Balancing For Bucks
So what if a line haul driver can’t feel the vibration? Taking a pass on balancing
truck tires is a big mistake for fleets, for drivers and, ultimately, for dealers.
Following the flow of technology is going to help your fleet customers. That’s the trend. If you save them money, they love you for it. Foul up and you’ll hear about it. If you don’t already know it, fleet customers also want you to suggest new ways for them to save money.
Here’s a good one – tell them why they need to properly balance their drive and trailer tires. Fleets do a good job with the steer axle tires, if only because their drivers can feel any imbalance in the steering wheel, but most haven’t adopted the practice of balancing the remaining 16 tires.
The assumption is that a heavily loaded truck will dampen any vibration. That’s just not true and fleet owners who aren’t balancing all 18 tires are sacrificing more than just ride quality.
Here’s what you say to these people. "Proper balancing will cut down on the chance of an irregular wear pattern setting up, which will add to the life of your tires, and deliver the kind of takeoff mileage that results in good lifecycle costs. Plus, that will provide a more retreadable casing. That means two good retreads per tire." That, as they say, is real money.
Did we also mention that by properly balancing tire/wheel assemblies, they’d eliminate vibrations that cause added wear and tear on chassis parts?
Runout Still There
While it’s true that tiremakers are providing safer, more reliable, longer-lasting medium truck tires than ever before, radial runout remains a sore point. So the job of managing and understanding the problems caused by this condition falls to you.
First, you need to understand that a pair of zeroes on a balancer (inner and outer planes) does not mean you’ve properly balanced the tire/wheel assembly. Your job isn’t over until you center the assembly on the vehicle the same way it was centered on the balancer.
Nor does it mean you’ve gotten rid of a built-in vibration problem created by a tire or wheel that isn’t perfectly round. There is still work to do.
As Bobby Knight says, basketball isn’t about making great plays, it’s about eliminating little mistakes. Make sure you’ve mounted the tire/wheel assembly on the balancer properly. A truck tire/wheel assembly that is 43-plus inches in diameter and weighs about 250 pounds will have more than several ounces of imbalance when mounted off center by as little as 0.005 of an inch.
According to Hennessy/Coats, mounting errors (balancer and vehicle) cause 60% of all vibration-related comebacks. Further, 80% of mounting errors are static related.
Looking deeper at the reasons for comebacks is equally revealing. Some 10% are for a balancer that is out of calibration, says Hennessy/Coats, 7% from improper weight application, 6% for eccentricity (or radial runout), 4% from improper lug nut torquing, and 3% from using used wheel weights and clips.
Put It Back the Way You Found It
The first secret to balancing medium truck tires is to make certain you are mounting the tire/wheel assembly on the vehicle exactly the same way you mounted it on the balancer. Replication is vital, and more so with truck tires than with their smaller cousins.
Note, however, that balancers are different by design and construction. For that reason, talk with your supplier for specifics about proper mounting procedures. You will also find that different suppliers have somewhat differing philosophies about balancing, and use different words to describe the same thing.
The good news is almost everyone is in agreement about most balancing issues. At the top of the list is taking care of fundamentals.
For example, you can help minimize radial runout by mounting the high spot of the tire (indicated by a paint dot on the sidewall) to the low spot on the wheel (indicated by a dimple). If you can’t find the dimple, use the valve stem opening as your reference point.
Next, don’t mount the tire dry, use proper lubrication. The bead must seat properly on the rim. Also important, don’t limit the use of lubricant to the tire alone. If you see a hump on the wheel that looks like a problem, put lubricant on it to facilitate a better mounting job. But don’t overlubricate or you’ll have wheels spinning loosely and tearing up beads.
Here’s another tip. When mounting medium truck tires, more errors occur with demountable and stud pilot wheels than hub pilot wheels. That’s because the inner cap nuts may not have bottomed out all the way, and are improperly seated. Look for dirty threads and make sure that torque specifications have been carefully followed. Demountable wheel clamps can also contribute to a centering and/or vibration imbalance problem.
A tire/wheel mounted in this manner will wobble. That sets up a scuffing motion which causes an irregular wear pattern and creates a vibration in the vehicle. Worse, the driver, isolated in the cab, will not feel any of this. You’ll have to eyeball the tire and read the signs of irregular wear to diagnose this problem.
At Hunter Engineering, Mitch Weller, heavy duty product manager, says, "I’ve seen 20 ounces of imbalance that can’t be felt in the cab. The concern is that the frequency of the vibration will not only set up an irregular wear pattern on the tire, shortening its life, it also cuts down the carefully engineered life of chassis components."
Part of the problem, according to Weller, is that many fleets buy pre-mounted, pre-balanced tires, which they mount on trucks with huge hubs and brake drums – without independently checking the balance. The twist here is that the balancing machine assumes that the tire/wheel assembly will be mounted and centered the same way on the truck.
"Keep in mind that while the tire/wheel assembly might be perfectly balanced, it is being mounted to another large, rotating assembly. If the whole thing is out just 10 ounces you are looking at a problem in the making."
Making the problem of diagnosing imbalance even tougher is that certain conditions can mimic static imbalance. Flat spotting can be the culprit, as can a manufacturing defect in the tire or in the wheel or even a build up of dirt around the wheel.
According to Kevin Keefe, group marketing manager at Hennessy/Coats, the average comeback costs you in time, labor, materials and the margin on new work while the balancer is busy correcting a mistake.
In other words, getting rid of mistakes before they occur will keep your truck tire customers happy and you in their good graces.
Added Additive Options
There is one more area to discuss: The growing use of dry balancing compounds. This material can be introduced through the valve stem or it comes in bags that are put in the tire before it is mounted.
Many view these products as adjuncts to conventional balancing methods, rather than as a replacement. Dry balancing compounds comply with the laws of physics: every force creates an equal and opposite force.
International Marketing Inc. pioneered dry balancing agents with its Equal product, a dry polymer. Once in the tire, the product is forced across the tread width and around the circumference of the tire, says IMI President and CEO Bob Fogal Jr., and it repositions itself with load and speed changes to eliminate vibrations.
"Equal and its ability to replace the need for lead weight balancing is supported by testing from Penn State, Ohio State, other independent studies, and one of the top tire companies," he says. "Our product is 20% to 30% better at reducing vibration than conventional lead weight balancing and we have the empirical and scientific evidence to back it up.
"In our view, a dynamic spin balancing is not valid unless it is performed with the tire/wheel assembly mounted on the vehicle," says Fogal Jr. "Traditional balancing cannot offset the effects caused by the tire/wheel force variation. Any simple change to the tire and it’s out of balance again."
Ian Savidge with M&R Tire Products Inc., says that as a tire rotates it is compressed by the weight of the vehicle as it comes out of the contact patch. M&R’s Magnum dry balancing compound "pulls away from the heavy spot, moving in the opposite direction, thereby offsetting the effects of the heavy spot. As the tire rotates, centrifugal force distributes the compound evenly around the interior of the tire."
Magnum also comes in a bag, and is especially effective in slower rotating medium duty truck tires because it has plenty of time to get where it is going. "In this way, the dry compound material allows the tire to be continuously balanced," says M&R.
If you’re looking for a bottom line to this story it’s all tied to your ability to be accurate, attentive and consistent. Fleets use the term "preventive maintenance," and you’re part of the equation.
Tell them what they need to know about balancing truck tires and how this procedure can help them balance their books.