Built to Last: Smart Lifecycle Cost Control Can Help Fleets Squeeze Every Last Mile Out of Every Casing - Tire Review Magazine

Built to Last: Smart Lifecycle Cost Control Can Help Fleets Squeeze Every Last Mile Out of Every Casing

Here’s a bulletin for fleet maintenance managers responsible for extending tire casing life: If you start a serious tire inflation program today, you will enjoy a 10% improvement in tire mileage expectations tomorrow.

That’s only the beginning. If you add a proper tire rotation program, daily calibration of your tire pressure gauges, an alignment program and match up your duals to within 1/4-inch, you can expect the life span of your tire casings to improve by 30%.

Of course, you can’t control all of your costs. Diesel fuel – pushing $3 a gallon – is just one example. So, your time is best spent focusing on the costs you can control – like tires. The industry average for roadside downtime is 2.5 hours, and the number-one reason for that downtime is tires. With 18 tires on one vehicle, the odds are stacked against you.

So, how can you improve the odds and, therefore, your lifecycle costs? For starters, underinflation still looms as the number-one reason for premature removal of a tire from service. Even though the tire industry has been preaching about underinflated tires for decades, the message falls woefully short.

That’s too bad because underinflated tires mean nothing but trouble. Fuel economy goes down. Casing life drops dramatically. Removal miles, for the original tread and retreads, also go down. If your fleet runs tires that are 20% underinflated – 20 psi on a 100-psi-recommended pressure – for one year, expect removal mileage to drop 12% to 16%.

Even though most fleets know all of this, many maintenance programs still fall short. Inflation checks are an unpleasant, time-consuming task, to be sure. And, a yard packed with tractors and trailers is uninviting for even the greenest employee. Regularly scheduled checks multiply the problem.

But, at more than $300 per new radial and $150 per retread, tires remain a major investment for any fleet. With today’s rising raw materials costs and resulting price increases – not to mention the high price of diesel – wringing every mile out of every tire should be a priority.

Inflation and Tire Life

Al Cohn, commercial truck tire technical marketing manager for Goodyear, says that most fleets don’t think about the consequences of underinflated tires. “These tires quickly develop a larger footprint than a properly inflated tire. That big footprint will ‘suck up’ tire-killing objects on the road like a vacuum cleaner. You can also expect significant irregular wear. If our job is to protect the original casing, we can, and must, do a lot better.

“Let’s say that you’ve spec’d your new tires to run for 150,000 miles before removal,” says Cohn. “If you run those tires 10% underinflated, you’ll be down 10% in projected tire miles. That’s 15,000 miles right there. Not good. And, if you run your tires at 20% underinflation, you’ll be down in expected tread life about 12% or 14%,” Cohn says.

In terms of retreadability, Cohn says running 30% underinflated drains 30% of the life out of a good radial casing.

Another common issue, says Cohn, rests with how much air to put in a tire, when to put it in and at what ambient temperature. “Job one is to do your best to fill tires in a controlled temperature situation,” says Cohn. “Tiremakers like to talk about 100 psi at 60ºF ambient temperature as an ideal starting point.

“If you fill a tire to 100 psi at 60ºF outdoors and wait a day before moving that tire, look at what can happen overnight. Let’s say the next day, temperature jumps to 100ºF outside – the inflation pressure will jump to 110 psi just by sitting there.

“The reverse is also true. If it’s 20ºF the next day – which happens – your tire gauge will show there is only 90 psi in the tire,” Cohn claims.

The lesson is basic, says Cohn: It’s important that inflation pressures are checked regularly.

Gauging Accuracy

Taking that a step further, Cohn says regularly calibrating tire gauges is a must. “But here’s the problem,” he says. “Let’s say the fleet shop has 10 guys, each with his own gauge. He’s got it taped up and contoured to his hand; it belongs to him. He may have had it for years. Now, if you ask all 10 guys to check the pressure in a tire that we know has been filled to 100 psi, guess what? You get 10 different readings, and some of them could be 12 psi off.”

Ideally, inflation gauges should be recalibrated daily. “This is especially critical for P&D fleets where you’re hitting curbs and running over a lot of debris,” Cohn says.

Dual-ing ODs

Another big contributor to lifecycle costs is tied directly to matching up duals. Mismatching duals happens often, and the taller tire – the one for the larger outside diameter – is forced to carry more of the load. As a result, that tire will wear out faster and more unevenly than its neighbor, not to mention the additional heat buildup the tire will suffer.

And, the smaller-diameter dual next to it is being scrubbed and dragged along as it tries to make a revolution that matches up with its larger OD running mate. Both tires are going to miss their projected lifecycle costs by a lot.

“This is a bad situation,” says Cohn. “Make sure your duals are never more than 1/4-inch diameter different in OD. Some suggest 1/2-inch, but I say 1/4-inch.”

Million-Mile Casing?

