Trailer Tyre (Tire) Pressure When Towing & Loaded 2026

Trailer tyre (tire) pressure: the quick answer

Set the trailer’s tyres to the cold pressure on its placard or in its manual, which is given for the trailer fully loaded. Set the tow vehicle’s tyres to the full-load or towing pressure in its handbook. Check both when cold, before you hitch up, and never go above the maximum pressure printed on the sidewall.

💡 Calculate yours: Tyre Pressure Calculator gives the correct car tyre PSI/bar for your load. Trailer tyres still follow the trailer’s own placard.

Where the trailer’s pressure figure comes from

Trailers sold in the US carry a federal certification/VIN label on the front half of the left (road) side. It shows the Gross Vehicle Weight Rating (GVWR), which is the most the fully loaded trailer may weigh, and a Gross Axle Weight Rating for each axle. Lighter trailers must also have a tyre and loading information placard in the same place. It lists tyre size, cold tyre pressure and maximum cargo weight. Heavier trailers are not required to have one.

Wheel and tyre makers advise setting trailer tyres to the trailer maker’s cold pressure for the trailer loaded to its GVWR. Use that figure every time you tow, whether the trailer is full or half-empty. If the trailer has no placard (common on older, imported or home-built UK, Canadian and Australian caravans and trailers), use the trailer’s manual or chassis plate. If neither gives a figure, use the tyre maker’s load-and-inflation table for the axle load you have actually weighed.

Fit tyres of the same type, size and construction on every trailer wheel. Don’t mix bias-belted and radial tyres, and buy the size, type and load range shown on the certification label or in the manual. “ST” on the sidewall means the tyre is for trailer use only.

Tow vehicle tyres: the full-load setting

The tow vehicle’s normal pressure assumes its usual load. NHTSA warns that tow vehicle tyres may need a higher pressure for towing, especially with heavy loads. Most handbooks print a second, higher figure for full load, usually on the same door-frame or fuel-flap placard as the normal one. Some vehicles have separate front and rear figures, because the weight on the hitch presses down mostly on the rear axle.

Part of the trailer’s weight transfers to the tow vehicle and uses up some of its cargo capacity. The vehicle manual explains how much. Tongue weight that is too high can also take weight off the front wheels and make the steering less responsive. See the tyre pressure guide for how normal and full-load figures appear on placards.

Why under-inflation is the bigger risk when loaded

Air pressure is what lets a tyre carry its load. NHTSA’s towing guidance says under-inflation lowers the load-carrying capacity of both the tow vehicle and the trailer. It can cause sway and control problems, and it can overheat the tyre until it blows out or fails in another way. Over-inflation wears tyres early and changes how the tow vehicle and trailer handle.

Heavy loads and low pressure have the same effect: the tyre flexes too much and builds up excess heat, which can lead to failure. Running a trailer tyre under-inflated even briefly can damage it internally. Hot weather and fast towing speed this up, so moderate speeds help. NHTSA also notes that sway gets more likely as speed rises.

Load rating, load range and the sidewall maximum

A tyre’s load rating is the most it may carry at a given pressure. Its maximum load rating applies only at the maximum permissible inflation pressure printed on the sidewall. The pressure on the trailer’s placard should never exceed that sidewall maximum. Load range tells you how much the tyre can carry and its inflation limits. See understanding tyre load index for how the load index number translates into kilograms and pounds.

For tow vehicles, the federal calculation assigns a standard weight to each occupant. If your crew and luggage are heavier, you may need the full-load pressure even before you hitch up.

Cold readings, warm tyres and monitoring systems

“Cold” has nothing to do with the weather. It means the tyre has not been driven for at least three hours. Pressure rises as tyres warm up, so a reading taken at a services stop will be higher than the cold figure. If a warm tyre is clearly low, fill it to the recommended cold pressure as a temporary fix and recheck it once it has cooled.

A trailer tire monitoring system shows pressure while you drive, which helps you catch a slow leak early. Its readings are warm values, though. Set pressures with a gauge when the tyres are cold, and treat the monitor as a warning device, not the setting.

What to do before a towing trip

1. Find both figures. Get the trailer’s placard or manual pressure and the tow vehicle’s full-load or towing pressure. Note which units each uses.
2. Check cold, all round. Before you hitch up, check and correct the pressure on every tyre of the tow vehicle and trailer, spares included.
3. Compare with the sidewall maximum. If the pressure you plan to use is above the tyre’s maximum permissible pressure, the tyre is wrong for the load. Replace it with the load range on the trailer label. Don’t over-inflate it.
4. Weigh, don’t guess. Weigh the loaded rig at a public weighbridge or scale. Spread the cargo evenly front to back and side to side, keep heavy items low and near the axle, and stay within the GVWR and axle ratings.
5. Inspect. Look for cuts, cracks, uneven wear and anything stuck in the tread. Uneven wear can point to an alignment problem. See tyre rotation and alignment.
6. Recheck at stops. If a tyre reads low when warm, top it up to the cold figure and check again once it has cooled.
7. Reset after unhitching. Once you’re no longer towing, put the tow vehicle back to its normal-load pressure.

Sources

• NHTSA, Towing a Trailer: Being Equipped for Safety.
• Tire safety information required by US federal regulation, including text from NHTSA’s Tire Safety: Everything Rides On It, as printed in a trailer owner’s manual.