Before you can check or set your tire inflation pressure, you have to know where to locate the tire pressure that is recommended for your vehicle. Since there are generally a wide variety of tire brands and sizes that can fit any given vehicle make and model, vehicle manufacturers predetermine the tire inflation pressure that is best for each specific vehicle.
While the tire's sidewall does identify a maximum cold inflation pressure, it is not necessarily the correct pressure to use for your vehicle. Your vehicle load might be different than that of other vehicles that use the same tire, so the tire pressure listed on the sidewall could be inaccurate for your specific vehicle. In fact, almost all vehicle manufacturers specify a recommended tire inflation pressure that is less than the tire pressure listed on the tire's sidewall.
You should check the manufacturer's tire inflation recommendation and use that as the basis for your inflation pressure. So where do you find the manufacturer's recommendation?
First, check the vehicle's owner's manual, because many manufacturers list the recommended tire pressure there. In some cases, the manufacturer may also specify alternate pressures based on load and/or speed. In fact, new vehicle owner's manuals must address these five subjects:
Regarding Vehicle Load Limits, manufacturers are required to identify the vehicle's load capacity with the following sentence: "The combined weight of occupants and cargo should never exceed XXXX pounds." For safety, it is extremely important to stay below the maximum vehicle load rating. For example, it would be quite possible to exceed a vehicle's load capacity if you were to carry additional passengers and extra cargo, such as luggage, in a rooftop carrier and/or the trunk space.
In addition to the owner's manual, you should also be able to find tire inflation information on the vehicle's tire information placard. Beginning in 2003, vehicle manufacturers were directed to standardize the format and placement of tire information placards. The tire information placards identify the vehicle weight capacity, the OE (Original Equipment) tire sizes (including the spare tire) and the recommended inflation pressures for the tires. On new vehicles, the placard must be located on the "B-pillar", which is the driver's side doorjamb. For vehicles that do not have a B-pillar, the placard should be attached to the rear edge of the driver's door, unless it is too narrow, in which case it should be placed on an inward-facing surface next to the driver's seat. On older vehicles, placards can also be found in other locations inside the vehicle:
Once you have located the recommended cold tire inflation pressure and vehicle load in either the owner's manual or on the tire information placard, the next thing to understand is how temperature can affect the inflation reading. For complete details, see our article Tire Inflation Pressure and Temperature. For now, suffice it to say that the tire inflation pressure should be checked first thing in the morning when the tires are at their coldest- before the vehicle has been driven, before the tires have been in direct sunlight, and before the temperature rises.
Also, you need to use a proper quality tire gauge to measure the inflation pressure. Do not rely on a visual check because it is not possible to accurately measure tire inflation pressure with only a visual inspection.
In summary, all tires, regardless of size, will experience a decrease in the designed performance (load capacity, traction, handling, and durability) if the tire inflation pressure is either too low or too high. Make sure you achieve optimum performance and safety of your tires by maintaining the proper recommended tire inflation pressure(s).