The recommended tire pressure is the pressure established by the manufacturer of your car as the optimal air pressure for your tires. Running your tires at the correct pressure is important because it keeps you safe, cuts down your gas bill, and makes your tires last longer. Each vehicle has its own specifications for tire pressure, but most fall between 28 and 36 PSI (pounds per square inch).
The recommended pressure can either be found in your car’s operator manual or on a sticker on the inside of the post of the driver’s door (see picture). This is the pressure at which the car handles, brakes, and operates most smoothly and safely. Note that this specification refers to the pressure as measured when the tire is cold (called cold pressure). If you’ve driven your car or it has been sitting in the sun, the resulting heat could raise your tire’s pressure by several PSI.
To do an air pressure check on your tires, you’ll need a tire pressure gauge. You insert this tool over the valve of your tire, and it shows you the pressure in PSI either on a dial or on a telescoping rod that the pressure pushes out of its casing. For an accurate reading, make sure you hold the tip of the gauge firmly over the valve until no air is hissing out around the edges. Again, remember that temperature can affect the pressure in your tires, so whenever possible it’s best to take a cold reading before driving and when the tire is not exposed to sun or heat.
Be careful not to confuse the recommended pressure with the maximum pressure. The recommended pressure is the one you should use when filling your tires, and, as explained above, you can find on your doorjamb or in your owner’s manual. The maximum pressure, on the other hand, is usually stated on the sidewall of the tire itself in small print near the tire’s bead (where the rubber abuts the rim). This measurement is provided by the tire manufacturer rather than the car manufacturer and is the maximum amount of pressure the tire can safely withstand.
Your tires’ max PSI almost always exceeds the recommended pressure. It isn’t advisable to fill your tire to this pressure for everyday driving. At max PSI, your car does not handle as well, braking is impaired, and you could risk dangerous blowouts. Over-inflation can also cause the center of your tire’s tread to wear out prematurely and reduce the lifespan of your tires. You may want to use the max pressure on a temporary basis if you are hauling especially heavy load or towing something.
Most manufacturers do not state a minimum tire pressure, per se. The recommended value is the amount of air that a tire needs for a car to handle properly and safely, and anything under that value is not recommended, so functionally the optimal value is also the minimum. Under U.S. law, vehicles are required to be equipped with tire pressure monitoring systems (TPMS) that warn the driver when tire pressure falls below 25 percent of the recommended PSI. This is considered severe under-inflation, but less drastic pressure drops are still considered moderate or mild under-inflation, and they and can still have negative consequences.
If your tires are inflated to a pressure that is below the recommended PSI (as shown in the manual or on the driver’s side doorjamb), your car will not operate safely. Under-inflation can cause the tire to heat up excessively, which can make the tread pull away from the body of the tire. If this happens on the highway, it could lead to a blowout and a serious accident. There are also financial reasons for making sure your tires aren’t under-inflated. A low tire has more rolling resistance, which means the car has to work harder to move down the highway and consumes more fuel. Well-inflated tires are going to save you money at the pumps. Low tires also wear more quickly and unevenly, so you will have to replace them more often.
A tire pressure monitoring system (TPMS) uses either a direct sensor inside your valve stem or a combination of both software and other existing sensors in your vehicle to let you know when your tire pressure is outside of a safe range of pressures. If the pressure falls below the legally specified limit (25% of recommended pressure) an indicator light shaped like the letter U with an exclamation point inside it (representing the cross-section of a tire) will light up on the dashboard. When you see this TPMS light on you should immediately check your tire pressure and make any necessary adjustments.
If you have further questions about tire pressure or any other aspects of your tires, find your nearest tire dealer to get some advice.
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