“We’re all in the chase for the million-mile casing,” says Guy Walenga, commercial tire engineering manager for Bridgestone/Firestone North American Tire (BFNAT), “but to get there, we must protect the original casing.”

Walenga says he’s seen quite a few million-mile casings in his time, but most fleets won’t see such spectacular service. Whether your goal is a million miles or maximum lifecycle, how you get to that point depends on application and time spent in service.

“Secret number one is to make sure the new tires you buy are designed for retreadability,” he says. “The second ‘open secret’ is to place that new casing in line-haul service, on the steer axle, where it will rack up lots of miles very quickly. When you reach your pre-set removal miles for that casing, retread it, move it back to the drive axle and keep it in line-haul service. Once again, you are going to pile up a lot of miles very quickly.

“Since time and distance traveled are key to attaining the million-mile goal, once you place that casing on a trailer, it’s going to spend a lot of time sitting around,” says Walenga. “The casing ages, and the miles drop off.”

Service Essentials

Alignment and rotation are probably the two most important service functions in terms of preserving tire life and keeping costs down.

Cohn says the number-one reason for regular truck alignments is to keep fleet drivers happy. “The second reason for aligning a new truck is tire mileage. When a fleet buys a new power unit, that vehicle will create a ‘set’ in its new tires, even if it has been factory aligned. Our advice is to check the alignment within 30,000 miles or 90 days. Check all the angles.”

Interestingly, Cohn says one of the biggest problems facing fleet alignment today is the trailer. “Most fleets don’t own their own trailers. So, they don’t want to pay to have them aligned,” Cohn says. But an unserviced trailer will wiggle-waggle down the road, negating the work that’s been done on the tractor-tire program.

“You have to be running in a straight line to pick up that 30% gain in lifecycle cost,” adds Cohn.

Another thing fleets talk about is tire rotation. Tires tend to wear more in certain positions, such as the front vs. the rear. Tires on tandem drive axles wear at different rates, depending on whether they are on the front or rear drive axle.

Walenga notes that many fleets report the driver’s side steer tire tends to wear faster than the right side steer, not unlike passenger vehicles. Solution? If the driver’s side steer has 4/32nds or less remaining tread depth compared to the right-side steer, consider a left-to-right rotation.

Failing to rotate tires where there is a high discrepancy in wear between positions will lead to too-early scrapping. “Some fleets don’t rotate because of the extra labor involved,” says Cohn. “But if their trucks are in for service anyway or a regular PM check, there’s enough value in tread and casing life to make tire rotation worthwhile.”

Some fleets are using rib-type tires all the way around. What seems to work well is to run these tires for about 30,000 miles, then swap the steer pair with those on the left rear tandem. If an additional rotation is needed, the steers (previously the drives) can be swapped with the tires on the right rear tandem. For convenience, repaired tires can be placed on the front tandem.

Even so, the most common type of rotation on the drive axle continues to be cross rotation, in which tires are swapped from one side to another, and those on tandems are also swapped between axles.

As far as removal from service altogether, DOT standards for fleet removal miles are 4/32nds for steer axle tires and 2/32nds for both drive and trailer axle tires. But, Bandag’s Don Schauer doesn’t think fleets should wait that long. “We recommend tire removals at 4 to 5/32nds. This way, fleets can preserve casing life and experience fewer casing injuries.”

Because many fleets are using very deep tread drive axle tires – 30/32nds or 32/32nds – they should consider moving a tire that’s approaching its removal mile mark back to the trailer. Then, when that tire is ready for retreading, move it back to the drive axle or leave it on the trailer.

New Way of Thinking

Somewhat new is the business of concentrating on a casing’s useful life “one 32nd at a time.”

On average, “a casing in line-haul service should realize 15,000 miles per 32nd of tread depth,” says Cohn. “Every fleet is different, every driver is different, and every load is different, so it’s nearly impossible to make hard and fast lifecycle pronouncements.”

To monitor tire lifecycle costs, a fleet or servicing dealer should purchase tire-tracking software, available from most tire suppliers. These programs allow a dealer to track nearly every aspect of a tire’s life, from initial order through every retreading on to the scrap pile – and the resulting costs along the way.

Some fleets get seriously scientific when calculating costs and even consider vehicle duty cycle, road surfaces, climates and drivers.

Certainly, if it were left up to accountants, fleets would buy the least expensive trucks and ride on the cheapest tires. But, real-world financial performance cannot be left to the low bidder.

Having detailed lifecycle cost stats usually proves the accountants wrong. If an inexpensive tire comes with an early removal time and just one retread, it costs a great deal more than a more expensive tire with greater initial removal mileage that allows for multiple retreads. That’s why fleet operations people know that a less expensive tire may not be the best buy.

Extending tire lifecycle cost is imperative to fleets that wish to remain competitive in their pricing while delivering freight on time.

At the end of the day, the benefit is really not hard to understand. Putting it into action? Well, that’s another matter.

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