How Do You Know What is the Proper Tire Inflation Pressure?

Not having the proper tire pressure in your vehicle's tires can lead to some very serious problems. This can be a safety hazard – to the point of becoming life threatening. Improperly inflated tires can go flat, and changing a tire on a busy road can lead to be struck by an inattentive, passing motorist. An overly inflated tire can burst, causing you to lose control of your car, possibly at high speed. Next to brakes, tires are the most important safety feature on your car.

Having improperly inflated tires can also decrease the life of the tire, becoming a financial hazard. According to the Michelin website, it is possible for a properly inflated car tire to lose 1 psi (pounds per square inch) of pressure each month. So keeping the proper pressure in your tires is really an important – and continual – maintenance item.

Since it is so important to make sure that you have the right pressure, how can you be sure what is best for your tires?

The proper pressure for your tires depends on the vehicle you drive. Even though a maximum pressure rating is often printed on the sidewall of the tire, this is NOT necessarily the pressure you should be using. Really, proper inflation is dependent on the car. This means that identical tires, mounted on different types of vehicles, will have a different recommended pressures.

Where can you find the proper inflation pressure for your tires? Check in the following places:

• You can find the correct pressure listed in the car’s owner manual.
• Some manufacturers put stickers with the pressure on the driver’s door jamb.
• Some cars have a sticker inside the fuel door. (This is to remind you to check the pressure when you fill up with gas).
• In the event you have lost your owner’s manual, the pressure may be printed on the inside of the glove compartment door.
• Never use the number imprinted on the sidewall of the tire. That is only the tire's maximum allowable pressure.

Remember that the vehicle manufacturer has determined this number based on a specific vehicle model matched with a particular size and style of tire, When you need to buy new tires, it is very important to buy the recommended tires. Since each car is matched with a specific type of tire, any good tire store can let you know what your options are.

Be aware that changing tires means that the listed pressures won't be valid. As an example, my pickup truck originally came with passenger car tires, although light truck tires were also an option. Because i need a sturdier tire, I have switched to the appropriate light truck tire for my vehicle, but I had to note the proper pressure since what is listed on the truck is for a different rating of tire.

Another thing to note is that some manufacturers will recommend different pressures for front and rear tires. Some might suggest different pressures for different types of driving - city versus highway driving, as an example.

With many cars, you can’t tell if your tires are properly inflated just by looking at them. For example, our Buick was designed for a smoother ride, so our tires usually look a little flat. Because of this, it is important to buy your own tire pressure gauge. The public gauges at gas stations have a history of being notoriously unreliable. Make sure to buy a decent quality gauge. When you think about what you spend on tires, a $10 to $20 gauge to protect them is a reasonable investment. If you ever have any doubts about the accuracy of your gauge, most tire stores will be happy to check it for accuracy.

You should try to check the tires when they are cold. The best time is first thing in the morning, before you drive even one mile on them. Tire pressure increases with temperature. For every ten degrees of temperature change, you get a change of 1 psi. To illustrate, if it’s 50 degrees in the morning and 80 in the afternoon, your tires will experience a 3 psi increase.

Realistically most of us are going to check and re-inflate our tires at a gas station. So, practically speaking, it is alright to check them any time of day, as long as they have been sitting for a few hours and after driving only a few miles to the local gas station.

Driving on your tires causes them to heat up and thus increases the operating pressure. The vehicle manufacturers have taken this into account. But if you check them when you have driven on them for a longer time and they have heated up, you will probably need to let air out of them to get back to the recommended pressure. This can lead to a dangerously under-inflated tire when they cool back down.

In addition to tire pressure, don’t neglect the valve stems or valve caps. Being made of rubber means they will deteriorate over time, just as your tires do. Always replace them when you buy new tires. Good quality valve caps can help stop leaks and keep dirt and water out of the valve stem. This is important since dirt or ice can cause the valve stem to fail, causing your tire to leak.

Finally: Don’t forget the spare! There’s nothing worse than being on the side of the road trying to change a flat tire - in heavy traffic or bad weather, usually - only to find that the spare has gone flat, too!