The number of tire-related issues and roadside events could be significantly reduced by maintaining proper tire pressure inspections; ultimately, downtime on the side of the road can be reduced. If a tire is 20% below recommended pressure, it must be considered flat.
“Maintaining proper tire air pressure is probably the single most important maintenance activity that a fleet can do to maximize its investment in tires,” says Sharon Cowart, product marketing director for Michelin Americas Truck Tires. “Driving on tires that do not have proper inflation can be dangerous and can cause tire damage. The correct inflation pressures must incorporate many factors including load, speed, road surface and handling.”
Cowart went on to explain that if a fleet invests in low rolling resistant, fuel-efficient tires and doesn’t maintain the optimum inflation pressure, the tires most likely will not meet the fuel efficiency expectations. Additionally, tire wear is dependent on the tire’s footprint on the ground when running. Both under- and overinflation can affect the footprint shape, causing irregular wear and premature removal, reducing the service life of the tire.
“Improper tire inflation pressure impacts the contact patch of the tire’s tread, causing tread to wear more quickly or irregularly across the tire,” says Jason Evans, director of store operations for GCR Tires and Service. “This can increase the rolling resistance of a tire, impacting fuel efficiency and subsequently the bottom line of a fleet.”
Evans stresses that it is crucial to ensure that tires are running at peak performance. He recommends that drivers assess tire pressure each day before operating a vehicle using an accurate tire pressure gauge.
Improper air pressure can also lead to or aggravate many different types of wear patterns.
“Most commonly, having too much air can lead to fast wear in the center of the tread,” explains Juan Britos of senior technical service at Hankook. “whereas having too little air can lead to fast wear on both shoulders. Regular air pressure checks, pre-trip inspections by drivers, yard checks, and alignment checks are all good maintenance practices to assure good tire performance. Carrying a new calibrated air pressure gauge is key to getting proper air pressure readings.”
Britos also recommended that scrap analysis can reveal possible wide spread issues within a fleet. Alignment, maintenance, application and driver abuse can all be found with a scrap analysis as well.
According to the Technology & Maintenance Council of the American Trucking Associations, a constant 20% underinflation in a commercial vehicle tire increases tread wear by 25% and reduces the tire lifetime by 30%, which results in significant increase in tire costs for a fleet. It also increases fuel costs—underinflation of just 10 PSI reduces fuel economy by 1%.
“Since air is what carries the load, tire underinflation is a big issue,” says Al Cohn, director of new market development and engineering support for Pressure Systems International (PSI). “When tires run underinflated, the tire footprint is no longer optimal. There is actually 18% more rubber on the road on a fully loaded tire run at 70 PSI versus 100 PSI. The excessive heat due to sidewall flexings because of running underinflated in combination with more rubber on the road, leads to premature tire removal.”
Cowart agrees: “Underinflation is the number one cause of premature tire removal. With the advancement in today’s radial casing, it is virtually impossible to determine if a tire is properly inflated without using a pressure gauge. Periodically calibrate the gauges using a master gauge. Over time, usage conditions can cause a pressure gauge to loose accuracy beyond the 2 PSI manufactures tolerance range.”
“A tire that is underinflated by as little as 2% can exhibit irregular wear and other tire issues,” cautions Travis Despain, Canada region sales manager for Continental Commercial Vehicle Tires. “Worn valve stems and temperature changes can increase the amount of pressure loss, as can nail holes and other tire damage from demanding applications. Fleets should check their tire pressure at least once a week to help extend the life of their tires. One of the quickest and easiest methods of checking tire pressure data is to invest in tire pressure monitoring system such as the ContiPressureCheck or ContiConnect digital tire-monitoring platform.”
Having overinflated tires creates its own set of problems, including increasing the likelihood of crown cuts, impacting breaks, punctures, and shock damage resulting from the decrease of sidewall flexing and an increase in firmness of the tread surface.
“Maintain all tires at the fleet target inflation pressure based on the manufacturers’ application data book for the particular axle load to decrease the probability of potential casing damage,” recommends Raul Garcia of Falken Tire product planning for commercial truck and bus tires. “A change in the contact patch footprint could result in a reduction of traction and tread life. Air pressure directly affects the contact patch between the tire and road surface. A healthy footprint can maximize the life of the tire by distributing tire stress across a broader surface area.”
Using the right tires
It’s vital to use the right tires for the application and to properly maintain them.
“The most common issues that we see with fleet’s tires are caused by variances in maintenance practices,” explains Leo Hussey, a key account manager for Continental Commercial Vehicle Tires. “If proper air pressures, speeds, loads, pull points, etc., are not maintained during the life of a fleet’s tires, that will drastically affect the success of a tire and retread program.”
“Mismatches between identical tires can be caused by differences in air pressure, causing irregular wear in a ‘tall tire, short tire’ pattern,” cautions Prosser Carnegie, Continental’s North America head of product development for truck tires. “Variances as small as 5 PSI can cause the tires to be mismatched. This type of mismatch can occur even when the tire make, model, tread depth, and diameter are identical. A difference in air pressure between two dual position tires is easy to fix, but frequently goes unnoticed until it causes visible tire wear.”
