Tires troubles are among the top three causes of CSA violations, and with more of them on the truck and trailer than just about anything else other than lights, they can be difficult to manage.
Improper tread depth, according to Gary Schroeder, director of Cooper’s truck and bus tire business, is the most common tire-related CSA penalty.
There’s an old business idiom that says, “what gets measured gets managed,” and while the first line of defense in measuring tire health falls on pre- and post-trip inspections, below is a list of the Top 6 – The Super Six – causes of irregular and premature tire wear to aid in maintenance management practices.
Picking the wrong tire for the job
Tom Clauer, Yokohama’s manager of commercial and OTR product planning, says having a tire that is designed to handle the forces specific to operational demands is the first and most important decision when it comes to optimal tire performance.
“Wear, tread life, and damage resistance all are vital items that need to be considered when making this decision,” he says, adding the right tire on the wrong truck is also problematic.
“Many times, long-haul trucks supplement shorter regional, urban operations in a pinch. Once in a while, this is acceptable. However, over a period of time it can show advanced tire wear, not to mention equipment wear.”
Wheelbases and axle sets are engineered to handle specific operations and anything outside of their design parameters creates challenges.
For example, Scott Pall, Continental’s Northern U.S. sales manager for commercial vehicle tires, says using a fuel efficient long-haul drive tire in a local/regional application could cause tire wear from high torque or cut-and-chip damage because it’s not designed to withstand that type of application.
“Tire tread depth, groove geometry, tread compounds, and other engineering factors all play a role in tire wear,” he says.
Inadequate air pressure
Under the Federal Motor Carrier Safety Administration CSA program, a tire operating with less than 50 percent of its maximum pressure is considered flat – an eight point, an out-of-service violation.
Maintaining correct inflation pressure will not only keep your CSA scores down, but it is also one of the most effective things in positively impacting tire wear, casing life and overall tire performance.
“Both over-inflation and under-inflation can change a tire’s footprint, making it susceptible to premature, irregular wear,” Evan Perrow, senior product marketing manager for Goodyear, says, noting inflation levels should be checked daily when possible. “Keep in mind that temperature fluctuations can have an impact on tire inflation levels, too. Think of a tire on a truck that has been running in a hot area, such as the southwestern desert. The tire could run all day in 110-degree heat and then sit overnight in 60-degree weather, which could affect psi levels. It’s important to remain vigilant when monitoring tire pressure.”
“Under-inflation is the biggest issue in the industry,” adds Delvin Webb, Michelin Americas Truck Tires, U.S./Canada customer engineering support department manager. “It is the number one cause of premature tire removal.”
A tire is designed to contain air pressure, provide traction and driver comfort throughout its casing life, and Clauer says properly maintained air pressures will insure the life of the tread as well as the casing for retreading.
“A tire is a containment vessel,” Clauer says. “Air pressure is what carries the weight so it’s important that the air pressure is set correctly. Improper air pressure is a constant culprit in irregular wear, abbreviated tread life and premature tire failure.”
Prosser Carnegie, Continental’s North America head of product development for truck tires, says tires typically lose up to 2 percent of their air pressure every month.
When checking inflation levels, it’s also important to be sure tools are properly calibrated as usage conditions can cause a pressure gauge to lose accuracy beyond the two PSI manufacture’s tolerance range.
An inflation pressure mismatch of greater than five PSI will result in the two tires of a dual assembly being significantly different in circumference, Webb says, resulting in irregular wear and possible premature casing fatigue.
“A difference of 5 PSI between steer tires will cause the vehicle to pull to the side with the lower pressure,” he adds.
Schroeder says inflation levels should be based on a scale weight by axle and the load/inflation chart for that tire size, adding there are two scales for truck tires: One for singles and one for dual tires.
Improper mounting sets the stage for irregular wear
Tires that aren’t mounted correctly to the truck or trailer never stand a chance to reach their wear potential.
“It’s important the tire has been completely seated and is seated circumferentially even,” Clauer says. “A tire that has not been properly seated can created immediate irregular wear patterns and ride, handling and vibration issues.”
James Matarelli, Continental’s western U.S. sales manager for commercial vehicle tires, says if the tire is not seated properly to the wheel flange area, the tire and wheel assembly will have an “out-of-round” posture, creating wear.
“If, for some reason, the tire bead doesn’t fit into the wheel properly – for example, if the tire was not sufficiently lubed during installation – it will not properly center onto the wheel flange,” he says. “This prevents the tread from lying flat as the tire rolls forward and backward and causes uneven wear on the shoulders of the tire.”
Most major tire manufacturers have proper mounting procedures available on their websites. Additionally, organization’s such as the Tire Industry Association have developed training programs to insure service personnel are fully equipped to handle all mounting procedures for optimal tire performance.
Another item to consider when mounting a tire is to ensure tread depths match on both sides of the axle.
“Mismatched tires can lead to problems,” Perrow says. “For example, diameter differences of larger than a quarter-inch can create scrubbing patterns for the smaller of the two tires.”
