Proper tire maintenance is an important safety function that is often neglected. Yet, maintaining tires is essential because if they can’t perform as designed, vehicle handling, traction, braking, load-carrying capability and fuel economy is affected.
Photo credit: Photo courtesy of Michelin
A critical factor for getting the most out of tires is to maintain the proper inflation pressure for a given tire size and load.
Photo credit: Photo courtesy of Goodyear
Maintaining the correct tire pressure is so challenging because of the many factors working against maintaining inflation pressure.
Photo credit: Graphic courtesy of Aperia
The federal government mandates that steer tires be pulled when they reach 4/32” remaining tread depth. The limit for drive and trailer tires is 2/3”.
Photo credit: Photo courtesy of TravelCenters of America
TPMS technology continuously monitors the air pressure in each tire and provides real-time tire status information via an in-vehicle display. TPMS technology continuously monitors the air pressure in each tire and provides real-time tire status information via an in-vehicle display.
Photo credit: Photo courtesy of Bendix
In any pre-alignment check, the vehicle should be raised and the suspension inspected for problems like damaged springs, worn kingpins, loose bearings or worn steering linkage.
Photo credit: Photo courtesy of Bee Line
Truck tire changers are designed to be fast and efficient and replace outdated manual tire changing methods.
Photo credit: Photo courtesy of BendPak-Ranger
New generation tire changers offer increased speed, safety and less risk of bead damage when changing difficult tires like the wide base modes.
Photo credit: Photo courtesy of RAV America
OSHA regulation 29 CFR 1910.177 mandates that any tire inflated off the vehicle must be inflated inside a safety cage or secured with a restraint device to help protect bystanders from rapidly deflating (exploding) tires.
Photo credit: Photo courtesy of BendPak-Ranger
A successful tire program means a lot to a fleet’s overall financial success because tires are typically one of its top three expenditures. The foundation for such a program begins with selecting the best tire for the intended application, followed by incorporation of a tire management program that includes protocols for tire inspections, PMs and inspection intervals into a fleet’s preventive maintenance program.
Neglecting proper tire maintenance can affect vehicle availability and impact operating costs.
This article is a roundup of advice for getting the most out of tire and wheels.
“Do not be tempted to purchase the least expensive tire available, as this is unlikely to result in overall tire cost reductions,” warn officials with Pressure Systems International (www.psi-atis.com), the manufacturer of the Meritor Tire Inflation System by PSI. “A specific tire make/model may have a high initial cost but if it averages higher miles to removal, along with more retreads per casing, then the result is a big reduction in overall tire cost per mile.”
They add that it is important to choose the best tire for the specific service vocation – no easy task as there are many available tire makes/models to consider for steer, drive and trailer tires.
“Since no two fleets are the same, the only way to determine which tire is optimum for a specific application and wheel position is through real-world testing,” the officials say. “Working with your tire professional is the best way to develop a test program and track a statistically valid sample size.”
Today’s truck tires are being designed to provide service greater than the tread will last. By retreading the tire casing, a fleet can reap the benefits of these highly designed tires.
One benefit is lowering money spent on tires. It costs about 30 to 50 percent of a new tire to retread a tire casing.
Retreading – which can be done for both regular and wide base tires – involves removing used tire treads and applying freshly vulcanized new treads so that the body of the tire can be reused. Application-specific tread designs are available.
Moreover, using retreads makes an environmental contribution in terms of the more effective utilization of natural resources. Oil is a major component in the rubber compounds used in tires. A retread uses about one-third of the oil needed for a new tire.
When it is time to choose a retread, not only is there a choice of a specific tread design but there are several compounds to select from as well,” note Pressure Systems International officials. Fuel efficient compounds, high mileage and high traction are typical options.
“You also need to determine what is the maximum casing age where retreading is a win-win option in your fleet. Some fleets say a five-year-old casing is the limit for retreads while other choose six or seven years. This choice depends on the results of a scrap tire pile analysis.”
The officials also recommend determining the target tread depth when tires should come out of service and be sent to the retreader.
“Running tires down to the legal DOT limits of 4/32” for steers and 2/32” for drives and trailers can lead to casing damage and that will adversely affect the tire casing for retreading. There is a sweet spot when it comes to tread depth pull points for every fleet.”
