August 4, 2014 by Minuteman Trucks
HDT’s editors combed their own knowledge from years covering the trucking industry, and asked readers, suppliers, and other experts for their tips on ways to save money on fuel.
Part Three: Tires
- Buy fuel-efficient tires: Getting the right tire at the right wheel position can improve fuel economy by several percentage points. About 13% of each gallon of fuel consumed goes solely to overcoming rolling resistance. That can vary by the load on the tire, the tread pattern and of course, inflation pressure. “The relationship between rolling resistance and fuel consumption is about 8:1,” says Rick Phillips, senior director of sales, commercial and OTR products at Yokohama Tire. “An 8% reduction in tire rolling resistance will result in a 1% savings in fuel consumption.” Various wheel positions have different impacts on fuel economy. “On a tractor-trailer combination, the steer tires contribute 15-20% to fuel economy, drive tires 30-40% and trailer tires about 40-50%,” says William Estupinan, vice president of technical service for Giti Tire USA. “The first priority for a fleet interested in saving a significant amount of money is to start moving toward fuel-efficient tires for the trailer axles.” A tight rib pattern, thinner tread — 12/32- to 20/32-inch of tread depth — and advanced compounding make today’s trailer tires very fuel-efficient. With drive tires, traction and durability are higher on the list of priorities. But traction hasn’t really suffered in a significant way in the quest for lower rolling resistance, manufacturers say.
- Wide-base singles, Carry a spare: One of the big concerns with wide-base tires was the inability to “limp” to the nearest repair facility if you had a flat, as you could with a set of duals. Mesilla Valley Transportation designed a bracket to carry a spare, and bought the tires in quantity so they could get them at a lower cost. ATDynamics offers such a mount, called the SuperSpare.
- Fuel-efficient duals or wide-base singles? Some fleets find wide-base single tires work best for improved fuel efficiency, while others prefer fuel-efficient duals. The basic advantage claimed by promoters of single tires is fewer sidewalls. Eliminating two sidewalls and bead areas by switching to wide-base singles can cut flex-related rolling resistance nearly in half. There are weight savings as well, something in the order of 800 pounds over four axles. For low-rolling-resistance tires, various tire models usually claim a certain percentage of savings (which some say you can discount by 50%). If a tire claims a 10% reduction in rolling resistance, equipping the entire truck with such tires would net you a 1% reduction in fuel consumption. But you’re going to give up some mileage with a thinner tread. Al Cohn, director of new market development and engineering support for Pressure Systems International (makers of the Meritor Tire Inflation System), estimates the cost per mile for a typical non-fuel-efficient tire is $0.011, or 1.1 cents, while a typical fuel-efficient tire is $0.013, or 1.3 cents. A 1% savings in fuel consumption, going from 6.0 mpg to 6.06 mpg, would save $660 at $4 per gallon over 100,000 miles. According to Cohn, giving up about 10% in the tread mileage for the fuel-efficient dual tires would cost about $200 per year, yielding a net savings of about $460 per year per truck.
- Don’t scrub away your savings: You’ve heard the expression, “It’s like herding cats.” It’s like that with tires when your alignment is out of whack. With all those wheels heading in different directions, it’s unlikely you’re getting the best fuel economy. Bridgestone’s Guy Walenga says when a wheel is misaligned, it’s like dragging it sideways across the pavement. “If you have a 2-inch misalignment between steer and drive tires on tractor with a 181-inch wheelbase, it would be like scrubbing the tires across the pavement for about 60 feet for every mile you drove,” he says. “Increasing the scale for dramatic effect, over a year, that would amount to dragging the tires sideways for about 1,100 miles. Not only is that going to produce tire wear, it saps fuel economy, too. It takes a lot of energy to drag a tire sideways, and the energy comes right from your fuel tank.” Justin Gonzalez, heavy-duty marketing manager at Hunter Engineering, says his company is starting to get inquiries from fleets that are already doing everything else to reduce fuel costs. “If it’s preventing tire wear, it’s saving fuel. Any forces that are scrubbing rubber off of tires are also increasing resistance to forward movement. That hurts fuel economy.” Checking trailer and drive axle alignment can be as simple as using a measuring tape, while steering geometry can be more complicated. Machines from Hunter, Bee Line and others are one solution. Portable laser devices from MD Alignment, E-Z Line and others offer a do-it-yourself solution.
