December 2013, TruckingInfo.com - WebXclusive
(Photo by Jim Park)
While making a delivery of liquid oxygen, several years ago, to a manufacturing plant undergoing renovation, I had to drive off the paved portion of the road and into some deep mud. Once I had filled the customer's storage tank, I backed out of the muck and headed out to the highway. I had accelerated to about 35 mph when the front end of the truck began shaking wildly – so much so that I was unable to hold the steering wheel.
I slowed and stopped the truck, and then got out to inspect the truck for damage, thinking I had hit something and badly damaged a front wheel. Everything looked just fine on a cursory inspection. A closer look, however, revealed a clump of mud weighing about 5 pounds had lodged itself between the wheel and the brake drum. Those 5 pounds of mud put my right front wheel so badly out of balance that it nearly shook the truck right out from under me.
While that was a dramatic illustration of imbalance, I see similar examples regularly while driving on the highway in my car. I watch trucks while I'm driving, and it's not uncommon to see trailer wheels bouncing wildly down the road. Between the out of balance condition and the centrifugal force acting upon the heavy spot on the wheel, I often see an inch or more of upward movement in the wheel. There's less fore and aft movement because the axle is restrained -- for the time being anyway -- by the bushings.
The driver likely wouldn't notice the vibration with air-ride everything nowadays. But make no mistake, that out-of-balance condition is destroying the tires as well as the suspension bushings, the shocks, and more, as well as impinging on fuel economy.
Nobody balances trailer wheels, but oddly, they are the wheels on a truck most likely in need of balancing. Trailers are the pre-graveyard for tires. They will have been shuffled from a steer position to a drive position, retreaded sometimes, reinstalled at a drive position, and when they are all scabby and worn, they are moved back to a trailer position for a final few months of life until the tread has worn to the last few 32nds of an inch.
Tires consigned to trailer positions suffer all manners of indignity -- gauged, flat-spotted, cupped, run flat, etc. I can't help thinking that with a few ounces of balancing material those tires might easily run tens of thousands more miles before final removal.
Balanced for Life
You're thinking, "There's no way I'm going to pay to balance a half-worn tire at a trailer position."
But when you use a balancing compound instead of a fixed weight crimped to the wheel, the material remains fluid inside the tire, maintaining balance of the tire and wheel assembly regardless how much rubber has disappeared from the tread face or where it came from. According to Bob Fogal Jr., president and CEO of International Marketing Inc. (IMI), products such as Equal can stay in the tire its entire life and keep working for the life of the tire.
"Equal moves freely inside the tire and seeks low spots in the tread and balances the weight of the missing rubber," he says. "The tire remains perfectly balanced due to the distribution of the compound in the tire as it rotates."
The compound can stay in the tire, through dismounting and remounting, and be reinstalled at any wheel position. The balancing material will continue to do its job, indifferent to where it is mounted.
"I think fleets have grown accustomed to the idea that there's little point to balancing a partially worn tire at its second or third wheel position," Fogal says. "It's a cost that won't be recovered because the tire will continue to wear once the patterns have been established.
"With an internal balancing compound, the material adjusts to the tire condition. Even if some external condition such as alignment or worn shocks has caused the tire wear, the balancing material will compensate for the missing rubber and maintain proper tire and wheel balance."
Unlike fixed weights that have to be removed, then reinstalled when the wheel is rebalanced, balancing powders can stay in the tire, and they will go to work in the first mile of rotation.
The same thinking applies to balancing rings such as Centramatic. The dynamic balancing media contained in the ring adjusts to the balance condition of the tire, regardless of the tire condition or wheel position -- all other factors being equal, such as proper mounting and good mechanical condition.
"Balancing isn't something a fleet will do every time a tire is changed or a flat is repaired," says Robert Coolidge, president of Centramatic. "Once you have invested in a set of balancing rings, they can remain at a wheel position, balancing any tire/wheel assembly that is mounted there."
If you look at balancing from a life-cycle point of view, the value of extending tread life speaks for itself, Coolidge says.