What is your principal contact with the road, street, or alley? The tires and wheels.

By Paul Hull

Have you ever sprained your ankle? Stubbed your toe on the corner of the bed frame? Had an ingrown toenail? They don't sound like terrible problems—until they are yours. On your vehicles, the wheels and tires are like your feet; they serve you well without complaint, but nothing works well if they are out of shape or injured. To your vehicle, a broken wheel/tire is worse than a broken ankle. It can't do anything. Refuse trucks cannot hobble along the streets.

A most interesting aspect of tires and wheels is that you cannot separate them. A speaker from Bridgestone Firestone asked his audience to imagine going along the street on just the tires, or just the wheels. Either image is ridiculous. "Wheels play an important part in the overall performance of a tire," says Bill Porterfield for Continental General Tire. "Usually, when referencing a ‘giant' tire, it refers to a five-piece wheel comprising a bead seat band, two flanges, a lock ring, and the wheelbase itself. Within the wheelbase there is a valve spud and the valve to access the tire's cavity and fill it with air. Each and every part of this wheel plays an important role in determining whether the tire is capable of carrying a specific load, at a specific speed, for a determined cycle distance. Proper flange height determines whether the lower sidewall and bead area of the tire is supported. Flange height can vary from 1.5 inches to 5.0 inches for Continental radials or general bias product lines. The wheelbase can also be from 8.5 inches to 36 inches wide, depending on the size of the vehicle and the terrain on which it works." Wheels and tires are a serious, technical partnership. In this area of our work, good enough is rarely good enough.

The Doran PressurePro monitoring system can display the pressure of up to 34 tires.

Tires and wheels are inseparable and they should match each other well. The matching can be quite specific, too. Mismatched tires on dual-wheel positions can have the same effect as low inflation or overload. An underinflated tire on a dual assembly will shift its share of the load to its mate. An inflation difference of 15 pounds per square inch could result in the less-inflated tire supporting 500 pounds less than its mate. Matching the diameter of tires is important, too. A difference of a quarter of an inch in diameter may result in the larger tire carrying 600 pounds more than the smaller. You may already be getting the idea that the performance of your wheels and tires does not end at the point of sale to you. If anything, that's when their ability to last begins, and much of the responsibility is yours.

Retreads Rolling Forward

One way in which departments of transportation (DOTs) and other cash-strapped public authorities have been saving money is by purchasing retreads instead of brand-new tires. There is probably more uninformed garbage spoken about retreads than any other product in our sector; it is quite wrong to consider them in the same category as used cars from the lot that Willy Dealer opened (under his 13th change of business name) last week near Wal-Mart. Those rubber alligators you see on the highways are not typical retreads. Too many are newish tires that have never been retreaded--just abused by neglecting the golden rules about tire pressure and matching.

At one state's DOT, the tire budget was halved and performance was not hurt. As retreads become more popular--estimated annual savings in the trucking industry alone exceed $2 billion dollars--the major retread suppliers are investing more and more in research and development. One of the peripheral considerations is that it takes about 22 gallons of oil for a new tire and 7 gallons for the retread of a suitable candidate; that is significant in this time of unwilling oil dependency. The reason for those numbers is that much of the oil is used in the casing, which is reused (i.e., saved) for the retread. In the most recent figures we saw, of the 32.9 million replacement tires purchased by fleets in one year, more than half were retreads.

Here's a thought for budget-conscious managers: It is usually agreed that about 90% of punctures occur in the last 10% of the tread's wear. Would it not be a practical plan to raise the pull point to, say, 5/32 of an inch from the DOT standard of 2/32? You may find doing that would give you more and better casings suitable for retread savings.

Performance Is in the Air

This Michelin tire was designed specifically for waste-handling vehicles.

If there is one aspect of the tire-and-wheel story that is agreed to by everybody involved, it is this: Maintain the correct tire pressure. (This advice comes from wheel makers, too.) The rule applies to all tires, from your private car to refuse trucks to off-road and construction vehicles. "The most important thing is to maintain the correct tire pressure," confirms Roger P. Best, senior field engineer at Bridgestone Firestone. "In addition, you should also keep the vehicle properly serviced while keeping detailed records of the maintenance." The Tire Industry Safety Council has reports that indicate that nearly half of all tires are underinflated. Tires that are underinflated by 10% lose as much as 12% of their tread life; with 20% underinflation, you could lose almost 23%. More than 80% of tire problems begin with low tire pressure.

