Despite Mother Nature's frowning on Nashville, Tenn., in February, the American Truck-ing Associations' Technology & Maintenance Council's (TMC) 2015 Annual Meeting and Transportation Technology Exhibition was held there. Unfortunately the event was held the same week a winter storm and polar vortex descended upon the city, freezing it over and closing the airport, interstates and roads around and through the city. For those of us who battled the elements to be there, the fight was well worth it. Many new products and technologies were introduced on the 370,000-sq.-ft. exhibit show floor. And there were many sessions of great interest to the more than 3,000 fleet maintenance managers, tire dealers, truck dealers, truck stop operators and trucking industry supplier members who attended. A tech session presented by the Tire & Wheel Study Group was entitled, “The Facts Behind Low-Rolling-Resistance Tires.” While you probably know all about these tires, fleet users' interest in them has grown considerably in the last few years since they were introduced in the early 1980s. Back then low-rolling-resistance tires were reported to save 3-4 percent in fuel and were about 15-percent more expensive than regular truck tires. The drawback of low-rolling-resistance tires at that time was that with the raw materials used to build tires then, tread life was significantly reduced in order to maintain the traction needed to operate safely while also reducing roll-ing resistance. Since diesel fuel was still under $1.50 per gallon, the fuel savings did not pay for the loss in tread mileage and increased purchase cost. As a result, sales of low-roll-ing-resistance tires were sparse until 2008 when diesel soared to $4.74/gallon and SmartWay and the California Air Resources Board (CARB) put pressure on fleets to buy fuel-efficient tires. Today, due to new developments in tire production and raw materials, the tradeoffs in traction and tread mileage to produce low-rolling-resistance tires are much smaller. In addition the cost premium for these tires is much less. As a result of these developments, the high cost of diesel and government pressures, low-rolling-resistance tires now comprise 35-40 percent of the medium truck tire market while wide-base tires make up about 5 percent. So naturally there was considerable interest in a program on low-rolling-resistance tires at TMC. Featured in this program were: Michelin North America Inc.'s Phil Arnold, who provided a background of what constitutes a low-rolling-resistance tire and how these tires are made; Dustin Stricker, maintenance manager with R.E. West Transportation, who described a test he ran with wide-base tires to determine their fuel economy; Madhura Rajapakshe with Smithers Rapra, who explained lab testing for rolling resistance and correlated his lab results with Mr. Stricker's field tests; and I provided the results from a survey TMC conducted on low-rolling-resistance tires. In the past several months many fleets that are members of the TMC, as well as fleets in other organizations within the American Trucking Associations (ATA), have been concerned about the loss of tread mileage they are experiencing with low-rolling-resistance tires and the lack of fuel-efficiency improvements they expected to get by using them. They wondered what other fleets' experiences have been. So the TMC conducted a survey last November and December to determine what tire performance has been. Fifty-one fleets responded to the survey, the vast majority of which had line-haul and regional-haul operations. Every fleet ran Class 7-8 vehicles and the vast majority of them (84 percent) were larger fleets with 100 or more power units. These fleets had considerable experience with low--rolling-resistance tires, as 85 percent of the respondents said they run them and 63 percent have half or more of their vehicles equipped with these types of tires. Fleets were asked to select mileage ranges such as less than 100,000, 100,000 to 200,000, 200,000 to 250,000, 250,000 to 300,000 and more than 300,000. To present the results in a meaningful way, I took the midrange of each of these mileage blocks and computed the weighted average based on the number of fleets responding in each range to come up with a mileage trend that can be used only for comparison. They do not reflect the actual mileage fleets are getting. The results were rather surprising as well as eye-opening: c Steer tire mileage (chart above) was better for low-roll-ing-resistance tires (LRR) as compared with non-fuel-efficient tires (standard). c The tread mile-age of low-rolling-resistance drive tires was better than standard tires and wide-base tires were better than either of them. The graph (left) presents the performance of drive tires on single axles (SA) as well as on tandem drive axles (TA). (I put them both on one graph to show that as fleets transition to a single axle drive, 6x2 tractor configuration, they should expect drive tire tread mileage to drop.) However, trailer tires were the exception to this trend. This is the only case where standard tires performed better than LRR tires, and wide-base tires performed the worst. As we all know, trailer tires are usually the worst-maintained position on a tractor-trailer and these tires' performance could reflect loss of tread mileage due to lack of proper inflation pressure. It may be that fleets have formed the broad perception that low-rolling-resistance and wide-base tires are delivering disappointing mileage due to the poor mileage reported on trailer tires even though this is not true for steer and drive tires. Dolly tire performance also was surprising. You might expect tread mileage of dolly tires to be similar to trailer mileage, but dollies are equipment beasts that are quite different. They are not just dragged along as