Your Real Weight Once
Pressure only means something relative to load. Take the trailer, loaded the way you travel, across a certified truck scale. Weigh the trailer axles separately from the tow vehicle. Divide each axle weight by the number of tires on it and compare that to the load capacity printed on the sidewall at the pressure you run. Leave yourself a margin; many owners aim to use no more than 80 to 90 percent of the tire's rated capacity. If you are near the limit, you need more pressure (up to the max), a higher load range, or less stuff.
How to Check Pressure the Right Way
Check cold. Cold means the trailer has not been driven yet that day, or has sat for at least three hours out of direct sun. Driving warms the air inside the tire and raises pressure, so a hot reading will mislead you.
Use a good gauge. Stick gauges at the gas station are often off by several psi. A quality digital or dial gauge rated past your target pressure is worth keeping in the truck. Check it occasionally against a second gauge.
Press straight and firm. Remove the valve cap, press the gauge squarely onto the stem until the hiss stops, and read. If you get an odd number, take it again.
Adjust to target. Add air in short bursts and recheck. If a tire is high because the morning is warm, do not let air out of a tire that is still hot from driving. Set pressure only when cold.
Check the spare too. A spare at 20 psi is not a spare. Include it every time.
Cap every valve. Valve caps keep dirt out of the core and act as a backup seal. Metal-sleeved or sealed caps are a small upgrade worth making.
Write it down. Note the date, temperature, and each tire's reading. A tire that loses a few psi every week has a slow leak at the bead, valve, or tread that you want to find at home, not on the interstate.
Inspect While You Are Down There
Age: find the DOT code on the sidewall. The last four digits are the week and year of manufacture, so 2321 means the 23rd week of 2021. Many trailer owners and tire makers suggest replacing trailer tires around five to six years of age regardless of tread, because rubber degrades with time and sun.
Sidewalls: look for cracks, weather checking, bulges, or cuts. A bulge means internal damage. Replace that tire before you tow.
Tread wear: wear on both shoulders points to underinflation or overload. Wear in the center suggests overinflation for the load. Wear on one edge or a choppy pattern can mean an axle alignment or bearing problem worth having checked.
Lug nuts: confirm they are snug and torqued to spec. See our spare tire carrier and lug torque checklist for the routine.
On the Road
A tire pressure monitoring system is one of the most useful upgrades for a trailer. It warns you about a slow leak or a rising temperature before you can feel anything from the driver's seat. Even with TPMS, put a hand on each tire and hub at fuel stops. They will be warm, but one that is much hotter than its neighbors deserves a closer look. Respect the speed rating of your tires; many ST tires are rated well below typical interstate speeds, so check the sidewall and drive accordingly.
Storage Between Trips
Tires lose a little air every month just sitting. Keep them at full travel pressure in storage, cover them if they sit in direct sun, and park on a solid surface or boards rather than bare dirt. Move the trailer a few feet every couple of months if you can, so the same spot of the tire is not always bearing the load. Then check pressure before the first trip of the season, every time.
Recommended gear
An accurate gauge helps you catch underinflation before heat builds: AstroAI heavy-duty digital tire pressure gauge (paid link) — https://www.amazon.com/dp/B01NCX3H1G?tag=rivetresource-20
As an Amazon Associate, Rivet Resource earns from qualifying purchases. Links marked (paid link) may earn a commission at no extra cost to you. Rivet Resource is an independent owner resource and is not affiliated with or endorsed by Airstream, Inc. Always follow your trailer placard and tire manufacturer's load and inflation data.
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