Maximizing tread life is all about the contact patch — literally where the rubber meets the road. Pavement is abrasive by design. That’s how you get friction between the tire and the road surface — in other words, traction. But excessive friction or uneven contact between the pavement and the tire will cause tread to wear away faster than you should. It’s important that you do all you can to keep your tires running straight and true.
Before we get to alignment and pressure management, let’s look at the tires themselves. Rib-type treads will generally wear longer than lug-type treads because there’s less movement of the tread blocks between the body of the tire and the road. Lug treads can squirm and wiggle under load, and that movement translates into scrubbing, which as the word implies, scrubs away tread rubber.
Deeper treads squirm more than shallow treads, and thus wear away faster. It may seem like tires with deeper tread last longer, but that’s only because there’s more rubber there to begin with. But if you measure tread loss by miles per 32nd of an inch of rubber, you’ll notice that deeper treads wear faster when the tread is new (deep) and the wear begins to abate as the tread becomes shallower.
Tread rubber compounds can affect wear rates, too. Compounds are often tuned for specific applications and wheel positions.
“Tread rubber compounding affects tread life in a variety of ways, and significantly influences tire performance attributes such as tread wear, rolling resistance, resistance to cutting and chipping, and traction — all of which play a role in tire tread life,” says Gary Schroeder, director of commercial vehicle and global OEM sales for Cooper Tire & Rubber Company, assigned to the Roadmaster brand. “Ensuring that you have the correct tire for your service type can help maximize tire life. A tire designed for long haul truck service will not always do well in a mixed-service application or in an urban environment.”
Right from the start
Proper mounting and installation will prevent some types of premature wear. Concentric mounting of the tire on the wheel will prevent radial-runout, or the egg-shaped rotation pattern common when the tire isn’t properly centered in the wheel. You can ensure the tire is properly seated by checking to see that the distance between the rim flange and the tire’s aligning ring is uniform around the complete circumference of the tire.
“With the bead seated against the rim, the distance from the seating ring to the rim should be measured at four different points that are 90 degrees apart around the rim,” suggests Sherrell Watson of GCR Tires & Service, a division of Bridgestone Americas Tire Operations. “The distance between the ring and the rim should be the same at all four points.”
Much irregular wear, and some ride vibration conditions, can be traced back to this installation problem.
Another installation-related problem is lateral run-out, defined by the American Trucking Association’s Technology & Maintenance Council as side-to-side movement of the rotating assembly. For a tire or wheel, its effect is to lead a vehicle alternately left and right as it rolls along, creating the perception of a shimmy or wobble.
“Once the tire is installed, a run-out gauge should be used to confirm the trueness of the wheel assembly,” says Schroeder. “If it’s not running true, something is amiss. If you ignore this detail when installing wheels you can expect problems down the road.”
Another common installation mistake is mismatched dual tires. Even the smallest difference in inflation pressure and tire height and diameter can wreck one or both tires, says Watson.
“Paying close attention to tread depths between dual positions and ensuring that they are no greater than 4/32 different in tread can ensure that the tires are able to perform together optimally,” she says.
According to Schroeder, a differential of just 5 psi across a pair of identical tires in a dual assembly can result in the tire with the lower inflation pres-sure having a circumference that is 10/32 inches smaller.
“During every rotation cycle, the smaller circumference tire will scuff ahead to keep up with the tire with more inflation,” he explains. “Tires rotate approximately 500 times per mile, so simple math suggests 500 times 10/32 inches equals 156.3 inches per mile, or 13 feet per mile. How many feet is that per day or per year?”
A similar situation can develop when rotating tires mid-life. Some fleets rotate tires routinely, while others do it as the need arises to offset uneven wear. Changing the direction of rotation has a tendency to even out heel/toe wear on the shoulders of drive tires and erratic wear on the shoulders of trailer tires. Steer tires are normally rotated side-to-side, which changes the direction of rotation and helps even out wear. Michelin recommends rotating the tires as necessary.