Keeping tires properly inflated is the single most critical factor for getting the most out of tires. By maintaining the proper inflation pressure for a given tire size and load, tires not only last longer, they are safer.
In addition to affecting rolling resistance and thus fuel economy, tire inflation pressures also influence traction, handling, braking distance, load-carrying capability and smoothness of the ride, says Jeff Kritzer, senior vice president, sales and marketing for BendPak-Ranger (www.bendpak.com). Thus, inspection and maintenance plays a very critical roll.
BendPak is a leading producer of lifting systems, pipe-benders and air compressors. Ranger offers tire and wheel service equipment; hydraulic jacks, cranes and stands; tool storage and benches; spray wash systems; and a variety of specialty service tools.
“Studies of tire safety show that maintaining proper tire pressure, observing tire and vehicle load limits, avoiding road hazards and inspecting tires for damage or wear are the most important things you can do to avoid tire failure and increase the life of your tires,” he says.
Tires flex when they roll, which bends the tire’s rubber and steel (used within the rubber to provide additional operating characteristics) in the sidewall of the tire. This flexing generates heat. Wear is the result of friction created between the road’s surface and the tread as the tire rolls along. Heat is a tire’s worst enemy.
A tire that is improperly inflated doesn’t roll as smoothly or as easily as it was designed to.
Underinflation or overinflation can cause uneven tread wear, sidewall damage, a rough ride, poor handling and traction and poor fuel mileage, explains Kritzer. “Most tires will naturally lose air over time but air pressure can also decrease rapidly and unexpectedly if driving over potholes or other objects, or if periodic contact with curbs occurs while parking. Even minor differences in air pressure can cost fleets valuable profits.
“It is important for fleets to incorporate and maintain recurring vehicle checks to assure all tires are inspected and properly maintained at all times.”
Because improper inflation shortens tread life, tires will have to be changed more often. Along with the expense of purchasing replacement tires, there are the additional costs for tire service and vehicle downtime. Industry studies have shown that cost per mile almost doubles when tires - whether original or retreaded – are pulled early because of uneven or rapid tread wear.
OTHER AFFECTING FACTORS
Most fleets know that tire pressure affects fuel economy, say officials at Innovative Products of America (www.ipatools.com), a company specializing in the development of innovative tools and equipment. What is often overlooked are the synergistic effects of dual tires mismatched by fractions of an inch, tire pressures off by just a few psi and the resulting inflation of operating costs.
“The advent of tire pressure monitoring systems (TPMS) and tire inflation systems, as well as low rolling resistance tires, have helped in these areas, but unless your shop is following very important preventative maintenance procedures with accurate equipment, these new technologies are being effectively sabotaged.”
A major reason even the most well intentioned tire programs fail to achieve results is due to inaccuracy of pressure gauges as a whole, they say.
“Tires are engineered with a certain pressure range in mind that creates the optimal rolling resistance for the advertised savings in fuel costs. Verifying and maintaining proper inflation is not only a matter of habit and attention to detail, but requires precision equipment.”
When comparing two brand new tire gauges from the same manufacturer, accuracy often differs up to 3 percent right out of the box, observe the officials. This only compounds the problem as a gauge with +/- 3 percent accuracy will shift the air pressure reading by as much as 3.6 psi per tire at 120 psi target inflation.
In this example, two tires on the same axle could read 120 psi on the gauge, while in fact ending up 7.2 psi off.
“While automatic tire inflation and tire pressure monitoring systems can assist in tracking problems on vehicles in service, proper inflation before the vehicle leaves the shop, assured by using highly accurate air pressure gauges, is very important to maximize the tire investment.”
“In the big picture of fleet operations, the smallest details – a few PSI of tire pressure, for instance – can make a huge difference,” observes TJ Thomas, director of marketing and customer solutions, Controls group, Bendix Commercial Vehicle Systems (www.bendix.com). “Running at the right pressure has a major impact on crucial concerns like safety, uptime, tire costs and fuel consumption.”
Bendix develops and supplies active safety technologies, energy management solutions and air brake charging and control systems and components for commercial vehicles throughout North America.
Establishing a comprehensive tire management strategy should begin with a look at the fleet’s current tire practices and key metrics, he says. How often does a fleet replace tires; how much time and expense are invested in repairing tires; how regular are roadside breakdowns due to tire failure?