- Find your ideal tire pressure: Many fleets choose 100 psi as an arbitrary but safe pressure, but it might not be ideal. Yokohama’s Phillips suggests fleets should be running dual tires in a fully loaded tandem axle (34,000 pounds) at 80 psi, not 100. “I’ve seen very little evidence of quantifiable fuel economy gains from running at 100 psi rather than 80, but I can show lots of tires that were scrapped prematurely because of irregular wear arising from overinflation.” There are several variables that fleets consider when setting a standardized pressure, including ambient temperature changes, vehicle speed, and of course, load, explains Donn Kramer, director of product marketing innovation, Goodyear Commercial Tire Systems. “A tire with an initial cold inflation pressure of 100 psi at 60 degrees Fahrenheit ambient temperature will experience a 2-psi change for every 10-degree F change in ambient temperature. And fleets operating at 66 to 70 mph should increase their tires’ cold inflation pressure by 5 psi.” Find the ideal pressure for your fleet based on loaded conditions, and use all the help you can get to maintain it.
- Inflate your tires, not your fuel bill: Under-inflation kills not only tires, but also fuel economy. A tire underinflated by 10% can result in 20% increase in rolling resistance, and a corresponding drop in fuel economy. It’s hard to imagine giving up 2-4% in fuel efficiency to something as simple as maintaining correct inflation pressure. Improper inflation bites you in two ways: It reduces the ability of the tire sidewall to support the load on the tire, which increases the degree to which the sidewall will flex; and it changes the footprint or contact patch of the tire. “It is not the tire, but the air inside it that supports the load,” says Guy Walenga, Bridgestone director of engineering, commercial products and technologies. “And it is the air inside the casing that keeps that casing the right shape.”
- Stretch (and record tire pressure regularly): Drivers are encouraged to stretch their muscles before a trip to reduce injuries. They also must check tire pressure. Combine the two activities, suggests Jeff Baer of LinkeDrive, which makes the PedalCoach in-cab driver fuel economy coaching system. “Reaching low to actually check the pressure is a great opportunity to perform back and lower body stretches,” he says. “Checking tire pressure is the first step towards maintaining it, but recording it and maintaining this information can show easily where it is not being checked, and thus the opportunity to improve. Keeping a record of both to feed a participation bonus can reap big rewards.”
- Make it easy for drivers to air up their tires: “I love it when fleets have air at the fuel islands and none of the hoses work,” says driver David Fanning from El Paso, Texas. “These are the same people so concerned about saving fuel but won’t maintain the fuel islands.” That’s why New Jersey-based NFI has put in air hoses at all its facilities and keeps them working. Some conscientious drivers have carried an air hose that you can plug into a wet tank or a gladhand to pump air when a tire needs it. However, Fanning notes that idle shutdown timers may make this impractical.
- Use automatic tire monitoring and inflation systems: A U.S. Department of Transportation field test of automatic tire inflation and tire pressure monitoring systems found a 1.4% reduction in fuel consumption for fleets using the systems. John Morgan, product manager for Meritor Tire Inflation Systems by PSI, notes that “The final bit of proof is that the fleets in the trial are still using the systems, and have equipped more vehicles in their fleets since the study wrapped up in 2010.” Jim Samocki, general manager at Doran says, “When we first install a TPMS system on a fleet, they can’t believe what they see. Tire pressures are usually all over the map. That’s when the impact of improper inflation starts to sink in. They’re thinking of tire wear and damage, of course, but fuel economy is never far behind.” Other systems available include Advantage PressurePro TPMS, Airgo ATIS, Aperia Technologies’ Halo ATIS, Bendix SmarTire TPMS, Hendrickson TireMaax ATIS, Stemco’s Aeris ATIS, TireStamp TPMS, and others. Tire pressure monitoring systems are also increasingly offering the ability to use telematics to remotely notify fleet management of under-inflated tires in real time, in addition to warning drivers.