“If the tires are wearing evenly, there is no need to rotate,” says Sharon Cowart, director of product marketing, Michelin Americas Truck Tires. “If irregular wear becomes apparent or if the wear rate on the tires is perceptibly different (from axle to axle for drive tires and side to side for steer tires), then the tires should be rotated in such a manner as to alleviate the condition.”
Note that directional tires are the only tires that should not change the direction of rotation when repositioning tires, and beware of mismatch situations.
Straight and true
Many tire problems can be traced to mechanical conditions on the vehicle. For the best tire performance, vehicles must be properly maintained, including alignment.
“Alignment 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,” Cowart notes. “The dual purpose of proper alignment is to minimize tire wear and to maximize predictable vehicle handling and driver control.”
Vehicle misalignment often shows up as an irregular wear condition on steer tires, such as feather wear, rapid wear on one shoulder and one-sided wear.
“If the left and right steer tires have the opposite wear pattern (i.e. the out-side shoulders of both tires is worn fast), then a toe-in or toe-out condition is present,” Schroeder says. “If the left and right steer tires have the same wear pattern (i.e. inside shoulder of left steer and outside shoulder of right steer worn fast), then you have a misaligned drive axle.”
To keep tires wearing evenly, TMC suggests vehicle alignment should be checked every 80,000 to 100,000 miles or every 12-18 months.
Keep up the pressure
We saved the most obvious robber of tread life for last: inflation pressure.
Simply put, tires are designed to operate at a certain inflation pressure determined by the tire size and the load it carries. Deviations from the defined pressure will have consequences for tread life and possibly casing integrity.
Overinflating drive and trailer tires is common practice for two reasons; running 100 psi rather than the required 75-85 psi (as noted in most load and inflation tables for a dual tire loaded to 4,250 lbs) provides a margin for error in between pressure checks, and it is widely believed to improve fuel efficiency by making the tire harder therefore lowering rolling resistance.
“Nobody wants to run their tires at the low end of that spread because fuel economy suffers,” says Al Cohn, director of new market development and engineering support at Pressure Systems International. “Fuel economy always trumps tire wear.”
Automatic tire inflation systems, such as the Meritor Tire Inflation System by PSI, Hendrickson TireMaax, Stemco Aeris, Dana Spicer Optimized Tire Pressure Management System and the Halo tire inflation device from Aperia Technologies, can help maintain tire pressure to a preset value, alleviating some of the concern of tires losing pressure over time or due to small leaks. Operating at the design inflation pressure will extend tread life if no other harmful influences are present. Running higher pressures may improve fuel efficiency slightly, but it can be equally detrimental to tread life and tire wear.
While tire inflation systems will help maintain tire pressure, tire pressure monitoring systems from companies such as Bendix SmarTire and Truck System Technologies, can provide up-to-the-minute reporting on actual in-flation pressure. In addition, many, such as Tire Stamp’s Tire Vigil and Advantage PressurePro, provide reports on inflation pressure that can be invaluable in tracking tire wear and mileage.
“TPMS solutions are electronic systems that capture tire data and report findings to the drivers and fleet managers, so they can best manage tire maintenance,” says Vanessa Hargrave, CMO, Advantage PressurePro. “At their most fundamental level, they alert drivers to under-inflated tires, which prevents irregular tread wear and possibly catastrophic tire failure.”
If all that tracking and measuring is a bit much for your operation, Ventech offers a device called Pneuscan that takes care of all of that and more. It’s a drive-over installation that measures inflation pressure by comparing the contact patch against an optimal sample, and it measures tread depth, irregular wear and even vehicle alignment. Data is captured by sensors and recorded along with the unit number or license plate of the vehicle. Any out-of-normal conditions are reported immediately.
“Drivers do not have to leave the vehicle, they just drive over the plate and all the information for every wheel position is instantly recorded,” says Alex Rodriguez, sales manager at Ventech. “It’s won’t re-inflate your tires, but it will alert you to problems that can cause increased tire wear.”