Understanding Tire Pressure

Recommended tire pressure

Why tire pressure is important for heavy-duty vehicles

Before a truck hits the road, drivers perform maintenance checks to ensure that every piece of the vehicle is operating as it should. While testing components like the lights, batteries and brakes is essential, it’s important to not overlook the tires when doing a pre-trip inspection. Properly pressurized tires help support the load, optimize fuel efficiency, and keep the equipment and driver safe. By checking tire pressure before a truck leaves the yard, fleets can minimize the risk of damage and potentially avoid emergency tire repair.

Tire pressure FAQs

Because tires are such an important vehicle component, it’s imperative that they’re well maintained. Understanding the aspects that change tire pressure, and how they ultimately affect performance, can make it easier to adjust your maintenance strategy to better fit your fleet’s needs. Here are the answers to some commonly asked questions:

How do you check tire pressure?

While some vehicles may have tire pressure monitoring systems to alert drivers of any problems, it’s still important to perform manual checks. Monitoring systems are typically regulated to signal when the pressure drops below a set pounds per square inch (PSI), but that setting may be for a PSI reading too low to support the load. To check the tire pressure, simply:

  • Remove the valve caps
  • Place a tire pressure gauge on the valve stem (be sure to firmly press down until you can no longer hear air escaping)
  • Read the gauge and compare to the target PSI

Are pressure gauges accurate for commercial tires?

­Yes, as long as the gauge is in good condition. Your truck tire gauge should be calibrated and kept in a protective sleeve when not in use. Dirty, dropped or otherwise damaged gauges can give inaccurate readings. It’s also a good idea to compare the tool to a master gauge to be sure it’s calibrated correctly — most fleet maintenance shops will have one, or you may be able to use one at a tire store.

When should you check tire pressure?

Accurate readings are dependent upon a consistent environment. To ensure PSI is being measured correctly, you should always check the tires when they’re “cold” (i.e. haven’t been driven on recently or been exposed to direct sunlight or hot pavement). And because commercial vehicles are often unused for an extended period of time and cover many miles in a single shift, it’s a good idea to test the pressure before every trip.

How does temperature affect pressure?

There’s a common idea that tires should have more air in the winter and less in the summer. This belief is based on the fact that air will expand in the heat and contract in the cold. And while it is true that tire pressure will fluctuate with the temperature (about 1 PSI for every 10 degree Fahrenheit change), the winter/summer rule isn’t entirely accurate because tires are designed to withstand some pressure variation. So, as long as you measure the pressure while the tires are cold and only inflate them to the PSI they need, you shouldn’t have to worry about adjusting for the temperature.

Should you use the manufacturer’s recommended tire pressure?

Yes, you should. There may be times when heavier loads necessitate a slightly higher PSI, but the recommended tire pressure is ideal for most situations. If you’re operating with mated dual tires, it’s important to keep them inflated at the same level — otherwise, you may cause damage to both. Keep in mind that the tires on the tractor and trailer may have different needs, so you should always check that you’re inflating them to the manufacturer’s recommendation.

What happens if commercial tires are underinflated?

Underinflating can be detrimental to performance and cause tire failure. As a vehicle moves, a section of each tire is always in contact with the road. With each rotation, friction (and heat) occurs. If the pressure is too low, more of the tire’s surface touches the road — thus creating more friction. This can cause overheating, tread separation and blowouts.

Can tires be overinflated?

Yes, and it should be avoided. Exceeding the manufacturer’s maximum tire pressure can lead to loss of traction and premature wear, as well as causing a bumpier ride. Tires need to have some flexibility in order to operate correctly. When they’re overinflated, the structure of the tire alters slightly and affects performance.

How does tire pressure affect performance/gas mileage?

If truck tires aren’t properly inflated, the vehicle has to work harder to create motion because there’s more friction (also known as tire rolling resistance). If the engine is putting more work into creating movement, the fuel economy is negatively impacted. According to fueleconomy.gov, gas mileage can be improved by up to 0.6 percent on average simply by keeping tires properly inflated.

Monitoring your commercial tires 

Do you know how many tires you replaced or repaired in the last year? Were any of those repairs due to improper tire pressure? If you’re not sure, you may be missing cost-saving opportunities. Keeping track of unscheduled events and performing regular preventive maintenance checks and pre-trip inspections helps your fleet operate efficiently. Find ways to reduce downtime and save money on repairs with the robust data and analytics FleetNet America® can provide. For more information, call 1-855-836-3912.