- Only 17% of drivers are "tire smart," or know how to properly check tire pressure.
- Only 50% of drivers know where to find the correct inflation pressure for their vehicle: The label on a vehicle's driver-side door or owner's manual. Fifty percent of drivers wrongly believe that the correct pressure is listed on the tire sidewall.
- One out of three drivers don't know that tires should be checked "cold" before driving. One of the biggest mistakes you can make is checking tires after driving. As tires roll, they warm up, which causes the pressure to increase. This could yield a false tire pressure reading.
- Four in 10 drivers believe they can tell if a tire is under-inflated just by looking.
- Two out of three drivers do not check the tire pressure in their spare tire.
Having your tires inflated to the correct pressure is critical for alignments, TPMS (Tire Pressure Monitor System) service, and maintaining fuel efficiency. If you are not filling your tires to their correct tire pressure, you could be setting yourself up for failure, so never underestimate the value of proper tire inflation.
Ambient temperature affects tire pressure on every tire. For every increase or decrease of 10°F of ambient temperature, tire pressures will change about 2%, or about 1 psi (pounds per square inch) for the average passenger vehicle tire.
If a tire's pressure was set on a summer day when it is 90° F and it is now 40° F, the tire will have lost 4-5 psi just due to changes in temperature. On some vehicles, this could cause the TPMS light to illuminate. It also works the other way around. If a tire was inflated at 40° F and the outside temperature is now 90° F, the tire could now be over-inflated.
Always take outside and indoor temperature into consideration when setting inflation. For example, a 40° F discrepancy may require you to add 3 to 4 psi (40° F = 4 psi) over the placard pressure to account for cooling when the vehicle has been parked outside. If this is done correctly, the cool pressure should be close to the specified cold pressure. As a general rule, never set the tire pressure below the specified placard value regardless of tire temperature or ambient temperature. Some late-model vehicles can take the ambient air temperature into account to avoid false activation of the TPMS light.
Find the Leak, Prevent the Leak
Often the sensor will be hit during removal or installation and the seal between the rim and the sensor's valve stem will be disturbed. This can cause a slow leak. In addition, the service parts of the sensor have a limited lifespan because the heat from the brakes and other environmental contaminants can cause the soft components to degrade and the metal components to corrode.
With that said, never reuse nuts, grommets or valve stems. Aluminum TPMS valve stems and nuts are anodized to prevent galvanic corrosion and material deterioration. The nut has a bonded lubricant to help provide the proper torque required for seating a new grommet. If a nut is reused, the anodized surface may be scratched away and corrosion may occur between the sensor, wheel, and stem.
Snap-in valve stems and grommets conform to the mating surface of the rim. The instant the nut is torqued or a valve stem is pulled through the rim, it starts to take on the shape of the surfaces against which it is sealing. This memory cannot be erased, so if the seal is reused, it could cause a slow leak.
Alignment & Inflation
If the rear tire pressures are too low or high, they can change the caster setting. This could cause poor steering feel and hurt straight-line stability. If the front tires don't have the same pressures, they could cause the vehicle to pull in the direction of the lowest tire.