How to Properly Check Tractor-Trailer Tire Air Pressure?

Properly inflated or acceptable tread-level tires on a semi-tractor and trailer greatly increase fuel efficiency, steering safety, tire wear, and emergency handling, as well as help avoid infractions during a Department of Transportation inspection or worse.

Tools Required

Despite commonly held beliefs, using a rod or stick, commonly called a thumper to hit each tire is not the proper, effective, or accurate way to check tire pressure. The under-inflated tire may not sound different enough from its fully inflated neighbor to be noticed with a thumper, but the few pounds’ difference in air pressure often differentiates between stopping safely in an emergency and causing a traffic fatality.

You need two items to check air pressure properly:

A working pressure gauge, and

A working air hose, if needed.

How to Check Tire Pressure

Before checking tire pressure, know the proper PSI or pounds-per-square-inch pressure setting for each tire. If necessary, have available the pressure card your company provides or read the information provided on the tire, itself.

Use a properly operating tire pressure gauge and evenly press the valve end onto the tire stem of the tire. If the initial hissing sound does not fade, the gauge is not properly positioned. Adjust as necessary.

The increment scale should pop up and hold in position, allowing you to read the current PSI. If the tire has too much air, gently depress the tire stem, allowing some air to escape. Repeat the test until the tire holds the proper amount of air pressure.

If the tire doesn’t currently hold enough air, gently attach and activate a working air hose. If the initial hissing doesn’t disappear, adjust the fit of the air nozzle on the stem. Periodically check air pressure until each tire reaches its proper PSI.

Note: The PSI settings for steer tires are often different than for drive or trailer tires. Do not inflate all eighteen tires to the same pressure level.

Completion

When a tire holds the proper pressure, replace the air stem cap firmly on the tire. Return the air hose to its holder or coiled out of a travel lane. Secure the tire gauge in the tractor for easy use next time.