Tire Inflation Pressures

Your tires are arguably the most important part of your car. They provide a cushion to prevent your kidneys from feeling every little bump in the road. More importantly, they provide you with traction so that you, and not gravity and momentum, control which direction your car is moving.

Car tires that are under-inflated or over-inflated:

1.      Wear out faster

2.      Don’t provide full traction and control of the car

3.      Are more likely to blow out at highway speeds

4.      Reduce fuel economy

You should check your tire pressure once a week. That’s about how often most cars get washed, so get in the habit of checking the tire pressure at car wash time. If that doesn’t work for you, maybe you fill the gas tank once a week… check the tires too at that time then, or set a reminder on your phone or whatever else makes it easy for you to remember. Don’t forget to check the pressure in your spare too.

Most car owners check the pressure in their tires by simply looking at them. As you can imagine, this is a very ineffective way to check them. You should use a good tire pressure gauge. You can buy an inexpensive gauge at a car parts store, most stores like Walmart or Target, or even online.

There is a big difference between “inexpensive” and “cheap.” Cheap, poor quality gauges are inaccurate. I personally have one that displays a pressure reading that is 20 pounds off when compared against a known good gauge and tested on a device that has a known air pressure (the reservoir tank on my air compressor.)

There is a very good article on choosing tire pressure gauges published by Consumer Reports which can be found at https://www.consumerreports.org/cro/tire-pressure-gauges/buying-guide/index.htm

Tire pressure should be checked when the tires are cold. Air molecules, like most molecules, expand and contract with temperature. Tire pressure measured in a tire that has been driven for as little as 3 miles can read as much as 5 pounds higher than the pressure in a cold tire, which makes it difficult to get an accurate reading.

The proper tire inflation pressure is found on a sticker or placard found on the driver’s door edge or jam, or sometimes in the glove box. If you can’t find the placard, look in your owner’s manual.

The proper tire inflation pressure is based on several factors, including the weight of the car, the size of the tire, and its intended use (highway vs off-road, etc.).

Do NOT use the “Max Pressure” marking found on the tire itself. This “Max Pressure” it the maximum pressure the manufacturer of the tire has engineered the tire to hold. The same size tire your small car uses might also fit a larger car with a wider track and wheel-base, so the pressure requirements will be different. Inflating a tire to the Max Pressure rating will almost always result in an overinflated tire.

If you simply don’t feel like purchasing a gauge or dealing with the hassle of checking the pressure yourself, most tire shops will check and adjust the pressure in your tires for free. The Discount Tire store near my house offers this free service, and so does the Good Year store just down the road from them.

One last note on nitrogen filled tires:

I’m afraid that on this issue, I have to disagree with the Consumer Reports article I referred you to earlier. Consumer Reports states that the reason we use nitrogen is because it doesn’t leak out as fast as normal air (which is mostly nitrogen anyway…)

The real reason nitrogen is used is because it contains less moisture than normal air, and does not expand or contract as much as normal air does with changes in temperature. This means the air pressure remains stable under a wider variety of driving conditions, thus improving fuel economy and reducing tire wear.