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For most passenger cars, the correct tire pressure is somewhere between 28 and 36 PSI. However, depending on the size and style of the tire, this can vary quite a bit between cars. Also, if a different size and style of tire is put on a passenger car -- for instance, if someone upgrades to performance tires on a car that came with standard tires from the factory -- the proper tire inflation may actually change.
Proper tire inflation is extremely important for many reasons. Tires that are inflated to the correct pounds per square inch, or PSI, wear more evenly and last longer. Also, the car will get better gas mileage. Many people, however, are confused about what the correct tire inflation is for their vehicle.
There are a couple of ways to find out what the correct tire inflation is for your vehicle. The best way is to find out what the tire manufacturer recommends. Sometimes, tires state a recommended PSI on the sidewall; however, it is important to note that this is not the same as the maximum PSI, which may also be stated on the sidewall. A tire should never be inflated to the maximum PSI, as you will be risking a blowout.
If the recommended PSI is not listed on the outside of the tire, you should be able to get this information by calling the store that sold you the tires. Make it a point, whenever you buy new tires, to ask them to write the manufacturer’s recommend PSI on the paperwork. Otherwise, you or a mechanic might incorrectly inflate the tire.
Although it is best to follow the manufacturer’s guidelines, you can usually find out what tire pressure the car manufacturer recommends. This information is generally printed on a sticker somewhere inside your car: for instance, in the door jamb, in the glove box, or under the hood. This information can also be found in the owner’s manual. However, keep in mind that the proper tire inflation can vary between tire manufacturers, so even if you kept the same size tires on your car, the tire pressure given by the car manufacturer may not be correct.
Tire pressure should always be checked first thing in the morning, before you drive your car anywhere. The reason for this is that tire pressure is dependent on temperature, and driving heats up the tires. When you drive, the tire inflation actually increases. This is why you should never fill your tires to the maximum tire pressure stated on the outside of your tires -- when they warm up, the inflation will rise above the maximum, and you may experience a blowout.
Another reason why you should not over inflate your tires is because they will wear unevenly. Too much tire inflation will cause the tread to wear a stripe right down the middle, not to mention it will also reduce contact with the road, and put you at risk for an accident. Too little tire pressure will cause the sidewall to make contact with the road, and since the sidewall has no tread on it, you will rapidly wear it out, or even cause a blowout. Additionally, improper tire inflation will reduce your gas mileage by about three percent on average.
If the tire states Max PSI of 44, the sticker on the door recommends 35psi. Does the dealer want me to buy his tires more frequently, by reducing my tire pressure with each check up?
I remember when tire pressure information was always on the glove compartment door, but these days, it's usually on the rear driver's side door, for US-built cars.
This information is also almost always in the car's owner's manual. If the manual disappears, they can usually be found online, and if the car is less than 10 years old, often on the carmaker's website. For instance the Ford Motor Company has many back editions of owner's manuals on its site. Very handy if yours goes missing.
Proper tire inflation will keep a driver safer, because the tires are performing properly, but will also improve gas mileage. Under-inflated tires are a leading cause of decreased mpg.