Tire pressure is the amount of air in your tire, which is usually measured in pounds per square inch (PSI). Since it is actually the air inside your tire that bears the weight of your car, getting this aspect of maintaining your car right is key. If your tires are under-inflated, your vehicle’s handling and braking could be thrown off, and also the sidewalls could break down, leading to a blowout. Over-inflated tires are also at greater risk for blowouts, and they can cause your vehicle to lose traction. In addition to the safety concerns, tires with the wrong amount of air in them are likely to wear out much faster than those with the correct pressure, so you’ll have to shell out money for new ones much sooner. Under-inflated tires also reduce the gas mileage of a car or truck. It’s safe to say that incorrect tire pressure is not going to do wonders for your bank account. As you can see, there are plenty of reasons for maintaining the right tire pressure, so let’s take a look at how to check your tire pressure it in 7 steps.
First you need the right equipment: a pressure gauge and an air compressor. There are two basic types of tire gauges. The most common is the “stick” type gauge, which has a casing with a rod inside it that slides out and gives you a pressure reading when you fit the tip over the valve. There are also dial type rods that give you the reading on something similar to a clock face. After reading to pressure, you’ll also need a compressor to fill any low tires, although in a pinch you could use a manual pump (be ready to break a sweat). Both of these pieces of equipment can often be found at gas stations.
Many drivers make the mistake of looking on the tire’s sidewall to find the right pressure. The pressure stated on the tire itself is the maximum pressure, which is not the optimal pressure for your vehicle. The recommended pressure for your car or truck is given by the manufacturer, as it depends on the specific characteristics of your vehicle. You can find this specification (given in PSI) on a plate inside the driver’s side doorjamb or in your owner’s manual. Note that this value will be the cold pressure, which can be measured before driving on your tires or exposing them to the heat of the sun. Hot air expands, so hot tires will show a higher pressure reading than cold ones.
Now that you have your tools and you know the right pressure, find the valve, which is a little tube poking through the wheel (the metal part the tire is mounted on). It will usually have a small cap on it. Unscrew the cap and save it in a safe place so you can screw it back on later.
The tip of your gauge has a round, flat face on one side with a smaller round protrusion inside it. You need to fit this face firmly over the top of the stem and push down. If air is hissing out around the edges, adjust the gauge until it forms a seal around the valve stem. Air from inside the tire will rush into the gauge and push out the indicator rod (or move the needle on the dial) to show the tire’s current pressure.
If your tire is low, you’ll need to air it up with the compressor. At gas stations, compressors are often fitted with a tip that looks somewhat like a pistol, with a “trigger”—a lever similar to the ones fire extinguishers are equipped with. Fit the tip of the “pistol” over the valve, and pull down the lever to start the flow of air into the tire. You should hear the muffled sound of air entering, like the noise of a balloon when you are blowing it up. If you hear sharp hissing sounds, this means the compressor tip isn’t seated right on the valve and air is escaping out the sides instead of going into the tire.
As you’re airing the tire up, frequently re-check the pressure using the gauge as described in step four so you don’t overfill your tire. Once you reach the recommended amount, you can screw the valve cap back on and move on to the next tire.
If you put too much air into your tire with the compressor or you found that your tire was well above the recommended pressure when you originally checked it with the gauge, you’ll need to remove air. You can use the tire gauge to do this. The tip of the gauge has a small protrusion opposite the flat face used to check pressure. Use this protrusion to depress the small pin with a round head that’s inside the valve stem on the wheel. This releases air from the tire. If you’re successful, you’ll hear air rushing out of the tire. Continue releasing air and checking the pressure until you have reached the recommended PSI reading. Remember, recommended PSI values are for when the tires are cold, so if the tires are hot and a few PSI over the recommendation, you don’t need to release air.
The recommended tire pressure is a specification given by the manufacturer based on how much the vehicle weighs, how much weight it is designed to carry, and other factors like suspension, performance, and handling. You can find this value on a plate inside the post of the door on the driver’s side or in your owner’s manual. This specification is not to be confused with the tire’s maximum pressure rating, which is molded onto the tire itself. This maximum rating is provided by the tire manufacturer and usually exceeds the recommended pressure.
Starting in 2008, all new cars in the U.S. are required by law to be equipped with a tire pressure monitoring system (TPMS) as a safety feature. These systems use a piece of hardware attached to the back of the valve stem or a combination of sensors in other systems to alert you when your tire pressure is severely low. When this happens, a light shaped like a horseshoe with an exclamation point in it lights up on your dashboard so you know you need to check and fill your tires.
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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