The trucking industry is as diverse as the economy it drives, and tire manufacturers have developed hundreds of different tires for every conceivable application. A good first cut in narrowing down th...
The trucking industry is as diverse as the economy it drives, and tire manufacturers have developed hundreds of different tires for every conceivable application. A good first cut in narrowing down the right choice for the job can be made on manufacturers’ Web sites, which have done excellent jobs of organizing their tires by application – from straight-line coast-to-coast to curb-stomping pick-up and delivery, from steer tire to trailer. But manufacturers are of one voice that wise fleet purchasers should work with trusted tire dealers to make the best choices.
“Sometimes the best tire for a fleet is a highway tire, sometimes a regional. It really requires that the representative know the fleet. I think it is critical that the person responsible for purchasing tires learn about tires and shop around for a dealer in which he can have confidence so he can form a good relationship,” says Ralph Beaveridge, Michelin’s Marketing Manager, Truck Tires. “The penalty for picking the wrong tire can be high. “The reduction in performance can be from 10% to 70%. My best example for a reduction in performance of 70% would be buying highway tires for an urban fleet such as garbage hauler,” says Beaveridge.
Even when spec’ing original equipment tires, having your tire dealer on-board is a good idea. “Fleets do not make mistakes if they work with us originally, but fleets can spec original equipment tires that get 50,000 miles instead of 100,000 miles,” says Al Cohn, Manager of Strategic Initiative with Goodyear Tire. “The truck guy may not understand your application as well as your local tire dealer.”
Tire dealers are well trained, adds Cohn: “We have dealers coming in for three-week training courses. There is training in the field. We have a tremendous training facility in Akron, Ohio.”
Manufacturers list categories of applications, but they are rough guides no one expects will exactly match the real world of varied geography, climate, truck configurations, loads or driving habits.
Michelin calls driving 80,000 to 200,000 miles/year “long haul” or “line haul” and 30,000 to 80,000 miles/year and 300 miles or less operating radius “regional” but the nuances of an application can mean that some line haul tires are appropriate to regional driving, say, for the twists and turns of Maritime highways. “Is he best served by a highway tire? I don’t think so. The guy in British Columbia typically tells me he is doing line haul because he is going over the mountains. But at some point he is going to ask about traction,” says Beaveridge.
Traction is not entirely compatible with the fuel-efficient tires that fleets like to use on line haul service. Fuel-efficient tires for line haul is not a typical choice in Canada, where traction is important for winter, northern and mountain conditions. “Most fuel efficient drive tires have yesterday’s traction. It is harder to get a more fuel-efficient tire for Canadian conditions,” says Beaveridge.
A highway steer/trailer tire suitable for exclusively or nearly-exclusively paved road driving will provide good driving stability and tracking by virtue of a straight “rib” design, is resistant to hydroplaning, runs cool and resists irregular wear, according to Greg Cressman, Yokohama’s Deputy Director of Technical Services. Yet it is not as cut-resistant as a tire designed for any off-road use.
Shoulder grooves were developed to resist irregular wear in line haul applications, but for regional applications a tire with square shoulders is more resistant to twisting and turning. Yet, says Beaveridge, “[it] would suffer in a line haul application because it doesn’t have the stepped shoulders. The stepped shoulder is recessed and when it hits bumps it is harder and absorbs the shocks and resists irregular wear.”
On/off road driving applications can be thought of, percentage-wise, as 80/20 to about 50/50 on and off road driving. But there are several such applications; e.g., forestry, petrochemical, farm application. “In each case it is recommended to spend some time with the sales representative. It is a very specialized area,” cautions Beaveridge.
Move into pure or almost exclusively off road, and Goodyear will talk about “special service” tires: a good eight to ten categories covering everything from construction to dump trucks to coal hauling to logging. Yokohama calls it “off road”. These tires, says Cressman, have “completely different tread compounding to handle off road abrasion, punctures etc, and beefed up construction to handle higher loads/overloads, shock loads.” There are tradeoffs – kilometres to run out and retreadability are factors – but they are tempered by attaining traction and cut resistance.”
Although manufacturers report that fleets are very well informed, they do make mistakes. “Not accounting for small amounts of off road use, 10% or so, and using highway tires instead of on/off road tires is common. In both, cost per mile when the retread results are in [plus] down time, repairs etc, usually proves the point,” says Cressman.
“If a truck changes service vocation, we sometimes see some issues. The best example is regional line haul, where you may have a week in one kind of service and then a week in another service,” says Cohn.
“Fleets can make mistakes based on the headlines they read; for example, ‘20% increase in run out miles.’ Beaveridge says he’s seen fleets that have made hasty decisions on such reports without recognizing the application for which the tire is specifically designed. Another mistake fleets make is ordering the cheapest tire,” says Beaveridge.
