As we approach the 30th anniversary of the greatest trucking movie of all time, it's important to note the historical significance of “Smokey and the Bandit.” The year was 1977 and the tires were bias tube-type on multi-piece rims. Since I began my career in the tire industry as a technician in 1982, I'm intimately familiar with that era and how much the landscape has changed since then.
One of the underlying principles for servicing multi-piece assemblies was the installation of inner tubes in new tires. Very few drivers or companies ever questioned the need for a new tube because everyone understood the consequences of wrinkles and creases. While the number of tube-type tires on multi-piece rims currently in use continues to decline, the importance of the inner tube will never change.
Tubeless radial truck tires that dominate the industry today are also dependent on an air retention device called a valve stem. Like the inner tube, if the valve stem fails, the tire will eventually become flat. While some fleets recognize the importance of replacing the valve stem when a new tire or retread is installed, others have determined that the extra cost cannot be justified, so they just roll the dice.
Truth be told, the valve stem itself doesn't wear out as fast as the rubber grommet or silicone O-ring. As these components deteriorate with age and dry out or harden, the chances for a leak will increase. But the hex nut that holds the valve stem in place and compresses the sealing mechanism (grommet or O-ring) also loses a certain degree of performance capabilities each time it is re-tightened. Since there's no way to easily determine if the valve stem components are worn out, the safest move is to replace the entire assembly.
But before you establish a “new tires and retreads get new valve stems” program, make sure you are getting high quality valve stems. To the outside observer, they all look the same, but there have been instances where the brass is so porous that air actually migrates through the walls of the valve stem. The best move is to look for a TR number and manufacturer identification stamp on the end of the stem. Valve stems with no markings may not meet the performance requirements of today's tubeless radial truck tires.
Like every other component on the vehicle, if the valve stem is not properly installed the consequences can be severe. Believe it or not, each type of valve stem has an installation torque and failure to follow the specifications can lead to a number of problems.
Steel wheels have a fairly large margin of error, so the most common problem associated with an improperly installed valve stem is a flat tire. Valve stem installation torque on aluminum wheels, however, is far more important because over-torquing the hex nut can compress the O-ring to a point where the valve stem base contacts the rim. When this happens, corrosion is typically the end result. If it's severe enough, the wheel will have to be removed from service. There are few things more aggravating than a $300 wheel in the scrap pile simply because the valve stem was improperly installed.
As ridiculous as it may seem, having an effective and universal valve stem policy can prevent nuisance flats and protect aluminum wheels. By working with your retreaders and service providers, you should be able to develop a program that makes sense from both an economical and operational standpoint.