How to Check Tire Pressure: Step-by-Step Guide

Tire pressure is one of the most overlooked aspects of vehicle maintenance, yet it affects nearly everything about how your car performs. Under-inflated tires increase braking distance, reduce fuel economy by up to three percent, cause uneven tread wear, and are more susceptible to blowouts at highway speeds. Over-inflated tires reduce your contact patch with the road, resulting in less traction and a harsher ride.

Checking tire pressure takes about two minutes and requires a single inexpensive tool. There is no reason not to do it monthly.

What You Need

• A tire pressure gauge -- digital or stick-type, available at any auto parts store for under ten dollars
• An air compressor -- available at most gas stations, or you can buy a portable 12-volt compressor that plugs into your vehicle's power outlet

Finding Your Correct Tire Pressure

Your correct tire pressure is listed in two places:

• The sticker on the inside of the driver's door jamb
• Your owner's manual

Do not use the number printed on the tire sidewall. That number is the maximum pressure the tire can safely hold, not the recommended pressure for your vehicle. The recommended pressure is determined by the vehicle manufacturer based on the vehicle's weight, suspension, and handling characteristics. It is typically between 30 and 35 PSI for most passenger vehicles.

Some vehicles specify different pressures for front and rear tires. Check the sticker carefully and fill accordingly.

Step-by-Step Instructions

1. Check When Tires Are Cold

Tire pressure increases as tires heat up from driving. For an accurate reading, check pressure when the tires are cold -- either first thing in the morning or after the vehicle has been parked for at least three hours. If you must check after driving, expect readings to be two to four PSI higher than the actual cold pressure.

2. Remove the Valve Cap

Unscrew the small cap from the tire's valve stem. Set it somewhere you will not lose it -- a pocket is fine.

3. Press the Gauge Firmly

Press the tire pressure gauge squarely onto the valve stem. You may hear a brief hiss of air as you seat the gauge. If air continues to hiss, the gauge is not seated properly -- reposition it until you get a clean reading.

4. Read the Pressure

Digital gauges display a number directly. Stick gauges push out a white bar marked with PSI numbers. Read the number where the bar stops. Note the reading and compare it to the recommended pressure for your vehicle.

5. Add or Release Air

If the pressure is too low, add air using a compressor. Add air in short bursts, checking the pressure frequently. It is easy to over-inflate, so go slowly. If the pressure is too high, press the small pin in the center of the valve stem briefly to release air in controlled bursts. Check after each release.

6. Replace the Valve Cap

Screw the valve cap back on. It keeps dirt and moisture out of the valve mechanism. A missing cap will not cause immediate problems, but it can lead to slow leaks over time.

7. Repeat for All Tires

Check all four tires and the spare. Yes, the spare. A flat spare tire is useless when you need it. Compact spare tires typically require 60 PSI -- significantly more than your regular tires.

TPMS Is Not Enough

Vehicles made after 2007 in the United States have a Tire Pressure Monitoring System (TPMS) that illuminates a warning light when pressure drops significantly below the recommended level. However, TPMS typically does not alert you until pressure is 25 percent below the recommendation. At that point, you have already been driving on under-inflated tires long enough to cause extra wear, reduced fuel economy, and compromised handling. Manual checks catch problems well before TPMS does.

Seasonal Pressure Changes

Tire pressure changes with temperature. For every ten-degree Fahrenheit drop in ambient temperature, tire pressure drops by roughly one PSI. This means that tires inflated to 35 PSI in summer may read 30 PSI or lower on a cold winter morning. Check pressure more frequently during seasonal transitions, especially in fall and early winter.