Travis Despain, Continental’s Canada sales manager for commercial vehicle tires, says a difference as small as 4/32nds in tread depth can cause premature wear. He adds mounting tires from different manufactures can unintentionally cause a mismatch.
“In some cases, tires can have identical tread depth but a different overall diameter due to engineering differences,” he says.
Carnegie says if one tire in a dual position is damaged and requires premature replacement, fleets ideally should either replace both tires with matching new tires, or have an inventory of used tires on-hand from which to select that matches the remaining tire.
Tire imbalance and alignment
Wheel balancing can reduce ride complaints and vibrations, but it’s also instrumental in prolonging tread life and eliminating irregular wear.
“It’s also an easy way to check to there is no excessive run out due to the mounting process,” Clauer says.
Balance techniques, procedures and equipment vary, but Clauer says any attempt to balance is better than no attempt at all. However, he recommends starting “on the vehicle,” so the tire, wheel, hub and brake rotor/drum are balanced as a single unit.
You can’t talk about imbalance and irregular wear without mentioning alignment, which Webb says refers not only to the various angles of the steer axle geometry, but also to the tracking of all axles on a vehicle, including the trailer.
Alignment keeps everything going in a straight line, but also provides calculations to meet the needs the equipment components were designed to compensate for.
“These include inertia in highway speed turns, ease driver comfort and provide optimal wear of the tires,” Clauer says.
Rod Conner, Continental’s warranty and field services manager for technical customer services, says the steer tire is the best place to start when diagnosing alignment issues because irregular wear is most visible there. However, alignments at all wheel positions should be considered each inspection and service cycle and when tires are replaced.
“With 18-wheelers, a traditional front end alignment isn’t always enough,” Perrow says. “Drive axles must be aligned, too – making sure they are perpendicular to the chassis, and in the case of tandem axles, parallel to each other.”
“Trailers take a beating and are usually the last piece of equipment to receive any attention or maintenance,” Clauer adds. “Trailers are subject to damage to the tires, as well as other components, due to curbing, overrunning railroad tracks and other surface objects, including damage from intermodal functions.”
One other forgotten item in maintaining a good alignment program is to insure the fifth wheel is tight, set and well-lubricated.
TravelCenters of America Manager of Technical Development Homer Hogg says the fifth wheel should be lubricated at least every 90 days or 30,000 miles, whichever comes first.
“More frequent lubrication may be necessary if the truck operates in a frequent hook and unhook environment,” he adds. “[National Lubricating Grease Institute] No. 2 grease is recommended.”
Any part that moves wears, and Clauer says if during any maintenance procedure a technician can initiate even the slightest irregular movements in tie-rod ends, kingpins, wheel bearings or torque rods, “imagine what 4,000 to 10,000-plus pounds of weight on a single assembly can accomplish.”
“Waiting to replace any parts that shows signs of looseness damage, or wear can cause irreversible irregular wear damage to your tires,” he adds.
Despain says wear patterns typically seen with mechanical issues include spotty and diagonal wear.
Clauer says once a wear pattern gets is established, it will continue to worsen. He recommends shock absorbers be checked every maintenance service cycle and replaced at any signs of leaking fluid, replacing in pairs.
With factors like the quickness of a truck’s launch, harsh braking and sharp turns that skid trailers, drivers have a significant impact on tire maintenance, wear and failures.
“[Brake] skids remove generous amounts of material from tires,” Clauer says. “This missing material is called flat spotting. The best remedy for flat spotted tires is to have them buffed or retreaded. Trailer tires are most susceptible to these occurrences for multiple reasons. Insuring the power unit and trailer brakes are properly set at each hook will prolong the life of all tires dramatically.”
Clauer adds drivers are also the first to see most irregularities, noting pre-checks are the best place to begin thorough inspections.
“Tires will tell you what is happening to them and drivers should be knowledgeable to what the signs and indicators are to understand what the tire is telling them,” he says. “This is the front line in tire maintenance and the most efficient.”
One element of tire wear drivers have complete control over is how they drive the truck under less than ideal conditions.
The primary purpose of a shock absorber is to keep the tires in contact with the road, but in order to do that they dampen road irregularities.
“It’s not just about the ride,” Clauer adds. “Once a tire takes a bump – a surface irregularity – all or part of the tire loses contact with the road surface. Every time it happens – this includes tread flexing – it creates wear.”
Webb recommends training drivers to check air pressure and tire condition during their pre- and post-trip inspections and maintenance staff should support those inspections with immediate repairs of tires as-needed.
“Operators are strongly encouraged to be aware not only of their tires’ visual condition and inflation pressure, but also of any change in dynamic performance such as increased air loss, noise or vibration, which could be an indication that the tires need to be removed from service to prevent tire failure,” he says. “While on the road, drivers should be vigilant for road conditions, debris and other driving behaviors that may lead to premature tire degradation.”