Tire PM

Tires do not live by tread alone, but by other basic preventive maintenance practices that can extend their lives, minimize downtime and save money.

Tires rank second to fuel in operating expenses for an owner-operator. Give tires the proper care and feeding, and you can save hundreds of dollars a year.

Tire maintenance isn’t complex. It involves regular inspections, good practices and good records, as well as learning to interpret those records and your operational experiences.

“Two of the best things you can do for your tires is to keep them at recommended pressure and keep them clean,” advises Doug Jones, Michelin’s customer engineering support manager.

Washing both sidewalls helps prevent cracking, Jones says. “Tires get old from exposure to ozone and from antifreeze and oil products on the road,” he cautions. Solvents and calcium chloride used to treat icy roads also degrade tires.

Maintaining proper pressure is a much bigger issue in prolonging tire life. Mike Guenette, a driver for Dagen Trucking in Albany, N.Y., says he used to check pressures by thumping tires until he learned that it was unreliable. “I carry a gauge now,” he says.

Checking tire pressure with a gauge regularly – weekly is a good frequency – catches serious problems as well as leaks that occur normally over time. Knowing your load weights and calculating inflation pressures from a load chart requires time and attention to detail, but it pays off. When run as little as 20 percent under recommended pressure, tires can lose 16 percent of their life span and 12 percent fuel mileage. Load charts are available from your tire manufacturer.

If you run empty a lot, as some tanker operations do, for example, you may want to adjust pressure before and after deadhead. Remember, too, that traveling at higher speeds generally justifies a higher inflation pressure. Also, check pressures more frequently in winter. During cold months, tires lose 2 psi for every 10-degree drop. A digital tire pressure gauge, available at parts stores and major truck stops, is the most accurate – an important consideration, especially when checking tires on the same wheel end. Small plastic gauges run about $15, while metal gauges with flexible necks may cost twice as much. The flexible neck makes it easy to check inside tires.

Curtis Decker, manager of field engineering for Continental Tire, says tires on the same wheel end should be within 2 psi. “Ten pounds per square inch difference between duals results in a 4 percent increase in load weight on the tire with the higher pressure. This translates into 30 to 45 percent more wear,” Decker notes.

Tires across an axle ought to be as alike as possible, meaning their tread depth, style and inflation should be matched. It does less good to have tires of equal pressure if their tread depth throws weight to one tire because it sits higher on the pavement. If you have to settle for a mismatched tire while on the road, replace it as soon as possible.

Robert Coolidge at Centramatic, maker of tire and wheel balancing systems, notes that when tires deflect off the road at high speeds, emitting the familiar wha-wha-wha sound, they wear irregularly. “The point is to keep the tire on the pavement all the time,” Coolidge says. “Out-of-balance tires cause the buildup of localized heat and the tire warp.” The Centramatic system uses a hub-mounted ring and a balancing fluid inside the tire to maintain balance.

There are also several systems that keep tires automatically inflated. These include products from Roadranger, ArvinMeritor, Airgo Systems, Cycloid Co., Innovative Transportation Products and CM Automotive Systems. The systems can be costly, though the makers point out sizable potential savings from extending tire life and avoiding repairs and downtime.


SIGNS OF WEAR

Operation with improper inflation, as well as certain other problems, will eventually show up as irregular wear. This is best detected by feeling for feathering, cupping or other irregularities. Feathering is characterized by one sharp edge and one smooth edge on one groove. Cupping can be found by feeling the difference in height between a leading and a following edge of a lug or groove. “You can feel irregularities that are not easily visible,” Decker says. “Carry a flashlight and use it to eyeball anything that feels out of round.”

Decker suggests checking every groove in three to five places, and going further up or down as you move from one groove to another to ensure you don’t miss irregular wear patterns, such as flatspotting.

The most common cause of irregular wear is misalignment. Having alignment done on a regular schedule or as soon as warning signs emerge can increase tire life by 30 percent, experts say. Jace Nixon, of Barr Nunn Transportation’s maintenance department, says, “We align the tractor if there are driver complaints of wear or vibration, and we align when we change steering tires, about every 110,000 miles.” Keeping a close eye on tire wear will give some indication how often alignment should be done. If wear is not corrected soon enough by alignment, it will continue to develop, despite corrective measures. All axles should be aligned, including the trailer’s. Common misalignment problems on the drives and trailer tires include feathering and push wear, a diagonal scuffing across the tire.

Sloppy tire mounting can also cause irregular wear. “If tires are not put in the concentric center of the wheel when mounted, they will cause the tire to go out of round quickly,” Coolidge says. Guide ribs on the tire where the wheel and rim meet, sometimes called gee-gee rings, indicate whether the tire has been properly mounted. If the rib is not 1/4 inch from the rim all the way around, the tire should be remounted.

Mechanical problems, such as a bearing going bad or a dragging brake, will also show in cupping and tread wear patterns. A misaligned drive train can cause shoulder wear. Flatspotting is a sign of a dragging brake.


SHOULD YOU ROTATE?