"Check the tires weekly, bi-weekly at least," advises Roger Clements, a product engineer at Alcoa, manufacturer of wheels for just about every application. "Check them when they're cold." He also encourages users to read the tire charts and to compare them with the wheel charts. "Good matching of wheels and tires comes from load and pressure," adds Dave Walters, manager of warranty and field service at Alcoa. "And keep that valve cap on! Alcoa is now offering air-through, double-seal caps for their wheels." Metal valves, report both Clements and Walters, work better than plastic. Asked if the strength was in the wheels or the tires, both agreed with everybody else: The strength is in the tires and wheels together.

Getting down to check tire pressure may be neglected because it seems a tedious chore. Consider this solution, announced earlier this year: Doran Manufacturing offers the Doran PressurePro Tire Pressure Monitoring System. It continuously monitors pressure of all vehicle tires and displays them in a digital readout in the vehicle's cab. The pressure of up to 34 tires is shown, allowing the driver to monitor leaks and schedule repairs or replacement without breakdowns or downtime caused by unexpected deflation. Low-pressure conditions are signaled to the driver both visually and audibly. Doran PressurePro has duplicate signals to minimize the effects of electronic interference and weather (and other trucks). It has been successful for dump trucks, specialty vehicles, service trucks, and tractor-trailers, as well as for construction equipment like rubber-tired excavators and loaders. For installation, sensors replace the valve caps, the monitor is mounted on the dash, and the system is hooked up to the standard two-wire power supply.

Are there any shortcuts to keeping that tire in its best condition? There are some obvious comments, but they bear repeating. If wheel maintenance is necessary, deflate the tire first. That is also recommended when you change dual-mounted positions because the outboard tire may be holding damaged rim components in place. You wouldn't weld anything on an inflated tire, would you? Don't even think of it. If the wheel has any obviously worn or rusted components, replace them, too. When you put on a new tire, it's a good idea to replace the valve and spuds. Check your air gauges if they have been dropped or abused. Check them against a master gauge and replace them if necessary, because a correct tire pressure according to an incorrect gauge has no accuracy.

Some of the performance of wheels and tires depends on the driver's conduct. Keep a record of your tires and wheels. You may discover that one operator is harsher than another, or that one is much better than anybody else. Find out why. Start with the positive and determine why your best driver is so good. It could be that he has better tires on his vehicle, or it could be that his driving habits are kinder to the vehicle's feet. His curb approach may be smoother, without slowing him down, or his starting and stopping procedures at each pickup may tell you why his tire history is better than others. In this age when vehicle control is simple and easy, all operators should be taking advantage of new technologies introduced by vehicle manufacturers.

Designed Specifically for Waste Vehicles

Michelin Americas Truck Tires announced earlier this year that it was introducing the ZXU S and the X One XZU S tires. Just another model, just another group of numbers and letters? No. These tires were designed specifically for the use of vehicles in the waste industry. "Michelin has been designing and supplying tires for waste-handling trucks for many years," observes Michael Burroughes, product portfolio manager for Michelin Americas Truck Tires. "These are the first tires we have designed specifically for vehicles that collect refuse and haul it to transfer stations and landfills. We believe they are the first and only tires designed and produced by any tire company solely for waste vehicles."

The basic XZU tire is an all-wheel-position radial for urban operations where frequent stopping and starting are the normal operation pattern. Sanitation trucks, transit buses, and delivery vehicles would benefit from this tire design. A thick undertread with regrooving depth indicators permits efficient regrooving for original tread life, while deep, wide circumferential grooves and dull-depth sipes will provide excellent traction for the life of the tire. Everybody knows one of the most common problems for urban vehicles: curb damage. On this tire there are built-up sidewall protectors against curb damage, and the sidewall wear indicators let the user rotate tires in a timely fashion for long casing life and enhanced retreadability.

Many municipal refuse trucks include alleys in their routes.

The Dura-Flange wheel was designed for heavy, shift-prone loads.

The Michelin XZU S tire is available in the size that has become a virtual standard for the waste-collection industry: 315/80R22.5 load range L. "We see an improvement in tread wear that ranges from 10% to 40%, depending on the vehicle configuration and the particular application," notes Burroughes. "It has an increased maximum speed capability of 65 miles per hour, to help improve productivity for waste collectors. This higher speed capability was made possible by the use of coextruded tread compounds that feature a high scrub-resistant compound developed specifically for urban service, such as waste vehicles. There is a profiled and cooler second ayer of tread rubber underneath. In this design, dual compounding lowers the operating temperatures in the tread area, with no compromise on performance or durability." The X One XZU S mentioned should be available in early 2005, offering an increased load capacity of 11,700 pounds per tire.

