Trucks are taking to city streets like never before, as rising e-commerce demand sees growth in everything from courier fleets to white glove delivery services.
It’s enough to make a tire buyer cry.
The new business is certainly welcome, but these are hardly welcoming environments for treads and casings. Unlike the steady wear of longhaul or regional trucking, urban tires face more than their fair share of the stops, twists and turns that translate into aggressive wear.
Even the road surfaces themselves conspire against tires.
“Road surface material differs from what you would find on the interstate system — more abrasive and less maintained. In many cases, routes can include asphalt, concrete, gravel, tailings, and even dirt,” explains Tom Clauer, Yokohama Tire’s senior manager – commercial product planning. “Each of these have differing effects on tires.”
Waste collection vehicles represent some of the harshest applications given the repeated start-stop-start cycles along their residential routes. But there are also courier vans that might make dozens of stops per shift. Some drivers seem to bounce against curbs as if the poured concrete is an extension of a truck’s braking system.
“In an urban application, some of the main factors that reduce a tire’s life are stop and go, frequent cornering and tight maneuvers, and frequent contact with curbs. Stop and go applications generate heat in the tire, especially in the tread and bead area. They can also lead to abnormal wear,” says Thomas Stacey, Michelin North America’s B2B product category manager – urban and retread.
“Frequent cornering and tight maneuvers cause the tire to scrub with the pavement, also generating heat and potentially leading to abnormal wear or tearing of the tread rubber. Frequent friction with curbs will wear the sidewall rubber down. Crown or sidewall impacts with a curb or a pothole could lead to pinch shocks, causing irreversible damage in the tire or immediate tire failure.”
Matching the application
It makes the choice of the right tire particularly important for the applications.
“Choosing the proper tread design and tire suited for urban use is the first step,” says Darryl Gray, national sales director at Hankook Tire. His company, for example, has a tread design that locks blocks together so they squirm a little less in tight turns. The traction itself is maintained through narrow sipes.
Tire beads can also be designed to better dissipate heat away from the rim, where heat is generated during braking, Stacey adds. “Extra thick rubber in the tire’s sidewall will help extend the casing’s life when put in an application where frequent curb scrubbing is common.”
That extra layer of protection is not always seen at a first glance. Some manufacturers protect the sidewalls with a layer of protruding rubber, but others build the protective layers a little deeper inside the tire, says Walt Weller, Huayi Tire’s senior vice-president – sales and marketing. “It doesn’t protrude out, but it is in that sidewall, and it’s a little bit beefier than a linehaul-type sidewall, and it accommodates the same thing.”
Other vital protection that is more than skin deep comes in the form of steel plies. Some cheaper tires lower costs by incorporating fewer steel belts, but this can sacrifice casing life, Weller says. Such belts serve as a cushion when making contact with potholes.
“In an urban environment, you wouldn’t expect to see a lot of stone drilling,” Weller says, referring to the need to protect casings. “What you might see is a stray rock sitting in the road, or more likely a pothole – and some pretty deep potholes.”
But the tire differences also vary by application. Delivery van tires may not face the same heat as tires in waste management applications because they travel further between starts and stops. Their challenge is in the fight against irregular wear, Gray says.
Enter the focus on the rubber compounds themselves.
“When you use tires for a longhaul application, they do very little in the way of twisting and turning and starting and stopping,” he says. “An urban tire has got to be much tougher, so the recipe for the rubber compounding would be much different.”
“Most urban-use products utilize a varying degree of ‘cut and chip’ or ‘high-scrub’ compounding in their tread, along with sidewall protection technology,” says Clauer.
“Casing durability is also a major factor in meeting these challenges,” he adds, noting how retreading can be a cost-effective option for urban fleets. “Many products are considered ‘disposable’ because it’s not a 295/75R22.5 longhaul tire, however, the same principles of economics apply. Multiple lifecycles equate to lower cost per purchase.”
Pressure and maintenance
Admittedly, urban tires don’t always get the care and maintenance they need.
“A lot of times people will pick an air pressure and say that’s where we’re going to run at,” Gray says. “You have to match the air pressure of whatever you’re using to the load you’re carrying. That’s how you gain the best care, the best handling.”
Steer, drive and trailer tires all carry significantly different loads. One of the bigger challenges, though, is that these vehicles will tend to carry diminishing and varied cargo. A courier van loaded to the roof at the top of a run will be empty when it returns. The reverse is true for waste management vehicles. And a hardware store that hauls skids of paint one day could be moving a load of Styrofoam coolers the next.
“Maintaining the urban application is a little bit more challenging because you are making multiple stops, and you are gradually unloading your cargo over a period of eight hours,” Weller says. “Air pressure maintenance is huge. You can’t average that stuff.”
“For heavy truck tires with steel casings, the optimal tire pressure should always be set based on the heaviest load that will be put on the axle — using tire manufacturer load and inflation tables,” Stacey agrees. For light truck tires, which tend to have textile casings, the correct pressure per axle can be found by referring to an owner’s manual or tire information sticker on the vehicle itself.
But it’s never a matter of set-it-and-forget-it when it comes to establishing tire pressures. These tire experts stress the importance of regularly monitoring pressures to maximize life and minimize downtime.
“There are several best practices that can be used to strengthen the [preventive maintenance] schedule. These include incorporating pressure checks into driver vehicle inspections at the beginning and end of every shift, creating individual alerts based on time or mileage for each vehicle in the fleet, and using a telematics solution to track maintenance needs,” Stacey says.
He also recommends adding tread inspections to the PM checks.
“In some applications certain types of wear, such as faster wear on the drive or steer axle, or heal and toe wear, can be difficult to avoid. Proper tire inflation and tire rotation can delay the onset of abnormal wear and extend the life of the tires.”
But drivers have a role to play as well. Encouraging those at the wheel to avoid harsh acceleration and braking will help to minimize the damaging heat. A little less contact with the curb will also avoid “sidewall scrub and pinch shocks,” Stacey says.
The care even begins before the tires are mounted.
“Proper tire mounting procedures are crucial to getting the most out of your tires. A bead that is not well lubricated or properly seated on a rim will cause the tire to develop abnormal wear and vibrations throughout its life. If tires are mounted in house, ensure that maintenance personnel are trained on and following industry guidelines to mount tires properly and safely,” Stacey says.
Maintenance teams should also be aware that the demands on the tires continue to evolve, especially when it comes to the rollout of battery-electric vehicles.
“They present even more daunting challenges from a design standpoint,” Weller says, referring to the added torque such trucks will deliver to their wheel ends. “They’ll go from zero to 60 or even zero to 40 [miles per hour] in maybe half the time than a typical gas-powered engine.”
That will make tire wear a particularly serious issue, Weller says.
“There are not a lot of electric vehicles out there at the moment. But they’re coming.”