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Weighing Options: Mechanical Balancing or Balancing Compounds?

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There is no easy answer to this age-old question, because each choice has merit. Fleets on both sides of the argument are sold on their choice and most are not about to change their minds anytime soon.

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Think of it in the same way people think about cars. Some will only “buy American,” while others will only choose an import brand. Both sides are convinced their preference is superior, and their reasons are their own, but they are mostly based on past performance and value for the money.

For fleets of all sizes and types, the tire/wheel balance method of choice also comes down to past experience and cost. Regardless of the means, one fact remains: In order to deliver optimum performance, medium and heavy truck tires need to be properly balanced.

While the traditional method of balancing tires - mechanical balancing, complete with wheel weights - remains a tried-and-true method, some fleets have turned to balancing compounds, granules or beads that are injected into the tire cavity.For years, fleets – if they balanced tire/wheel assemblies at all – relied on mechanical balancing, complete with wheel weights. In more recent years, some fleets have turned to what they see as a simpler solution: balancing compounds, granules or beads that are injected into the tire cavity or come in a bag that’s added when tires are changed. When the tire is rotating under use, the materials act to “balance” the tire/wheel assembly. Ardent users are more than satisfied with the results.

The important thing to remember is that each method works. As a tire dealer, you have a choice to present to the fleet customer. From our vantage point, you would do well to research the customer’s wants and base your advice on what best meets those needs.

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A Look at Balancing Compounds
Those in the business of manufacturing balancing compounds say the tire/wheel is continuously balanced. Whether beads or granulated, the compounds are said to last the life of the tire, and maintain constant balance because they readjust their position inside the tire as often as required and are not subject to the effects of road hazards and obstructions. Plus, these products are less expensive for a dealer vs. the investment in balancing equipment, tools and weights.

Another advantage, said a user, is that these compounds effectively dampen steer axle tire/wheel vibration, an up-down motion that impacts tires, axles, wheel fasteners and vehicle components.

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March of the Machines
Let’s listen to Hunter for a moment. Its newly patented Smart Weight balancing technology is a balancing method that minimizes correction weight usage and maximizes productivity, saving money on both material and labor costs. Unlike traditional balancing, which judges balanced condition based on correction weight values, Smart Weight balancing uses the actual static and coupling forces, directly addressing the source of vibration problems.

What About ‘Slop’?
From Bridgestone Americas comes news we’ve all known for years. Engineers don’t like the term “slop.” They prefer the world “tolerance,” but either way, what we’re talking about is the difference between the expected or nominal measurement and cold, hard reality.

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A steel bar isn’t exactly one-inch in diameter even if that’s what the label on it says. It’s one inch, plus or minus an accepted tolerance. The plus/minus might be just a few thousandths of an inch for an expensive bar or many thousandths of an inch for one whose dimension isn’t hyper-critical.

In one example from Bridgestone, a fleet customer was experiencing steering wheel wobble at about 65 mph. The runout of the steer tires was measured. The left front came in at 0.080 while the right front had only about 0.040 of radial runout. Neither measurement is huge (a typical wheel might have a runout of about 0.025 and a typical tire about 0.050) but what was suspicious was that the measurements were so different from one another. Lateral runout on both tires seemed to be minimal.

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When the tire and wheel assemblies were pulled and put on the balancing machine, the radial runout was again measured. This time both tires were almost identical at about 0.030-0.035, a substantially lower differential.

Hunter Weighs In
An aggressive marketer, Hunter Engineering said mechanical balancing is the best option. As an example, its GSP9600HD computes the true first harmonic assembly high spot, and then automatically positions this high spot to top dead center to be marked by the operator for future reference.

A marked tire/wheel can be properly mounted, taking into account the mounting position of the tire/wheel’s high spot in relation to the others on the truck. In most dual assemblies, high spots are mounted opposite to maximize tire and ride quality.

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Said Hunter, in this way the GSP9600HD automatically measures assembly diameter with every balance. With this information, techs can match dual wheels and drive tires on common axles with similar diameter assemblies to improve tire life and prevent uneven wearing and damage.

What Coats Has to Say
Hennessy Industries agrees that mechanical balance works best, and it has taken it a step further to make balancing tire/wheel assemblies quick and painless.

How about an efficient 12-second cycle time on most truck tire/wheel assemblies? How about simple calibration and automatic hub nut loosening and automatic rim gauge return? Coats said that it can balance the full range of heavy-duty, RV and light truck tires, as well as single-spin dynamic static and RV balancing modes.

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Specifications for its tire/wheel balancer allows for cones to prevent grooves and wear, and no pulleys or belts to adjust, wear, slip or break. Tire diameters can range up to 46 inches with a wheel width of 4-1/2 to 18 inches and wheel diameters of 16 to 26 inches. Maximum tire weight is 350 pounds.

Vibration Complaints
Tire/wheel vibration is a common complaint for many companies and fleet drivers today. Such excess vibration causes wear and tear on the truck, uneven tire wear, additional tire maintenance plus increased fuel costs and even health problems due to the constant stress on the body. In short, tire/wheel vibration can cost companies and drivers thousands of dollars annually.

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But not all vibration problems are directly linked to balance.

One company’s products are designed to reduce the rolling resistance of a tire by properly centering the wheels. This decreases tire vibration, which decreases fuel cost and increases tire life by 50% or more, says True-Balance. Now that’s saying something.

“Our patented wheel centering system is like nothing else on the market. It is not a fluid or bead product that you add to the tires, nor is it a wheel balancer. It is a wheel centering system which centers the wheel on the wheel stud rather than the hub pilot, thereby creating a true center of the tire and wheel,” the company said.

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The theory is that hub pilots center the wheel. But Tru-Balance says not so. The fact is, according to the company, gravity causes the weight of the wheel and tire to rest only on the upper one or two pilot holes, leaving a gap on the remaining holes. This is evident by the rust marks left on older wheels where the hub pilots touched.

This results in a wheel not being on-center, thereby creating an egg-shaped motion when rotated. This uneven motion adds to rolling resistance. Even with proper balancing of a hub piloted “centered” wheel it can still be off-center. The bottom line is you can’t balance an egg.

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According to Tru-Balance, wheel-centering products bypass the hub pilot and actually center the wheel to the wheel studs using the 12, 4 and 8 o’clock positions.

There is much more to write on this subject, including a veritable treatise on balancing compounds vs, mechanical balancing. In the months ahead, we will again tackle the advantages and disadvantages of both.

One thing we should know is that any controversy with these systems will be worked out and it will happen in North America rather than Western Europe or Southeast Asia. Count on it.

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