The BRM and BDM tires from Bandag are specifically for waste-handling and construction equipment. In tests with Waste Industries Inc., the BRM retread tire showed it would run for 60 working days, as opposed to the current 45 days for tires in the same wheel positions. "That's significant," observes David Peck, fleet manager for Waste Industries, which is based in Raleigh, NC. "It means that each truck equipped with Bandag's BRM will need one less set of drive tires each year. The savings are not only in the costs for tires but in the additional uptime for the vehicle and a reduction in maintenance time." Waste Industries has 1,200 vehicles, with about 40 service locations in the Southeast. Bandag produces tires for the three biggest waste-management companies and for thousands of municipalities.

In recent years, owners of refuse vehicles and transfer trucks—about 80% are private and 20% are public—have analyzed their needs and prepared specifications according to those needs. Tires and wheels rank just behind personnel and fuel in costs, due mostly to the stop-and-go nature of their work, so there has been extensive research into new designs and materials to make them capable of meeting those daily challenges--on the streets or off-road. Some readers may be amazed by the testing facilities that manufacturers like Michelin, Continental General, and Bridgestone Firestone have developed and constantly improved. They have also used job-site simulation, footprint analysis, and X-rays in their efforts to bring the product to your vehicles. By using three-dimensional imaging, engineers can build a tire digitally and then treat it like a real tire, watching its reaction to external forces. They can even ascertain and improve the performance and tread wear--before the tire even exists. No wonder tire manufacturers plead with their customers to do the simple job of maintaining the correct pressure!

Air Substitutes

Nothing stops your happy travel as quickly as a flat tire. There are certain job sites where punctures are more likely than others, and engineers have been trying to come up with a method to prevent the tire's deflation if it is struck by a sharp object. A relative newcomer to this aspect has been Arnco, which produces SuperFlex, a soft-fill polyurethane material. It has been used mostly for off-road tires, and an increasing number of equipment manufacturers are approving its use for their vehicles and machines. One case history comes from the Marion County Landfill in Florida, where the fill was used in garbage rolloff container trucks. There had been excessive downtime and increasing costs for service and repair while the trucks used standard air-filled tires. Before deciding to use the flat-proofing fill, the landfill conducted tests. For one truck the rear axle tires were filled with SuperFlex, while another truck's tires used standard air. The filled tires had less tread wear and showed more even wear than the air-filled tires (and there was no adverse effect on the braking system). The truck tires at this landfill hold about 250 pounds of fill each. Each truck has two rear axles, with eight rear tires. The steer tires were not filled.

There were no flats, no blowout hazards, and no costly downtime or tire repairs. The patented polyurethane liquid is pumped into the tire by an Arnco certified dealer; it cures into a soft rubber-like material that fills the tire. It works in any tire with a sound casing and its shock-absorbing properties offer a superior "softness" of 8 on the durometer. At the Marion County Landfill, 28 trucks have their tires filled with SuperFlex. They carry weights of 40,000 to 60,000 pounds per load. There has been no downtime due to flat tires. Arnco's traditional customers have been owners of aircraft and construction and mining equipment. Now it seems that their patented fill for tires is conquering the municipal market, too.

Radial Versus Bias?

It's not really a battle. Radial tires and bias tires are designed differently and each style has proved its merit in certain conditions. They are constructed in two entirely different procedures. The bias tire gets its strength from nylon cord placed around a bronze-coated high-tensile bead bundle. The plies are layered at a bias angle around a certain number of bead bundles, varying usually from two to three. This combination of plies and bead bundles determines the load-carrying capacity of the tire when it is properly inflated. The bead bundles become the major component of the bead base that anchors the tire to the rim.

Radial tires are built with one bead bundle. Instead of those multiple "bias" plies, there is a single layer of steel cord wire. The wire runs from bead to bead laterally to the direction motion. That's why the design is called radial. A component difference between the two is that a radial tire is built with steel belts while a bias tire (in most designs) is built with breakers. "Our radials—have from two to five steel belts," notes Bill Porterfield of Continental. "Steel belts are designed to stabilize the tread while increasing the cut resistance of the tire. The steel belts also transfer torque forces to the radial ply and restrict tire growth to prevent cutting, cut growth, and cracking. In our bias tires, the breakers provide a similar function while protecting the cord body. The breakers are made of nylon, our own Aralon (nylon and aramid combination), and steel wire."

