Tire Pressure and Everyday Tire Care

Open the driver door and look at the edge of the door or the pillar it closes against. The placard lists the original tire size and the cold inflation pressure for the front and rear, which are sometimes different. That is the number your vehicle maker chose for load, handling and wear.

Why not the sidewall number?

The number on the sidewall is the tire's maximum cold pressure, not the pressure your vehicle asks for. Filling to it makes the ride harsh, shrinks the contact patch and wears the center of the tread. It is a ceiling, not a recommendation.

Special cases

• Towing or full loads: some owner manuals list a higher pressure for heavy loads.
• LT tires on trucks: light-truck tires often run higher pressures than passenger tires.
• Different tire size than original: a plus size or a different load type may need a different pressure. We work it out from load tables when we install them.
• Temporary spare: a compact donut is often inflated to about 60 psi, and that figure is printed right on the spare next to its speed limit, commonly 50 mph. See spare tire service.

Check with the tires cold: before the first drive of the day, or at least 3 hours after the car was parked. Remove the valve cap, press the gauge on firmly, read it, and add or release air until it matches the placard. Put the cap back on. Do all four tires, plus the spare if you can reach it.

1. Park on level ground before driving for the day.
2. Read the placard for front and rear pressures.
3. Check each tire with a gauge you trust.
4. Add air in short bursts and recheck.
5. If a tire is hot from driving, do not let air out to hit the number. Recheck later when it is cold.
6. Replace every valve cap.

A tire can lose a good amount of air before it looks low, especially with low-profile or run-flat tires. A gauge is the only way to know. Federal rules require the TPMS light to come on once a tire sits 25 percent or more below the placard number, so it is a late alarm rather than a replacement for a monthly check.

Low pressure lets the tire flex too much. It builds heat, wears the outer edges, hurts fuel economy and steering response, and in extreme cases can lead to a failure at freeway speed. High pressure makes the tire stiff, wears the center, and reduces grip, especially on wet roads.

The fuel economy site (opens in a new tab) run by the U.S. government lists proper inflation among its fuel-saving tips. Our wear patterns page shows how pressure mistakes look on the tread.

While you check pressure, take a minute to look at each tire. You are looking for low tread, objects in the tread, cracks, bulges and uneven wear. Catching a nail early often means a repair instead of a new tire, and catching a bulge early can prevent a blowout.

Monthly look

• Tread depth: wear bars are molded across the bottom of the grooves at 2/32 inch, which is where NHTSA advises replacing a tire. If you want wet grip, plan on new rubber nearer 4/32 inch. California Vehicle Code 27465 only requires 1/32 inch in any two adjacent grooves, so street legal and rain ready are different numbers.
• Objects: nails, screws and stones stuck in the tread.
• Sidewalls: cuts, bulges, scrapes from curbs, and cracking.
• Wear pattern: one edge worn more than the other.
• Valve caps: present and snug.

Every few months

• Rotate on your maker's schedule, which for most vehicles lands between 5,000 and 8,000 miles or at each oil change.
• Check the spare.
• Read the date codes. Our date code guide shows how.

If anything looks off, we check it during any visit and show you what we found.

Warm air expands, so tire pressure rises as tires heat up from driving and from hot pavement. That is why you set pressure cold. The rule of thumb works both ways: pressure moves about 1 psi for every 10 degrees Fahrenheit the outside temperature changes. A tire set cold in the morning can read several psi higher by afternoon, and that rise is normal and already built into the placard number.

What to avoid:

• Letting air out of a hot tire to match the placard. It will be low once it cools.
• Setting pressures in the afternoon sun after a freeway drive.
• Ignoring slow leaks in summer that show up as a TPMS light on the first cool morning.

For more on driving through Inland Empire heat, see seasonal tire tips.

The biggest one is trusting how the tire looks. A radial tire can be down a lot of pressure and still look almost normal, especially on an SUV. The second is checking right after driving, when warm air makes a low tire read fine. A gauge on a cold tire is the only reliable combination.

Other common mistakes:

• Filling to the sidewall number: that is the tire's maximum, not the pressure your vehicle needs.
• Trusting the air machine gauge: those gauges take a beating. Carry your own and compare.
• Letting air out on a hot afternoon: the reading rose from heat and drops back as the tire cools.
• Forgetting the spare: a donut runs far more air than the road tires, and its own sidewall prints the number.
• Setting all four the same: some vehicles list different front and rear numbers.
• Waiting for the dash light: it is an alarm, not a monitor. A healthy tire seeps about 1 psi a month on its own, and that drift never trips it.

A monthly check at home is quick. If one tire keeps needing air, the cause is usually a puncture, a valve stem or a bead leak, and it is worth finding before it turns into a flat.