Adjusting Tire Pressure for Towing: Step-by-Step

Why towing changes tire pressure needs

Adding a trailer changes the load on your vehicle's tires. Tongue weight and cargo shift weight onto the rear axle, increasing the load that each tire must support. A tire's load rating is tied to its inflation pressure: as pressure increases, the rated load capacity increases. When you tow, you need a higher pressure to keep the load rating within safe limits.

Federal regulations define load rating as the maximum load a tire is rated to carry for a given inflation pressure. Your vehicle's placard gives the recommended cold inflation pressure for normal, unloaded operation. That value may not be sufficient when the axle is loaded beyond its normal design load. You need the load and inflation table to find the correct pressure for your towing load.

1. Find the vehicle placard and baseline pressure

The first step is to locate the vehicle placard, usually on the driver's side door jamb, and the tire inflation pressure label. These show the manufacturer's recommended cold inflation pressure for the original tires under normal load. This is your baseline. Federal Motor Vehicle Safety Standard No. 138 defines these labels as the source for the vehicle manufacturer's recommended cold inflation pressure. Learn more about tire pressure basics.

2. Determine the actual load on each tire

Weigh the vehicle on a certified scale with the trailer attached and fully loaded. Weigh the front and rear axles separately. Divide each axle weight by two to get the load on each tire. If your trailer has a weight-distributing hitch, the load distribution changes, so weigh with the hitch adjusted as you will use it. This is the load your tires must support while towing.

3. Use the load and inflation table

Every tire has a load and inflation table published by the tire manufacturer. This table lists the load rating at various cold inflation pressures, from the recommended minimum up to the maximum permissible cold inflation pressure. Find the row for your tire size and locate the inflation pressure that provides a load rating at least equal to the load you calculated. If the table shows a rating below your load, you need a larger tire or a different load range.

For vehicles with a gross vehicle weight rating over 10,000 pounds, Federal Motor Vehicle Safety Standard No. 120 requires that the sum of the maximum load ratings of the tires on each axle be at least the gross axle weight rating. If you install passenger car tires on a truck or trailer under this standard, the load rating must be divided by 1.10 before comparing. Understand the difference between P-metric and LT tires in this guide.

4. Set the cold inflation pressure

Inflate the tires to the pressure indicated by the load and inflation table, not to the door placard unless the two match. Always set pressure when the tires are cold, meaning the vehicle has not been driven for at least three hours. Never exceed the maximum permissible inflation pressure marked on the tire sidewall, as defined in Federal Motor Vehicle Safety Standard No. 139. Use a reliable gauge and check the pressure after the tires have cooled.

5. Check the TPMS after adjusting

Vehicles under 10,000 pounds GVWR are required to have a tire pressure monitoring system that warns when pressure falls 25 percent below the vehicle manufacturer's recommended cold inflation pressure. After you raise the pressure for towing, the TPMS may still show a warning if the new pressure is lower than the placard value? Actually, the warning triggers when pressure is below the recommended pressure threshold. Since you are increasing pressure, the warning should clear, but if you have lowered pressure for other reasons, the TPMS will alert. Familiarize yourself with TPMS sensor types and their behavior.

6. Return to placard pressure after towing

Once you unhitch the trailer, the extra load is gone. Running the higher towing pressure on an unloaded vehicle can cause a harsh ride, uneven wear, and reduced traction. The load and inflation table shows that higher pressure also raises the tire's load rating, which you no longer need. After towing, let the tires cool and reset them to the placard pressure. This keeps the tire within its design envelope and avoids unnecessary wear. For more on pressure selection, see Max vs Recommended Tire Pressure.

What to pick for your towing setup

Questions

Where do I find the load and inflation table for my tires?

The table is published by the tire manufacturer, often in the owner's manual or on the tire manufacturer's website. It lists the load rating for each cold inflation pressure, from the minimum to the maximum permissible pressure. Some tire shops also have the tables printed in their service manuals.

Can I use the maximum pressure on the sidewall for towing?

You should not automatically use the maximum pressure. Use the pressure from the load and inflation table that provides the required load rating for your actual axle load. The maximum permissible cold inflation pressure is the upper limit, not a recommended setting. Exceeding it can reduce tire durability and may cause uneven wear.

Do I need to adjust pressure for the front tires when towing?

The load on the front tires usually changes less, but it can change depending on the hitch and how the trailer weight is distributed. Weigh the front and rear axles separately and set each axle according to its own load. Never use a single pressure for all four if the loads are different.

What happens if I don't raise the pressure when towing?

If the tire is underinflated for the load, its load rating may be insufficient. This can lead to overheating, increased flexing, and possible tire failure. Federal standards require that the vehicle maximum load on a tire not exceed the load rating at the inflation pressure you use.

Should I check pressure when the tires are warm after driving?

No. Always set cold inflation pressure. Driving heats the tires and raises pressure, so a warm reading will be higher than the actual cold pressure. Let the vehicle sit for a few hours, or check first thing in the morning before any driving.

Can I trust the TPMS to tell me if my towing pressure is correct?

The TPMS is designed to warn you if pressure drops 25 percent below the vehicle manufacturer's recommended cold inflation pressure. It does not tell you if the pressure is adequate for a heavier load. You must use the load and inflation table to set the correct pressure for towing.