Maintenance

A Question of Balance

June 2009, TruckingInfo.com - Feature

by Jim Park, Equipment Editor, Equipment Editor - Also by this author

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Do we really need to balance our tires? Predictably, and depending who you ask, the answers are yes. Or no. Improvements in manufacturing processes guarantee a much better tire comes from the factory today than even a decade ago.
But we have to consider which factory.

Name-brand North American tires have better build quality - mostly - than the no-name offshore imports. The adage about getting what you pay for holds true here. A tire selling at half the price of the name-brand merchandise is going to be short on something.

Chris Tolbert, a business segment manager at Michelin, says balancing generally isn't necessary with Michelin tires.

"Balancing is part of tire verification checks we do within the manufacturing process," he says. "Given that, we generally don't recommend any balancing at installation."

Guy Walenga, director of engineering for commercial products and technologies at newly formed Bridgestone Bandag Tire Solutions, agrees for the most part, but says when considering balance, you need to take the entire wheel/tire/hub and possibly brake drum assembly into consideration.

"New tires today are so close to tolerance compared to what we saw 20 years ago, it's like two different tires. I'd say that if mounting procedures are followed and care is taken to seat the tire properly, tire balance shouldn't be an issue," he says. "But when you look at the entire mass that's spinning around on the axle, we could often make a case for balancing."

Peggy Fisher, president of TireStamp and a highly regarded tire expert, says a properly balanced tire will wear more evenly over its life, so there are advantages to taking the extra step, if only because it's cheap insurance.

"Unless you have a flat spot from a skid, or something mechanical goes bad that causes the tire to run irregularly, in most cases, if it's left to its own devices, and if it was mounted correctly and balanced, it should run OK," she notes. "Unless bad things happen to it."

Fisher says many fleets don't bother at all with balancing, but if they do, they'll probably do only the steer tires. "That's mostly to avert driver complaints about vibration," she says. "Some will balance their drives, but not many; very few fleets bother balancing trailer tires."

Mount Up And Ride

Many balancing issues arise when new tires are mounted. If they're not centered exactly on the rim, you'll get a high spot in the tire's rotation, which will be felt by the driver as a vibration - much the same feeling as an unbalanced tire.

Non-concentric mounting produces a wheel/tire assembly that is basically out of round. Fortunately, it's easy to check (see sidebar). "If it's not straight, dismount the tire and try again," Walenga advises.

Some new tires have colored balancing dots on the sidewall of the tire. These aid in aligning the light spots on a tire with the heavier sections of the rim, i.e., the valve stem. Follow manufacturers' guidelines to align the dots properly.

Even with today's tight tolerances, hub-piloted wheels can be mounted slightly off center, and it doesn't take much to start a vibration. Follow procedures recommended by your hub supplier. There are tools available to help with hub-pilot mounting, such as the Tru-Balance truck wheel centering system, and others. "Budd-style" wheel have pilots on the studs, and the Dayton "wagon-wheels;" both will self-adjust as they're torqued down, as long as proper torqueing procedures are followed.

Having said all that, before you mount the wheel on the hub, it wouldn't hurt to visually inspect it and the brake drum for potential sources of vibration. Sometimes brake drums have weights welded to them at the factory. These have been known to come off, upsetting the balance of the drum. As well, drums often have holes drilled into the outer flange for the same reason. These may fill up with dirt or debris, which could also compromise balance.

If that doesn't get it, try rotating the tire 180 degrees with respect to the wheel, remount and check concentricity again. If you still have no luck, try another tire or another wheel.

Beads, Bags, And Bangles

So, to this issue of actually balancing the wheel/tire assembly. If we assume the tire is properly manufactured and mounted, a dynamic balancing machine can fine-tune the process, verifying both dynamic and static wheel balance. With the prescribed amount of weight properly attached to the inner and outer sides of the rim, you're good to go.

Fisher says balancing drive tires isn't a common practice, but there could be incremental improvements in tread life and wear characteristics derived from balancing.

"If a fleet is really interested in getting every last 32nd of an inch out of a tire, they'll balance," she says.

Unfortunately, tires can wear irregularly for a number of reasons. Fixed lead weight balancing will not help a tire that is losing rubber from different places around the tire. Here, a balancing compound placed into the tire or mounted to the hub in a ring can minimize vibration caused by the irregular weight of the tire around its circumference, but it won't stop or improve the irregular wear.

"That's probably got another cause altogether," Fisher notes.

Bridgestone Bandag's Walenga suggests a balancing compound can be useful in troubleshooting a ride or wear problem.

"If you've got a problem, you could isolate the tire by using a balancing compound. Once you're reasonably sure the vibration source isn't the tire, you can begin looking elsewhere," he suggests.

Placing some material inside the tire, mounting a lead weight to a rim, or using a balancing ring all achieve the same objective equally well, in most cases, Fisher says. But there are other factors to consider.

"Powders, for example, had a bad reputation at one time for clumping up inside the tire if exposed to moisture. We all know how dry shop air can be, particularly the variety that available at a truckstop," she warns. "Those chunks could tear up the inside of a tire casing pretty badly."

Many products available today claim to be moisture resistant or non-clumping. So it must have been an issue at one time, even if that problem is behind them now.

Powders and liquid are not reusable, Fisher says, and the liquids could be hazardous. They may not contain enough rust inhibitor, either, which could cause corrosion problems with aluminum wheels or rusting inside steel wheels.

Be aware, too, that some powders can clog valve stems. Or, if the powder clings to the lubricant on the wheel flange when mounting, it could prevent a perfect seal.

Some powders come in bags now. You toss the bag into the tire, and it self-destructs with in a few miles of installation.

Balancing rings are yet another alternative, but these too, come with a caveat or two. Mounting at the lug nuts can cause problems if the material isn't properly hardened. Fisher warns that the mounting surface could deform under torque.

"It compresses, and after repeated use, could become burred. That can eventually lead to loose wheels," she says. "Take care, too, that the balance ring does not interfere with the brake drum or wheel."

As Michelin's Tolbert suggests, read the instructions first.

"We strongly caution our customers to read the product warnings and data sheets that come with all the product out there," Tolbert says. "You want to stay away from anything that can damage or deteriorate rubber, such as petroleum-based products, or alcohol, silicon, or high-pH materials."

None of the experts we spoke to in compiling this article had any particular feelings regarding balancing wide-base single tires. They all said the issues and solutions were about the same, although TireStamp's Peggy Fisher did say you might experience more lateral run-out only because the tire is that much wider.

"They're heavier and more cumbersome to maneuver than a sin

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