Tire selection is all about tradeoffs; e.g., the need for a high-torque tire in a line haul application; the right tire for a north-south run from snowy Quebec to Texas. “Every fleet has to take the pencil to them. Fleets may track three to four trucks and watch them very closely; for example, check miles per thirty-second of an inch of wear. Fleets do not buy tires because they are 50 cents cheaper than another tire. Mileage, traction, how the casing holds up … there are a lot of issues,” says Cohn.
Speed and Inflation
Truck tires are not delicate roses, but neither are they designed to take the punishment some users hand out. Good vehicle maintenance will reduce all sorts of wear phenomena, but any fleet that lets its trucks go faster than their tires’ speed ratings, or that do not maintain proper inflation, are misusing very expensive assets.
In some instances tires that can carry a certain load below 65 mph may no longer be able to carry it over this speed and are now overloaded. This situation can result in premature tire failure and the tire components may separate, according to Bridgestone/Firestone, whose research has concluded that increased speed decreases tire wear performance and casing durability, and increases tire wear and overall tire expenses.
Tire ratings include speed increments from 50 to 75 MPH. Tires running above their speed rating can be easily damaged through overheating. “You should choose tires to meet your usage requirements first, then drive accordingly. Heavy tread tires cannot be expected to be able to be pushed to an unreasonable cruising highway speed,” says Cressman.
Adding incorrect tire pressure to the over-speed mix guarantees that your tires will not age with grace. “The worst scenario is if you are under-inflated, overloaded and running fast. That is not a good thing,” says Cohn.
Unbeknownst to some drivers, bouncing an iron bar off tires doesn’t count as measuring air pressure. “The number one issue is air pressure. Nobody wants to do it,” says Cohn, who adds, as proof of drivers’ distaste for the task, that, “Inflation on the left side of the truck is always better than on the right side (the right side is better in Europe), the outside duals are better than the inside duals. The right rear inside trailer tire is the worst.”
Michelin’s eTire system, introduced last year, which allows operators to check tire pressure without touching the tire, will make it easier to check tire pressure.
“Fleets don’t understand that if you don’
t maintain air pressure, everything bad happens,” says Cohn. “Fuel economy goes down, your regular wear increases, the number of retreads will go down … heat is a tire’s worst enemy. If you are under-inflated by 20% it will cost you 16% in removal miles.
Proper tire selection and maintenance can start to sound like a Bible, but the reward for staying to script is at retread time. The industry in North America is selling 16 to 17 million new and 17 to 18 million retreads a year and 85% of all fleets are said to retread [their tires]. A fleet that takes good care of its tires can expect to get up to eight retreads from a casing, at a cost of one-half to one-third the cost of a new tire.
Fleets have to work through the numbers, such as the relative advantage of selling their casing versus the downtime associated with retreading. According to Bridgestone/ Firestone, some casing damage, such as nail holes, spot repairs in tires and bead repairs can be made and save the casing.
“In almost every case a quality retread will deliver comparable performance to a new tire. The wear per thirty-second of an inch is comparable and the cost is impossible to beat,” says Bandag’s Don Schauer. “All of the products we have introduced since 1996 are application specific; for example, if fuel mileage is your forte, we have a tread product that will do that.”
But make sure you purchase a quality new tire because the case becomes the raw product for the retread, Schauer advises. “Don’t buy something that is cheap. Look at the tire as an asset and manage it. Some of the best fleets in the country have a 4:1 ratio of retreads to new tires. A retread where the casing is properly inspected and you put on a quality retread product, can run as good as a new tire and save a fair bit of money.”
WAITING FOR WIDE BASE TIRES
Canadian departments of transportation are still not comfortable about letting trucks run wide base tires at axle load levels that would allow them to be competitive and therefore economical alternatives to conventional tires.
Wide base tires, which can shave as much as 1000 pounds off a tandem trailer, are said by their manufacturers to improve fuel economy by 5% or more and increase truck stability and driver comfort.
Although researchers at the Virginia Polytechnic Institute and State University concluded that there is no significant difference in damage to road substructure between wide base tires and conventional tires, there remains the question of whether the tires might damage highways’ wearable asphalt layers more than regular tires, according to Michelin’s Ralph Beaveridge.
That question may have been answered at the Universite de Laval though, which completed a study of this issue last fall. According to Transports Quebec’s Gervais Corbin, the study results should be released sometime this month.
VEHICLE MAINTENANCE THAT AFFECTS TIRE LIFE
Too much or too little toe causes steer axle tire scrubbing;
Excessive positive or negative camber may cause smooth wear on the outer or inner half
of the tire. Slightly negative camber in long haul applications reduces irregular
tire wear and allows higher removable mileage;
Insufficient or excessive caster can have a detrimental effect on tire wear;
Non-parallel drive axles cause tire scrubbing, as does a non-zero degree thrust angle (tracking);
Improper toe-out-on-turns causes radial feather wear across the tread area of the tire;
Loose or worn components in steering and suspension systems can cause odd wear, cupping and flat spots;
Brake heat can cause bead damage, unwrapping of the casing from the bead wire.