- Don’t pull tires too early: Tires that can be run out to the minimum acceptable tread depth, without being pulled prematurely due to irregular wear, “contribute greatly to reducing a vehicle’s fuel consumption, since tires with reduced tread depth roll more freely,” notes Bill Sweatman, president and CEO of Marangoni Tread N.A. Manufacturer studies show that a tire that is 80% worn is something like 6.5% more fuel-efficient than a new tire, due to the thinner tread. Unfortunately, tires pulled prematurely due to irregular or uneven wear won’t see their best days from a fuel efficiency perspective.
- Retreading: Retreading offers the opportunity to spec your tread pattern and compound from what is emerging as a boutique offering of fuel-efficient treads. In June 2012, EPA created a SmartWay designation for retreaded tires, allowing the manufacturers to develop specific treads, with various patterns and compounds similar to their original offerings. Since then, more than 40 tread options for tractors and trailers have emerged from industry suppliers such as Bandag, Continental, Michelin, Marangoni, and others. The beauty of this is you can now apply a top-of-the-line fuel efficient tread to any suitable casing, expanding your options for a low-rolling-resistance spec.
- Get ready for ATIS for drive axles: While automatic tire inflation systems are seen only on trailers, a few manufacturers are readying products for drive axles, too. It’s more complicated getting air into the hub when the axle shaft’s in in the way, but it’s coming. A Meritor-PSI system is said to be in field tests, as is a system from Airgo. But there’s one system available now from Aperia Technologies that uses an internal pump rather than air lines to deliver up to 120 psi to the drive tires. “The system operates on a similar principle to a self-winding watch,” says Josh Carter, CEO and co-founder of Aperia Technologies, which makes the Halo system. “It uses a wheel’s rotational motion to pump and maintain optimal tire pressure. It does not require any connection to a compressor, and can be installed in about 10 minutes per wheel end.”
- Get in their face: NFI, a New Jersey-based fleet, is putting automatic tire inflation systems on its trailers, but that still leaves the tractors, as well as older trailers that haven’t been converted, says Bill Bliem, senior vice president of fleet services. “We have put on a big push this year with our drivers on pretrip inspections, and part of that pretrip is checking the air pressure – not kicking the tires or hitting them with a club,” he says. The solution? Clips mounted on the side of the driver’s seat so the air pressure gauge is staring them in the face when they open the door, a not-so-subtle reminder of what they’re supposed to do.
- Keep tires and wheels balanced: Because tires are part of a rotating mass that revolves around the axle spindle, the entire package — hub, brake drum or rotor, wheel, and tire — can affect fuel efficiency. When a tire is not balanced, it vibrates (roughly 10 times a second at 66 mph), causing irregular wear (which contributes to tires being pulled before they wear down to their most fuel-efficient tread thickness) and wasting energy meant to propel the truck forward. John Tak, director of marketing and product development at IMI, which offers the Equal internal balancing product, says an out-of-balance tire will wear more quickly and develop uneven wear patterns. “If you want to get optimum mileage from the tread, and therefore optimum fuel efficiency from the tire in the last third of its life, balancing is necessary,” he says. “Balancing isn’t expensive at all compared to the fuel-saving benefits.” There’s also evidence that a balanced tire and wheel, even in its early or mid stage of life, can improve fuel economy. SAE Type II fuel economy testing done in 2008 for Counteract Balancing Beads at a test track in Indiana, revealed that properly balanced wheels produced a 2.2% improvement in fuel economy. Coley Wolkoff, Couteract national accounts manager, notes that in these days of four-dollar-diesel, 2.2% is more significant than it may sound. Of course, traditional balancing methods are effective as well, for most of the same reasons. “Balancing machines help detect radial and lateral run-out as well as non-concentric mounting and even improper matching of the high and low spots on the tire and the wheel,” says Jason Gonzalez, heavy duty marketing manager at Hunter Engineering. “If you let the machine do its job, you’ll know you have a perfectly mounted and balanced tire and wheel when you’re done that will minimize rolling resistance due to non-true rotation.”
Check back frequently for the next 6 installments! Source HDT truckinginfo.com.