Technology has an ironic way of solving one set of problems while creating another. When bias ply tires and leaf spring suspensions dominated the trucking industry decades ago, drivers expected trucks to ride like trucks. I can still remember an entire summer of balancing tires for a school bus fleet because we eliminated a vibration for one driver. Word traveled fast around the garage and within a week of iproving the ride, we had a steady stream of drivers with similar problems that we were happy to solve.
Ride complaints have definitely changed over the years for a variety of reasons. Tubeless radial tires, air-ride suspensions and aluminum wheels are just some of the components that have improved the experience in the driver’s seat. As a result, the expectations for a smooth ride behind the wheel have steadily risen so even the slightest vibration is no longer acceptable.
When I was balancing bus tires as a technician, we used the traditional method of installing wheel weights to offset any imbalance. Truth be told, I was particularly good at on-vehicle strobe balancing, which balanced the entire rotating assembly. I could set a cup of water on the fender of the truck and literally make it as smooth as glass. But it could be incredibly time-consuming and was rendered ineffective the moment a wheel or rim was removed from the vehicle.
Computerized balancers eliminated the removal issue. One wheel weight is installed on a rim flange to offset the static imbalance, or hop, while another is installed on the opposite rim flange to offset the dynamic imbalance, or wobble. The basic technology hasn’t changed much over the years, but the equipment is definitely more sophisticated and more accurate than it was years ago.
The latest entries in the truck tire balancing sweepstakes are internal balancing compounds, which are added to the interior of the tire. The principle here is that centrifugal force will force them to the outside and offset any imbalance. Unlike traditional wheel weight methods that balance the tire and wheel assembly at one particular point in time, internal compounds are thought to continuously balance the tire throughout its entire lifespan.
While each method has pros and cons, there is one point that is overlooked and ignored too often. If the tire is not concentrically seated on the rim, all of the balance and suspension technology on the planet cannot offset the constant variation in the rotating assembly. This is particularly important on steer axle tires, since even the slightest amount of non-concentricity can result in a ride disturbance and/or irregular treadwear pattern.
Checking for concentric bead seating is easy. All you have to do is measure the distance between the edge of the rim and a molded rib on the lower sidewall of the tire. While the industry will allow up to a 2/32-in. variation in the distance, any variation will have a negative effect on the ride and treadwear.
In most cases, the solution is simple. After deflating the tire and unseating the beads, the tire and rim should be lubricated with rubber lubricant and the beads should be reseated with the tire laying flat. Lack of lubricant, improper lubricant or seating the beads with the tire standing vertical are often the most common causes of non-concentrically seated beads. When properly mounted, installed and inflated, most truck tires should not require any additional balance. And while there are always exceptions, finding balance is not nearly as difficult as it used to be.
