Since the 1970s, static balance has been at the head of the list among proving-grounds engineers. But, those machines had to take a back seat for decades as the complexities of vehicle suspension multiplied. Dynamic balance – the wave of the future – probably corrected more vehicle flaws than tire/wheel issues.

Today, vehicle component technology is even more complicated. Wheels are heavier, and large tires capable of running at speeds in excess of 186 mph are common.

Now, two tire-balancer manufacturers are presenting new, static-based methodologies to achieve a vibration-free ride. It’s a little old-school flavor to tackle modern problems.

Built into the newest balancers is the kind of computer brainwork that decides correction weight by evaluating absolute, pure static force, along with forces that cause dynamic balance conditions. The new balancing systems are also able to track down residual imbalance.

Separate Forces

The news from Hunter Engineering Co., which unveiled its Smartweight technology first, is almost too simple to be believed. “What we have discovered changes everything, right down to the way all of us have been balancing tires,” says Hunter product manager Dave Scribner, “and the technology was right under our noses all the time.”

Hunter Smartweight balancers are programmed with limits based on the amount of force needed to induce a noticeable vibration on a given tire/wheel assembly. This force cancellation tracks down residual, static imbalance that older systems would ‘hide’ with weight-rounding, two-plane functions.

Unlike dynamic balancers, which judge balance conditions based on correction weight values, Smartweight evaluates static and couple forces independently. Then, it applies separate limits and computes correction weight based on vibration-force reduction.

Hunter notes that traditional balancers use a fixed tolerance on correction weights, regardless of the weight location chosen. This places equal emphasis on static and couple imbalance.

Here’s the rub. All vehicles are inherently more sensitive to static vibration force than couple force.

With most wheel assemblies, this tolerance is too loose for static imbalance and too tight for couple imbalance, something that can result in excessive residual static force.

Even when the balancer cancels out static and couple forces to zero, correction weight is never zero. Says Hunter: Zero correction weight is merely a function of the weight locations chosen.

The new system works first on getting rid of static imbalance, the up-and-down movement of the tire/wheel assembly, which causes vertical shake or static imbalance.

Next, the new system looks at “wobble” or couple force. This is what we used to call dynamic force. The shaking moment is a totally different engineering unit of measurement than static force. Couple force is actually comprised of two weight radii, and correction weight has a different effect on each force.

Back to Static

“Our industry has come full circle – from basing its technology on static balancing to dynamic balancing and now back to a renewed emphasis on minimizing static imbalance,” says Kevin Keefe, director of marketing at Hennessy Industries. “We are now in a state of what we call a ‘new balancing mode,’ where we reduce static imbalance first, and then, if necessary, work on reducing dynamic imbalance.

“The latter comes into play depending on type of vehicle and type of customer. Like the old timers, we are looking for the sweet spot that will please the owner of the vehicle and cause few, if any, comebacks,” Keefe says.

Important to this aspect of the process is the ability of the balancer to allow itself to be fine tuned. We can now strike a balance between weight savings, productivity and the potential for comebacks. “The news is that now we can adjust this window,” says Keefe.

“Our research shows that static imbalance drives 80% of all vibration-related comebacks. We want dashes in the display windows on our balancers equipped with new technology we call EconoBalance,” he says. “In those windows, we are displaying both static and dynamic imbalance and correction modes while keeping a sharp eye on residual dynamic vibration.”

Why is static the subject of such renewed scrutiny? Just 10 years ago, we all knew that tires, wheels and other axle-end components attacked the suspension with the force of a tack hammer.

But, with today’s beefier vehicles, the disturbance is much more like a sledgehammer. “We’re dealing with more unsprung weight than we were a few years ago,” says Keefe.

Also important to the manufacturers of the new balancers is that the systems are not shortcuts. To the contrary, both systems are “super accurate” in their ability to eliminate static balance. They also maintain a tight audit on couple force when it exceeds limits.

Again, Hunter says: “As these machines and their newly designed balancing programs reach original equipment vehicle makers, it is expected that they will also save money when correction weight is used as a gradient.”

A Precision Balance

Unlike traditional balancing, which judges balance condition based on correction weight values, the newest balancing technology measures static forces, dynamic forces and hidden residual imbalances to address vibration problems. The reward to the consumer is the best-possible balance.

The reward to tire dealers using one of the new tire balancers is 30% to 40% less weight usage, fewer comebacks and increased productivity, thanks to fewer respins and time saved pounding on fewer wheel weights.

Another way to improve balance and cut lead weight use, according to International Marketing Inc., is to stop using lead weights. IMI’s XACTBalance system is the first lead-free, active adhesive wheel weight made for all types and sizes of wheels.

The product adapts automatically to changing tire and driving conditions, with free-moving steel media housed in a flexible thermoplastic shell. As the wheel and tire rotate, according to IMI, the media adjusts, targeting the exact location of the imbalance and correcting it. The result, said the company, “is a more precise and longer-lasting balance.”

It has always been easy to lay the imbalance blame on tire or wheel makers. That will change as balancing technology allows all forces to be measured accurately, including sometimes hard-to-find residual balance forces.

We already know that tire companies and vehicle makers are thrilled about the new balancer technology. It is estimated that 30% of the tire/wheel assemblies balanced with this kind of technology will not require any correction weight, and 70% will require just one weight.

You can almost hear a sigh of relief coming from tiremakers, and it’s about time. This is already a big story, and it’s only going to get bigger.