“Specific questions and metrics will vary from fleet to fleet, but noting three to five key tire metrics is important to tracking the effectiveness of a tire management strategy over time. Many fleets already gather this type of information, so establishing a performance baseline will simply involve making sure the methods of collecting the data are up to date.
“With this information, fleets can define their needs and develop a strategy of best practices to address them, including tire replacement, retreading and pressure-checking schedules. A tire management plan also includes continued data collection and analysis to measure ROI.”
A TPMS typically presents “the best option for meeting the daily tire pressure checks that are absolutely critical to the success of a tire management strategy,” maintains Thomas. “Although drivers and technicians could be equipped with tire gauges to manually check each tire, this is most often prohibitively time-intensive and fails to address changing road conditions that affect pressure during operation.”
A TPMS provides real-time tire status information and alerts to drivers and maintenance technicians through wheel-end sensors.
“An effective tire management strategy must emphasize the importance of timely responses to TPMS alerts,” he stresses. “Low pressure alerts need to be addressed the same day and not postponed until a regular weekly checkup or other preventive maintenance cycle.”
There’s a lot at stake, he points out. Studies have shown that almost half of all emergency service road calls are tire related, and underinflation and excessive heat are responsible for 90 percent of tire failures.
Furthermore, he says Technology & Maintenance Council (TMC) research has shown that tire underinflation by as little as 10 percent can result in a 1.5 percent drop in fuel economy and underinflation by 20 percent results in a 30 percent reduction in tire life. Underinflated tires are also considered violations in Compliance, Safety, Accountability (CSA) scoring.
Dual tires are also plagued by a whole host of issues that arise from the nature of two tires mounted to a conjoined wheel assembly, Innovative Products of America officials say. Even a size differential as small as 1/2” in diameter between a mated pair can shift a significant amount of extra weight to the larger tire. This will increase both tread wear and heat on the larger tire, directly reducing its lifespan.
While it may appear as though the larger tire is taking the brunt of the abuse here, consider that the tires must travel the same distance since they are bolted together. Therefore, the smaller tire is dragged over the ground in minute intervals per every revolution as its circumference is less than the larger tire.
“This effect is compounded over distance, as just a 1/2” variance results in the smaller tire being dragged 5.2’ per mile. This additional wear not only reduces the lifespan of the smaller tire, but also increases rolling resistance that serves to reduce fuel economy.
“For both of the tires in this scenario, the chance of a catastrophic failure is greatly increased, leading to expensive road calls and permanent damage to the tire casing preventing future retreads.”
Proper tire maintenance also requires that, along with using the same tire size and air pressure, dual tires need to have similar tread patterns and tread designs.
Vehicle alignment is another element to promoting long tire life and getting more miles per gallon. Consistently practicing thorough pre-alignment inspections can “significantly decrease your chances of overlooking a problem that could cause your vehicles to have issues later, which could, in turn, cost your business money,” says Tricia Kane with the Bee Line Company (www.beeline-co.com), a manufacturer of computer laser wheel alignment, on-truck tire balancing and frame correction equipment for heavy duty trucks and trailers.
The first step in any pre-alignment inspection is to check and record the “cold” inflation pressure on each tire, typically after the vehicle has been at rest for several hours, she says. Both steer tires should have roughly the same pressure, as should all drive tires and all trailer tires when compared to each other.
“Remember, no matter how precisely aligned the camber, caster, toe and tracking angles, the vehicle will still pull if there is uneven tire pressure.”
Next steps involve checking the tires for irregular wear, including fast wear, feather wear, cupping, diagonal wear, rapid shoulder wear and one-sided wear, says Kane. The type of tire wear patterns can indicate specific alignment problems. Also, make sure to check for problems like damaged springs, worn kingpins, loose bearings or worn steering linkage in the suspension.
“While all inspections may not be necessary, properly executed checks ensure that each and every vehicle serviced in your bay is evaluated in the same way.”
Wheel alignment is the positioning of the interrelated angles of a front suspension, rear axle or housing to give the maximum amount of tire life, steering ease, steering stability and increased life of suspension components, Bee Line’s Kane explains. Improper wheel alignment results in excessive or irregular tire wear, hard steering, poor drivability and premature failure of suspension parts.
