Are Your Tires Underinflated?

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Vintage photo of a man changing a tire
Don’t be this person.

How often do you think about the air in your tires? If you allow your vehicle’s tires to lose too much air pressure, you could be in for a rough ride, or a deadly one.

738 peopled died in tire-related crashes, according to the National Highway Transportation Safety Administration (NHTSA), which credits underinflated tires and overloaded vehicles as a major cause of tire failure.

Yet, a meager seventeen percent of drivers know how to properly check tire pressure, while half don’t know where to find a tire’s recommended pressure level, according to a survey by the Rubber Manufacturers Association (RMA), which represents tire manufacturers.

Significantly underinflated tires are dangerous because they can overheat, says Dan Zielinski, RMA’s senior vice president for public affairs. “Heat is the enemy of a tire. When tires are under inflated, heat builds up in the tire that can cause damage that may lead to tread separation. When that occurs, loss of vehicle control may occur.”

Check your tire pressure once per month. They will naturally deflate over time, as well as after encountering potholes or striking curbs, or when the weather turns cool.

To check and adjust tire pressure:

Purchase a tire pressure gauge

Don’t rely on the gauges attached to gas station air pumps. “Gas station inflation systems take a good deal of abuse, which can affect the accuracy,” says Zielinski.

Small, portable gauges are sold at auto parts stores and many general-merchandise retailers. They and cost anywhere from $5 to $50, but a good one can be had for under $15, according to Consumer Reports.

Let your tires cool down

Wait until your vehicle has been sitting still for at least three hours, because your tires have to be “cold” in order for you to obtain an accurate reading. This has nothing to do with the weather or outdoor temperature. It means that, if a tire that has been recently driven, the air inside will have warmed up, expanded, and temporarily increased its pressure.

Get the numbers

Look for your vehicle’s recommended tire pressure in the owner’s manual or on the driver-side door, glove compartment or trunk lid. The number will be next to the acronym “psi,” which means pounds per square inch. (It will also be listed metrically as “kPa, or kilopascals, for drivers who use the metric system.)

Don’t use the “psi” number listed on the tire’s sidewall. It lists the maximum — not the recommended — pressure, according to Zielinski. This is because you also want to avoid overinflating tires. “Over inflated tires have a smaller contact patch with the road, which affects handling,” he says. “They also will wear out the center of the tread faster and will be more susceptible to road hazard damage.”

Check your tires

On each tire — including the spare — unscrew the valve cap from the stem, which is located on the side of the tire. Fit the gauge into the stem. If you hear a hissing sound, which is air escaping, adjust the fit until it stops. Then read the pressure number on the gauge.

Adjust the pressure

If the number on the gauge is lower than recommended, drive to a nearby service station and add enough air to bring it up to the recommended number — but no higher. Don’t try to compensate for warm tires by overinflating, which creates a safety hazard. Instead, perform a second check later, after the tires are cold again. Then return to add more air if needed.

On the other hand, if the number on the gauge is too high, just press the valve stem gently — you can use the side of the gauge for this — to let some air out.

On-Board Sensors

Starting with the model year 2008, all cars, trucks and light vans are required to have a Tire Pressure Monitoring System (TPMS). Using sensors, it automatically detects when a tire is significantly below recommended pressure. Then it notifies the driver by lighting up an indicator on the dashboard.

The sensors won’t know whether the tire just needs some more air or has a potentially dangerous leak that could cause a flat. So, the Tire Industry Association recommends having your tires checked by an industry professional whenever the indicator light turns on.

However, you should continue to monitoring your tires manually, even if your vehicle has TPMS. “It only provides a warning when tire pressure drops 25%, which is a significant loss of pressure,” says Zielinski.

David Arv Bragi, profile picture

David Arv Bragi is a multidisciplinary journalist with experience in health, safety, personal finance, technology, arts and cultural topics. He is also a former team leader and volunteer in community/tower emergency response teams. He currently lives just outside of Bellingham, Washington.