"Once the compound is in the tire, the dynamic balancing machine will try to compensate for the weight of that material, which is always moving inside the tire. You'll never get a proper balance on a machine with something in the tire," he cautions.
Powders, Liquids & Rings
These tools have some advantages over traditional tire weights, says Peggy Fisher, tire guru and president of TireStamp.
"One of the advantages to these alternate forms of balancing is that they will adapt to the tire as it changes shape with age," she says. "As rubber wears off the tire, especially if you have irregular wear from some other source, the balancing compounds will compensate for the missing rubber by moving around within the tire. Weights can't do that."
She also notes that throwing a bag of balancing compound into the tire is less labor intensive than hoisting the tire and wheel onto a balancing machine, but is one a demonstrably better way of balancing a tire? "Both achieve balance well," she says, "but there are other things to consider."
With powder or liquids, you can't always use them over and over again. Some liquids require special disposal. Some are notorious for rusting steel wheels. Some powders can clog valve stems, and if the powder comes in contact with the bead seat area, it can prevent the tire from seating properly.
"Also," she warns, "some powdered materials can clump up and turn into basically rocks if they come into contact with moisture -- which is pretty common in most truckstop tire fill systems. Having those rocks flying around inside the tire can wreck liner."
Fisher says she has also seen good results with the external balancing rings, but she cautions that if the mounting surface of the ring is not hardened steel, they can cause problems with wheel fastener torqueing.
"Softer metals can compress under torque, which can cause fasteners to loosen over time," she cautions. "Check with the manufacturer to ensure they are using hardened material, or at the very least, make a habit of checking your wheel fastener torque more frequently."
Balancing the System
So far, we have only discussed the tire and wheel. On the truck in real life, you have the hub and brake drum to contend with, each of which could be out of balance. Brake drums, for example, often have weights welded to the drum or cores drilled out to achieve a static balance. But if the weights fly off or the cores fill with dirt, balance comes into question, Walenga says.
"The rings and balancing compounds are an attempt to continuously address balance as the tire rolls, and they'll work in this situation. But a properly balanced tire and wheel assembly bolted onto a properly balanced hub and drum is just as good," he says."
Balancing is usually unnecessary with today's premium tire because of the consistency in manufacturing, but Walenga notes that it's an easy way to tweak or optimize the ride.
"I'd spend my time and money optimizing steer tires because that's where a driver is most likely to feel and see a problem," he says.
And Fisher believes that balancing is cheap insurance against premature tire wear. "In most cases," she says, "if a tire is mounted correctly and balanced it should run okay unless bad things happen to it."