If you ask 50 tire experts to name the most important part of a tubeless radial truck tire assembly, you will probably get a number of different answers. Some will point to different aspects of design or materials in the single-piece rim because that eliminated side and lock rings thereby saving the lives of technicians who serviced the assemblies. Others might focus on the 15-deg. bead taper of the tire or advances related to innerliner technology that resulted in the dominance of tubeless tires in the market.
In my opinion, the most important component in a tubeless radial truck tire assembly is the Rodney Dangerfield of the industry: the valve stem. All of the engineering that has gone into rim design, construction and coatings is pointless without a valve stem. Likewise, technological advances in tubeless radial truck tire construction have exponentially improved the performance, retreadability and lifespan, but the whole package is still dependent on a $5 part that most people ignore. That’s no respect in my book.
The first hurdle to overcome is recognizing that the valve stem should be replaced with every new tire or retread, even if it doesn’t leak. No one can predict the lifespan of a rubber grommet or O-ring, but everyone should agree that eventually they will succumb to the demands of a truck’s service and fail. If you’re lucky, someone will catch the slow leak during a pressure check. If you’re not, the gradual loss of air pressure will start with irregular treadwear and end with a roadside blowout. In other words, spending a few dollars for a new valve stem is well worth the investment.
Next, you have to make sure you are getting what you paid for. Valve stems are no different than other parts that come in a plain white box. The quality of the brass or chrome plating will depend on the manufacturer. Some service providers will go the cheap route and source a no-name valve stem to make a few extra bucks while others recognize the importance of an established brand. The known valve stem may cost an extra dollar or two, but the consequences of substandard metal that may accompany the plain white box are the same as those of a failing grommet or O-ring.
Without a doubt, the most difficult thing to control is the person installing the valve stem. It starts with a thorough inspection of the valve hole in the rim, especially after steel wheel rim reconditioning. Excessive paint around the edges of the valve hole will present a problem even if a high-quality valve stem is installed. On aluminum wheels, the surface where the O-ring contacts the rim around the valve stem hole must be clean. Corrosion on any type of rim around the valve stem hole is going to result in a leak, so the technician installing the valve stem must take the time to clean and inspect the area.
Finally, like every nut, bolt and fastener on the planet, the correct valve stem torque is necessary. On most steel rims, it is important but not critical because there is enough grommet material to prevent the brass from contacting the rim. Aluminum rims are a completely different story because the O-ring creates a small margin of error. If the valve stem is under-torqued, it will probably leak. If it is over-torqued, the base of the stem contacts the rim surface and the resulting corrosion destroys the wheel.
A great philosopher once said, “Life is really simple, but we insist on making it complicated.”
While I’m positive that Confucius was not talking about valve stems, I think it still says a lot about the complexity of such a simple component.