Rotation is not the answer to all problems exposed by tread wear patterns and depth, but it is useful in certain ways. When tires are mismatched, rotation is counter-productive.

Jose Sierra, an owner-operator for 13 years, believes strongly in rotation. “I use a criss-cross rotation on my drives and I am very happy with tire life,” says Sierra, who tracks tires from mounting to trade. “I rotate every six months.”

Heel and toe wear, found on drive tires when the trailing edge of a lug slips and snaps as it turns on corners or changes lanes, can be evened out by cross rotation, says Don Darden, a communications director for Bridgestone Firestone. “If heel and toe wear is the only irregular wear you have, cross-rotating drive tires, to reverse their direction of rotation, can help equalize wear patterns,” Darden says.

There are various patterns for rotation, limited by tread design differences and tread depth among steer, drive and trailer positions. Even retreads benefit from rotation, says Al Cohn, a marketing manager for Goodyear. Cohn recommends, “You should remove your drive tires by 4/32 if your trucks are in linehaul service and use first retreads as drive tires and second retreads as trailer tires.”

Allowing tires to get out of round not only reduces the life of the original tire, but also can make it impossible to recap if the casing is damaged. “Some fleets recap at 6/32,” says Harvey Brodsky, director of the Tire Retread Information Bureau. “But owner-operators are more likely to want to recap at 4/32. Below that, the tire is much more susceptible to damage and road hazard.

“Getting more than one recap out of a tire is a bonus. If you own your trailer, you can save a great deal of money by putting your first cap on the tractor and subsequent recaps on the trailer.”

Recapping or rotation at the first sign of a problem usually isn’t the best overall strategy, Decker recommends. “The owner-operator is better off to get first-life good wear pattern by close inspection and care rather than rotation to a drive axle,” he says.

A wear pattern sometimes is correctable if caught early enough, but if wear is an indicator of an underlying drivetrain, brake, bearing or suspension problem, rotation only masks the symptom. While the temptation is to run components until they break or totally wear out, replacing shocks and other suspension and brake parts on a schedule will yield improved tire life and fewer road repairs.

In some cases, automatic balancing systems can help reduce out-of-balance wear. “Brake drums can go out of balance in 50,000 miles,” Coolidge notes. “Balancing tires does not balance brake drums.” An automatic balancing system can offset brake drum imbalance. Tire warranties generally do not cover wear caused by out of balance conditions.


RECORDS

“You have to have a hands-on approach to tire management, and you have to keep good records,” says Michelin’s Jones. While record-keeping should be tailored to your operation, every tire records program should include manufacturer, type, wheel position and price. Also note truck mileage at installation. This will enable you to calculate cents per mile for each tire.

Record when the tire was taken out of service and whether it was recapped. If it was capped, note the position to which it was moved and record mileage for that tire at that position to give you a record of cap life. Continue this procedure for the life of every tire and every cap. In a year or so, you will have the level of detail necessary for making informed choices about brands, wheel positions and recaps.
If you want to take a more intensive approach, computer programs can help. Goodyear, for example, has a tire management tool for owner-operators with laptop or handheld computers. The company’s TVTRACK software, which retails for $499, tracks data on each tire and helps you calculate relevant costs.

Any method of keeping costs down should help the profitability of your operation. With complete records, you can pin down costs and upgrade your hands-on procedures to continue cutting costs.


RESOURCES

The Technology & Maintenance Council’s Recommended Practice 219, the Radial Tire Condition Analysis Guide, helps you interpret wear patterns. The guide can be purchased through TMC for $95 by calling (203) 838-7928.

The Tire Retread Information Bureau’s Industry Standards For Tire Retreading And Repairing explains developments in retreading technology and how to find quality retread facilities. Free copies should be available at retread facilities or by calling (408) 372-1917.


GETTING THE MOST FROM A REPAIR

One big bugaboo in any one-truck operation is tire repair – knowing when it’s practical and getting it done right.

Sidewall repairs on injuries up to 4 inches long and up to 3/4 inch wide, when done properly, “have a strength equal to that of the surrounding tire body,” says the Tire Retread Information Bureau, citing Tire and Rubber Association research. This is a drastic departure from 20 years ago, when sidewall damage generally meant the death of the tire. Better technology makes such repairs possible.

In the crown, 1 1/2-inch diameter injuries and nail holes up to 3 1/8 inch can be safely repaired, according to some tire repair material manufacturers. The tire should never be repaired on the rim.

Use the appropriate repair materials designed for tires, either radial or bias. All repairs should be done to the inside and outside of the wound. Not cleaning and filling the wound will cause belts to rust, even to loosen or separate.

A carbide cutter should be used to clean the wound. It should then be cemented and a vulcanizing rubber stem applied. The inner liner should then be buffed, cleaned and cemented. Only then should the proper repair material be applied to the inside of the tire.

Unless you’re familiar with the quality of work at a particular shop, it’s a good idea to observe the process. Watching the tire technician rather than getting a well-deserved nap may seem an unnecessary burden, but it can pay off in safety and longer tire life.

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