Additionally, it’s crucial to make sure tires in a dual position match. “If one tire in a dual position is damaged and requires premature replacement, the fleet should ideally either replace both tires with matching new tires,” Carnegie notes, “or have an inventory of used tires on hand from which to select one that matches the remaining tire. Otherwise you may reduce the life of the tires significantly,”
Scrap tire revelations
The primary objective of doing a scrap tire analysis is to identify the cause of removal by looking at patterns or repeated damages, according to Michelin’s Cowart.
“Scrap tire analysis can help a fleet identify improper maintenance practices if the tire exhibits damage associated with under- or overinflation, or with pairing mismatched tires,” Continental’s Despain adds.
Once the analysis is completed and the causes are identified, the fleet can then focus on corrective actions. The results of tire inspections can say a lot about operations, help prevent premature tire loss and indicate the need for tire or vehicle repairs or adjustments in vehicle operation. If an operation utilizes their vehicle maintenance reporting and scrap analysis, they should be able to narrow down the crucial factors in choosing a relevant selection for their specific application.
One important step is to analyze the history of scrap tires and evaluate and determine the type of tire damage. Michelin’s Cowart lists the following items as key to the evaluation: manufacturer, tire design, tire size, ply rating, age, number of retreads, casing condition, tread depth, load distribution and alignment.
“A trusted tire service provider can incorporate scrap tire analysis into ongoing service, sharing insights across larger data sets that can drive positive improvements for a fleet,” GCR’s Evans suggests. “For example, for a long-haul flatbed fleet that typically carries lighter loads, such as fiber insulation, tire inflation pressure may need to be substantially lower for the 15,000-lb. load versus a 40,000-lb. load.”
“The added value of scrap tire analysis comes from understanding preventative measures built in the tire features to combat elements causing these failures,” Falken’s Garcia says. “Healthy maintenance schedules go a long way. Inspecting tires and reacting to early indicators of tire issues can help fleet managers maximize the value of their tires. Underinflated tires can increase the wear rate of a tire, while damaging the casing by adding unnecessary stress.”
Auto inflation pressure monitoring
Charles Timmerman, director of service marketing for Michelin Americas Truck Tires, touts Michelin Auto Inflate, which he says utilizes automatic tire inflation technology to maintain pressure on drive and trailer tires.
“Michelin Auto Inflate is a wheel-mounted tire management solution that allows fleets to automatically maintain optimal tire pressure as you drive,” Timmerman explains. “Michelin Auto Inflate, powered by Halo in association with Aperia Technologies Inc., can save fleets an estimated $2,400 per tractor-trailer annually by reducing tire-related downtime events, extending tire life, improving fuel economy and increasing safety.”
Another important aspect of keeping tires properly inflated is maintaining the proper temperature. “Underinflation can cause excessive tire heat,” says Jon Intagliata, product manager for tire pressure monitoring with Bendix Commercial Vehicle Systems. “Most experts consider 195 degrees Fahrenheit as the ‘line in the sand’ when it comes to tire temperature. Beyond that point, the temperature will start impacting tire life. At 250 degrees, a tire will start to lose structural strength, could begin experiencing tread reversion, and the tire will begin to lose strength.
“A general rule of thumb is that for every 10-degree increase in tire temperature, a tire’s pressure will increase by 2 PSI,” he continued. “Bendix doesn’t recommend letting air out of a hot tire, because doing so increases the chance that when the tire cools, it will be underinflated. The SmarTire Tire Pressure Monitoring System by Bendix CVS uses wheel-mounted sensors—which provide the most accurate data while remaining protected from external hazards—to continuously monitor and provide real-time information on the pressure and temperature of each tire on a tractor and/or trailer.”
Tiona Campbell, program manager for Hendrickson’s controls business unit, reiterates that underinflation is the number one problem that cmes up with trailer tires. “If the carcass is damaged, retreading the tire is no longer a viable option, which can add hundreds of dollars to the cost of servicing the tire,” Campbell says. “Even if the carcass is spared, the heat and deflection of an underinflated tire leads to increased wear, reduced life and a corresponding drop in fuel economy. Testing shows that a 5 PSI difference between duals creates a 5/16-in. difference in tire circumference—meaning the larger tire essentially drags the smaller for 13 feet every mile.”
Campbell points to Hendrickson’s Tiremaax Pro as a solution. “It’s an advanced automatic tire pressure control system for the trailer industry that is capable of active inflation, relieving and equalizing, minimizing costly tire wear, improving productivity and increasing fuel mileage,” Campbell explains. “In addition, it equalizes the pressure at all wheel positions by using special valves in hubcaps that allow air to flow in both directions.”
“Tracking tire rotations or replacements may not seem monumental when considering just one vehicle, but for an entire fleet, it’s not a simple task,” says Ozzie Flores, product manager with Teletrac Navman. “Teletrac Navman’s telematics solutions can be installed in every vehicle to gather critical data about performance, providing managers with insights around equipment utilization, maintenance and driver behavior to inform decisions that can impact tire wear.”