Checking Tire Inflation Pressure

Regardless of its size, every tire's load capacity, durability, traction and handling is dependent on using the right inflation pressure for the application. Since both too little and too much inflation pressure sacrifices some of the tires' performance, maintaining the "right" inflation pressure is very important.

While a wide variety of tire sizes are available to fit the many different vehicles in use today, almost every tire size can be used on more than one vehicle. Therefore it is the vehicle manufacturers that ultimately determine the tire inflation pressures they believe best fine-tune the tires' capabilities to their specific vehicle makes and models.

The pounds per square inch (psi) pressure number branded on the tire's sidewall identifies the maximum cold inflation pressure that specific tire is rated to hold. However, the tire's maximum pressure is not necessarily the correct pressure for every vehicle upon which the tire can be used (almost all vehicle manufacturers' recommended tire inflation pressures are less than the tires' maximum pressure).

Therefore when checking and adjusting tire inflation pressures, the "right" inflation pressures are those provided by the vehicle manufacturer, not the "maximum" inflation pressure branded on the tire's sidewall. The vehicle manufacturer's pressure recommendation can be found on the vehicle's tire information placard label, as well as in the vehicle owner's manual.

Beginning in 2003, vehicle manufacturers were directed to place tire information placards in a standardized location and follow a common format. The tire information placards identify the Original Equipment tire sizes and inflation pressures (including the spare), along with the vehicle weight capacity.

The placard on new vehicles must now be located on the driver's side doorjamb (called the "B-pillar"). If a vehicle does not have a B-pillar, then the placard is to be placed on the rear edge of the driver's door. And if the vehicle does not have a B-pillar and the driver's door edge is too narrow, the placard is to be affixed on an inward facing surface next to the driver's seating position.

In addition to providing the Original Equipment tire size and recommended inflation pressure, vehicle manufacturers must also identify vehicle load capacity with the following sentence: "The combined weight of occupants and cargo should never exceed XXXX pounds."

NOTE: Adhering to this vehicle load capacity information is important. For example, our calculations indicate it would be easy to exceed a five passenger SUV's rated vehicle weight capacity by carrying additional passengers in the vehicle's rear "cargo area" and placing all luggage on a rooftop carrier.

Additionally, new vehicle owner's manuals must also address the following five subject areas: tire labeling, recommended tire inflation pressure, glossary of tire terms, tire care, and vehicle load limits. Vehicle manufacturers can also list alternate tire pressures based on load and/or speed in the owner's manuals.

For vehicles produced between 1968 and 2003, the original tires size(s) and inflation pressures (including the spare) are listed on a vehicle placard (sometimes alternate pressures based on load and/or speed conditions are also provided).

Earlier placards can typically be found on:

• The driver-side door or doorjamb
• Rear passenger doorjamb of Ford sedans
• Fuel filler door
• Glove box or center console door
• The engine compartment

Many manufacturers also list the recommended tire pressure in the vehicle's owner's manual (sometimes along with alternate pressures based on load and/or speed).

One final note, tire pressure must be checked with a quality air gauge as the inflation pressure cannot be accurately estimated through visual inspection.