Several alignment factors must be considered to achieve proper wheel alignment, she says. The top four factors are: toe, tracking, camber and caster.
Toe and tracking
These are the two most critical alignment settings for front end tire wear. Toe is adjustable to reduce tire wear and shimmy in the steering wheel. Excess or too little toe will make the front wheels fight each other, resulting in feathering, diagonal wear or excessive shoulder wear. An out-of-toe condition leads to rapid tire wear.
Tracking misalignment also will cause inside outside wear of the steer tires. Tracking, or thrust, is gauged relative to the vehicle centerline.
Camber and caster
There are the third and fourth most critical alignment settings for front end tire wear. Camber – the inward or outward tilt of the top of the wheel – is important for several reasons. Its main purpose is to keep the tire flat on the road while the vehicle is loaded and in motion. If camber is excessive, it will create shoulder wear.
Caster is the forward or rearward tilt of the kingpin. Extreme caster settings can cause handling problems, leading to driver fatigue.
Wheel balancing and proper wheel alignment are other critical service aspects that affect tire longevity, Kritzer of BendPak-Ranger points out. The most common result of an unbalanced wheel or an alignment not within OEM specifications is excessive vibration and uneven tire wear.
To avoid excessive vibration or shaking of the vehicle as it rolls down the road, he says tires “must be properly balanced. This is achieved by positioning wheel weights on the wheel assembly to counterbalance heavy spots on the wheel or abnormalities of the tire.
“A wheel alignment adjusts the angles of the wheels so that they are positioned correctly relative to the vehicle’s frame. This adjustment maximizes tire life and prevents the vehicle from veering to the right or left while driving on a straight, level road.”
There is also the matter of proper bead seating and inflation procedures, he adds. As mandated by OSHA’s 29 CFR 1910.177, any tire inflated off the vehicle must be inflated inside a safety cage or secured with a restraint device to help protect bystanders from rapidly deflating (exploding) tires.
“Inflated tires contain a large amount of stored energy. The sidewall of a typical commercial vehicle tire has more than 34 tons of force acting on it. Although todays OEM tires are designed to withstand these extreme forces, when damaged or extremely worn, tires are subject to fail.
“When a tire ruptures, the force can be released explosively at an angle of up to 45-degrees from the rupture, resulting in a destructive air blast and the sudden release and ejection of high-speed projectiles. Inflation cages are designed to contain the blast and to absorb some of the energy from the rapid discharge of air from the tire and wheel assembly.”
To see the destructive force a tire explosion is cable of, view Ranger’s inflation cage video at: www.bendpak.com/Videos/Ranger-Inflation-Cages.
Servicing truck tires is a proficiency that only conscientious and properly trained and qualified technicians should attempt, stresses Kritzer of BendPak-Ranger. Any business involved in tire service and repair is required to understand and follow all OSHA work regulations.
When it comes to heavy duty tire service, “there is no room for errors or shortcuts,” he says. No one should attempt to service any wheel assembly without proper training and the recommended tools and equipment need to be on hand and used according to manufacturer’s instructions.”
Most wheel, tire and service equipment manufacturers offer service manuals and other training materials for increasing operator awareness and safety, he goes on. “Be sure all of your employees stay up-to-date on proper service procedures and always maintain and keep current instructional materials in the work area for easy reference.”
Nick McCullough of RAV America (www.ravamerica.com), a distributor of Ravaglioli wheel service equipment, notes that the new generation tire changers represent a “breakthrough in tire changer technology and offer increased speed, safety, versatility and less risk of bead damage” when changing difficult tires like wide base tires.
These machines do away with the labor-intensive task of manually lifting of heavy tire and wheel assemblies, breaking beads with a hammer and mounting or demounting using tire bars or irons, he says. They are user friendly for simple operation and employ hydraulics to push the tire on and off, improving labor efficiency.
The industrial quality of the machines insure reliable service over an extended life span and many are highly versatile and will handle most difficult types of tires, he adds.
The payback from all aspects of an effective tire maintenance program is clear. Not managing this important area effectively adds up quickly to higher fuel, tire and labor costs, plus increased vehicle downtime and loss of fleet productivity.