Tire Gauge

Air Pressure

The Benefits of Correct Air Pressure

Experts agree that keeping the correct air pressure in your tires is as important as giving your engine a tune-up. In fact, the economic benefits may be even greater. With the right amount of air pressure, your tires wear longer, save fuel, enhance handling, and prevent accidents. Failure to maintain the correct air pressure can result in poor gas mileage, reduce tire life, affect vehicle handling, and cause vehicle overloading. If you consider these factors, then the need to routinely check your tire pressure is even clearer.

Check Air Pressure Routinely

Because tires do so much without appearing to need attention, it's easy to forget about them. However, tires do lose pressure each day, through the process of permeation. In cool weather, a tire will typically lose one or two pounds of air per month. In warm weather, it's common for tires to lose air at an even higher rate. Tires are also often subjected to flexing and impacts that can diminish air pressure as well. So it's important to realize that refilling your tires is as important as refilling your gas tank. In fact, associating the need to refill your tires with the need for refilling your fuel supply can also be a useful reminder. Check the air pressure in your tires every other time you stop to fill up at the gas station. That interval will allow you to check your tire pressure consistently enough to maintain recommended air pressure. Another good time to check air pressure is when the tires are rotated. Many vehicles have different tire pressures on the front and rear axle, so remember to have this adjustment made. Also remember to have the pressure in your spare tire checked. The space-saver type spare requires a much higher air pressure level than other tires, and is virtually useless (due to overloading) at lower air pressure levels.

Where To Find Air Pressure Information

The correct air pressure may be found in the vehicle owner's manual or on the tire placard (attached to the vehicle door edge, doorpost, glove box door or fuel door). The placard tells you the maximum vehicle load, the cold tire pressures and the tire size recommended by the vehicle manufacturer. If you have trouble, visit your local America's Tire location for assistance.

Another valuable resource is tire load/inflation tables. Your local America's Tire should have a copy. Not only will this document tell you the correct tire pressure for stock sizes, but it will provide the information on optional plus sizes as well. A good example would be the findings on a Honda Civic with the stock size 185/65R-14. The recommended air pressure is 28 psi. Plus one size is 195/55R-15 with a recommended air pressure of 32 psi. Plus two size is 205/45R-16 with a recommended air pressure of 36 psi. Note how the air pressure increases with plus sizing to meet the load carrying capacity for the car.

Other Factors Change Air Pressure

In addition to routine air checks, other circumstances necessitate a visit to the air pump. Seasonal changes or altitude changes create a rise or drop in air pressure (for every 10 degrees change in temperature, tire air pressure changes 1 psi). Perhaps the most overlooked factor is vehicle loading for trucks and RVs. Since these vehicles can be configured and loaded in many ways, actual tire loads should be used to determine the proper inflation pressure. This is best determined by weighing the vehicle. Keep in mind that vehicle loading can change from trip to trip.

Sometimes a small nail, screw or other object will puncture a tire and then act as an inefficient plug. Air pressure drops slowly over a matter of hours or days, undetected by the driver. Your best defense in this circumstance is to be alert to the symptoms of this. Be aware of any pulling or vibration that seems unnatural. Listen for any ticking sounds, which will be especially audible at slow, parking lot speeds. If you detect this, get off the road and inspect the tires on the side of your vehicle where the pull, vibration or unusual sound is occurring. A bulging sidewall and/or excessively hot tire indicates a slow leak. Put on your spare tire and have your tire dealer repair the punctured unit. Ask the repair technician if any sidewall damage has occurred (a powdery residue inside the tire indicates this condition). If sidewall damage has occurred, you will need to have the tire replaced.

How To Check Air Pressure

Properly checking tire pressure requires an accurate air gauge. Many people believe that they can check air pressure just by looking at the tire and judging the sidewall appearance. Also, many people use air meters at service stations, which can be grossly inaccurate due to exposure or abuse. Invest in a quality air gauge. For trucks and RVs, use a dual-head inflation gauge that is calibrated up to 120 psi at 2 psi increments.

When checking your vehicle's tire pressure, make sure the tires are "cold". Cold air pressure means that the vehicle has not yet been driven one mile. Remember that driving on a tire increases its temperature and air pressure. If you must drive more than one mile for air, check and record the air pressure in all your tires before you leave. Once at the tire dealer, measure each tire's inflation again and then note the difference. Inflate the tires with low pressure to a level that is equal to the recommended cold pressure plus the difference at the higher temperature.

Air Pressure Illustration

In this example, add 3 psi in the right rear tire to match the other rear tire's warm reading. When the tire returns to cold pressure, it should end up at the recommended pressure.

Finally, after completing the pressure check, make sure that the valves and extensions are equipped with valve caps to keep out dirt and moisture. Remember to replace the valve assembly when you replace the tire. It's your best assurance against a sudden or consistent loss of air pressure.

Environmental Impact

How can routine air pressure maintenance impact our environment? Consider that fewer tires per year would end up in the landfills and scrap heaps that trouble our ecology. How many tires are we talking about? We estimate that most drivers lose from 10% to as much as 50% of tire tread life due to underinflation. That's a significant statistic. Now consider the extra fuel we burn to push cars along on soft, underinflated tires. Tires do require extra energy to roll if they are underinflated. While the statistics vary widely and can be somewhat inconclusive, the implications are staggering. Maintaining tire pressure may seem like a low priority in our busy daily routines, but it adds up to big environmental consequences. We must all take action to do the right thing.

Want to know more about better tire wear? See our articles on Balancing, Tire Rotation, and Alignment.

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