One recommended method for deciding which tires are better for your applications is to work out the cost per hour. The initial cost of a radial tire is higher than that of a bias tire. Among the established benefits for bias tires are vehicle steadiness, sidewall cut resistance, reparability, and self-cleaning capabilities. Radials offer heat resistance, floatation, and better traction. The resistance to wear and fuel economy for any tire will vary according to the operator, the terrain of the site (paved streets versus alleys or haul roads to the landfill), and the efficiency of the maintenance program. And, let's say it once more, the air pressure.

Supporting the Tires

Representatives of wheel and tire manufacturing companies have told us that you should not separate the tire from the wheel, literally and metaphorically. They work together. It seems, however, that we think more about tires than wheels, as if all wheels were the same. The main differences we observe are that there are steel wheels and aluminum wheels. That is something of an insult to the engineers who research and design new wheels.

Porosity is something that wheel manufacturers worry about. They don't want it and neither do you. If the design of the wheel encourages porosity, then the air will escape slowly but surely and lower the efficiency of the tire/wheel assembly. "Forged aluminum wheels in one piece are the strongest," asserts Roger Clements of Alcoa. "Cast aluminum wheels are painted against porosity," adds Dave Walters from Alcoa. "Steel wheels with several welds can cause porosity." When choosing wheels for your vehicles, Clements advises that you pay great attention to load ratings, and then that you match load and pressure. But why aluminum wheels? "Basically, aluminum wheels have less weight [for an increased payload and greater fuel economy]. They offer better heat dissipation for extended tire and brake life." He adds that a lighter wheel on a heavier axle can cause cracks. Both stress the importance of consulting with wheel experts and studying the charts. There is a natural tendency in most of us to get a little more than we should out of engines, wheels, and tires, but it is not a good practice and could lead to vehicle damage costing much more than the mismatched wheel/tire assembly.

An example of wheel development is the Dura-Flange from Alcoa, an aluminum wheel that was developed specifically for vehicles whose loads are heavy and inclined to shift. That shifting causes the tire walls to run against the wheel rims. Extensive field-testing has demonstrated that the Dura-Flange can cut rim flange wear dramatically.

Local Habits

"Most of the garbage-truck tires we receive have several, as many as eight, holes in them," notes Jack Freebury, who works for a tire repair shop in Montana. The shop works with both city and private refuse vehicles. "The city can repair tires, to a certain extent. They plug them. That means they don't have to take the tire off the vehicle; saves them time. Not sure if it saves them money. When the tire has enough plugged holes in it, they bring it in here for patching and real repair." Most of the holes are caused by nails and other objects on the ground between the city streets and the landfill, rather than from objects on the streets themselves. Some houses have their garbage containers in alleys, which are always more likely to have nails and sharp objects. An interesting observation made by Freebury was that almost all the holes were in rear tires. It is as if the front tires pick up sharp objects and hurl them backward to be caught by the rear tires. He has noticed the same phenomenon with gooseneck trailers. "Something else I've noticed, too often, is that the tires in dual groups are seldom matched for tire pressure," adds Freebury. "That's asking for trouble." As in many situations that involve inspections and maintenance of vehicles and equipment, the principal problem appears to be not in the ability of employees to do the inspections but in making the daily, albeit tedious, effort to do them as scheduled.

Mark Gray, an experienced driver of a garbage truck in the same community as Freebury, confirms that the greatest hazards come between city streets and the landfill. He says that the community is too small to support a transfer station. Bigger communities use transfer stations to protect the tires of their vehicles. Only a small number of trucks go from the transfer station to the landfill. Reports say this has cut down dramatically on the number of vehicles affected by the off-road part of their routes. "We use retreads on our trucks and they have served us well," notes Gray. "They last well and they don't collect nails any more than any other tires. My own experience is that a nail can penetrate any tire, whatever type it is."

One way to reduce tire damage at your landfill would be to check the frequency of cleaning of the deck area from which trucks discharge their loads. "The deck often has many leftover items from dumping that the next vehicle in line must travel over to dump," observes John Vastine, a Bandag fleet development manager. "The loader operators at these landfills could be a significant aid to fleets by clearing that deck two or three times per working shift. Studies have shown this practice to be successful in reducing landfill tire failures."

Paul Hull writes on construction and environmental topics for several international magazines.

MSW - November/December 2004