How Much Air Do Your Tires Need? A PSI Guide

Find your vehicle's recommended tire pressure

The single most important number for your tires is the cold inflation pressure set by the vehicle manufacturer. This value is based on the vehicle's weight, ride characteristics, and tire size. You will find it on a placard, usually on the driver's side door jamb or inside the glove box, as well as in the owner's manual. The U.S. Department of Energy's fueleconomy.gov site explicitly says to use the placard and not the maximum pressure printed on the sidewall.

The pressure printed on the tire sidewall is the tire's maximum permissible inflation pressure, defined by the tire manufacturer under federal standards. That is the highest cold pressure to which the tire may be inflated, not the recommended operating pressure for your car. Using the sidewall number will almost always over-inflate the tire for daily driving. Related guides: tire sidewall markings explains the markings, and tire inflation pressure chart gives more context.

How to check tire pressure correctly

Check pressure when the tires are cold, meaning the vehicle has been parked for at least three hours or driven less than a mile. That matches the regulatory definition of cold inflation pressure used in Federal Motor Vehicle Safety Standard No. 139. Remove the valve cap, press a tire gauge firmly onto the valve stem, and read the measurement. Compare it to the placard pressure.

Add air if the reading is low, or release air if it is high. Recheck after adjusting. Repeat for all four tires, including the spare if your vehicle has one. Doing this monthly is a good habit, though the exact interval is up to you. The fuel economy site notes that properly inflated tires are safer and last longer. For a deeper look at how pressure affects wear, see tire tread wear causes.

• Park the vehicle and let tires cool.
• Remove the valve cap from the first tire.
• Press the gauge firmly onto the valve stem until the reading stabilizes.
• Record the pressure and compare it to the placard value.
• Add or release air to match the placard, then recheck.
• Replace the valve cap and repeat on all four tires.

What happens when pressure is too low

Under-inflation is the most common pressure problem. According to fueleconomy.gov, under-inflated tires can lower gas mileage by about 0.2% for every 1 psi drop in the average pressure of all tires. That same source notes that properly inflated tires are safer and last longer.

Low pressure also reduces the tire's load capacity. Federal Standard No. 110 requires that the vehicle normal load on a tire not exceed 94 percent of the load rating at the recommended cold inflation pressure. When pressure drops below that, the tire may be overloaded even under normal driving, leading to heat buildup and possible structural failure. The TPMS is designed to warn you when pressure falls to about 25 percent below the recommended value, per Standard No. 138. See do I need tire pressure monitoring system for more.

What happens when pressure is too high

Over-inflation is less common but still a problem. More air than recommended makes the tire stiffer, which reduces the contact patch with the road, so the tire rides harsher and can wear unevenly in the center. While a slightly higher pressure may improve fuel economy momentarily, it also reduces grip, which is especially dangerous on wet roads. The placard pressure is the manufacturer's balance of ride, handling, and wear.

The sidewall lists the maximum permissible inflation pressure, and you should never exceed it. For a tire marked "Max. pressure 44 psi," setting it to 44 is a mistake for most passenger cars; the placard will typically specify a lower value. Remember that the federal standards define maximum permissible inflation pressure, not the recommended operating pressure. For more on how pressure affects your tire's shape and service, see tire construction types.

What about tire pressure monitoring systems?

Since the 2008 model year, passenger cars and light trucks sold in the United States must have a TPMS. Standard No. 138 requires that the system illuminate a warning within 20 minutes when the pressure in one or more tires falls to 25 percent below the recommended cold inflation pressure or below a specified value, whichever is higher. The system also warns when the TPMS itself malfunctions.

A TPMS does not tell you the current pressure; it only warns you at that threshold. So it's still important to check pressure manually, especially because pressure changes with temperature and normal leaks. The warning light means you should inflate the tire to the placard pressure as soon as possible. If the light stays on after adjusting, have the system inspected. Learn more at do I need tire pressure monitoring system.

Adjusting pressure for load and towing

Many vehicles, especially trucks and SUVs, have different recommended pressures for partial load and full load conditions. The placard may list two values, such as "normal load" and "maximum load". This is because the load rating of a tire increases with inflation pressure, up to its maximum permissible pressure. Federal Standard No. 110 requires that the vehicle's tires have sufficient load capacity for the GAWR, so the manufacturer's pressure for heavy loads is essential when carrying cargo or towing.

For light trucks, you may see tires with LT (light truck) marking. These have higher load ratings and require higher pressures than passenger car tires. For example, an LT tire might be inflated to 50 or 80 psi, but the exact number is still set by the vehicle maker. Never exceed the max pressure on the sidewall. For more on load ranges, see what is tire load range and tire load capacity chart. To pick the right tire for your use, see our best light truck tires.

What to pick for your use

Questions

What is the correct tire pressure for my vehicle?

Use the value printed on the placard on the driver's side door jamb or in the glove box. This is set by the vehicle manufacturer, not by the tire maker, and it is always listed in the owner's manual as well. The number on the tire sidewall is the maximum permissible inflation pressure, not a recommended setting.

How often should I check tire pressure?

Check at least once a month and before long trips. Pressure changes with temperature and normal leaks, so a monthly check is a good habit. Also check whenever the TPMS warning light comes on.

Why does my TPMS light come on?

Under federal Standard No. 138, the TPMS must trigger a warning when the pressure in one or more tires falls to 25 percent below the recommended cold inflation pressure or below a specified value, whichever is higher. It is telling you to check and inflate the tires to the placard pressure.

Can I use the pressure shown on the tire sidewall?

No. The sidewall shows the maximum permissible inflation pressure, which is the highest cold pressure the tire can safely handle. For normal driving, you should always follow the vehicle placard pressure, which is almost always lower than the sidewall maximum.

Should I adjust tire pressure when towing or carrying heavy loads?

Yes. The placard may list a separate pressure for full load. If you are towing or carrying a heavy load, inflate to that higher recommended value. Never exceed the maximum pressure printed on the sidewall.

Does tire pressure affect fuel economy?

Yes. Under-inflation can lower gas mileage by about 0.2% for every 1 psi drop in average pressure across all tires, according to fueleconomy.gov. Properly inflated tires are also safer and last longer.