trailers are, they actually push and get pulled during operation, which sets up different irregular wear patterns and wear rates than trailers. You can see in the chart near the bottom of page 10 that LRR tires performed better than standard tires and wide-base tires performed the best on this equipment. Fleets were then asked to state how much fuel economy they realized by using fuel-efficient tires. The average reported was 1.9 percent for low-rolling-resistance tires and 2.2 percent for wide-base tires. I would have expected much more for at least wide-base tires. While these data are quite interesting, what really blew my mind is the next chart (above) on fuel consumption. In this day and age, everybody seems to be focused on the high cost of fuel and reducing fuel consumption, so how could 29 percent of the respondents not know whether their fleet's fuel savings met their expectations? If they don't know how much fuel they are consuming—which is an easy number to obtain—how do they know what their tread mileage is? This is a much more difficult number to calculate. When asked, “Did fuel savings pay for lost tread rubber?” 40 percent of responding fleets said, “Yes.” If you do the math, even when diesel fuel is at a low price of $2.94/gallon—as it was in mid-March—and if you get only 1.9-percent savings in fuel economy, the $848 saved annually will still more than pay for the loss of tread rubber. (This assumes the truck runs 100,000 miles a year and achieves 6.5 mpg—savings are $848 annually or about the cost of two tires.) So those are the results from this fleet survey. Let's look at another survey done in 2003 on the state of commercial truck tire inflation pressures. Back then the Federal Motor Carrier Safety Administration (FMCSA) worked with the TMC to collect tire pressure data on 38,000 commercial trucks, tractors, trailers and buses. Only 44 percent of the tires checked were within +/- 5 psi of their target pressure. Twenty-two percent of the vehicles had at least one tire underinflated by 20 psi and 4 percent of the vehicles inspected had a least one flat tire. From these data it was fairly obvious that truck tire pressures were not well maintained in North America then, and I don't think much has changed since. We all know inflation pressure impacts both fuel economy and tread mileage. I may be going out on a limb here, but I definitely think there is a correlation between fleets that are experiencing disappointing fuel economy and tread mileage and their inflation pressure maintenance. Do you? Do you have fleets questioning the value of low-rolling-resistance and/or wide-base tires? Consider doing a fleet survey to see how well-maintained their inflation pressures are before finding fault with their tires. Also, you can provide them with tips for improving fuel economy and tire performance. Here are my Top Five Ways to Improve Fuel Efficiency and Tread Mileage: 1. KEEP TIRES PROPERLY INFLATED ALL THE TIME! Fact: Tires that are underinflated by 30 psi will lose 3 percent in fuel economy. Fact: A constant condition of 20-percent underinflation will increase treadwear by 25 percent. 2. Use technology to help keep tires properly inflated. Automated tire inflation systems and tire pressure monitoring systems (TPMS) have been proven to work and provide good returns on investments, according to both the FMCSA and the North American Council on Freight Efficiency (NACFE). Maintaining tire inflation pressure is hard work. Today, these technologies can make this work easier and faster than ever before. They are definitely worth the investment and returns are quickly seen in reduced fuel costs and emergency breakdowns. A vice president of one of the largest fleets in North America recently said to me, “TPMS is not an “if”—it is a “when.” And I have to agree with him. 3. Use fuel-efficient tires, low-rolling-resistance tires and/or wide-base tires. The key to using these tires, however, is to keep them properly inflated at all times or their fuel-efficiency advantage will be lost. 4. Keep vehicles properly aligned. Improper tandem axle parallelism can increase fuel consumption by more than 2 percent and rob tires of tread mileage. It is vital that all axles are perpendicular to the vehicle's centerline and parallel to each other, and all wheels, including those on the trailer, should track the front wheels. Keeping toe, camber and caster correct also is important. 5. Control speed. Since rolling resistance increases with speed, speed is the largest single variable that affects fuel economy. It's a fact that for every mile per hour increase above 55 mph, miles per gallon will be cut by a little over 2 percent. Therefore, a change to 55 mph from 65 mph will result in a 22-percent improvement in fuel economy and will increase travel time by about 18 percent. In addition, tread mileage will increase by about 16 percent due to reduced road friction. With the current hours-of-service regulations, fleets and drivers do not really want to turn their speed limiters back to 55 mph. However, they should be made aware of these factors if they are comparing historical data with current data and their operating speed changed during that time. The TMC meeting is a great place to learn about new technologies, trends in the industry and the basics of maintaining transportation equipment and components—and a good forum in which to raise issues and discuss equipment problems. The cool thing about TMC meetings is that there are plenty of opportunities to network with customers, suppliers and peers. In the Tire & Wheel task force meetings, representatives from competing companies work together to create recommended practices that benefit both the trucking and commercial truck tire industry. Fierce competitors become life-long friends and joke and kid each other mercilessly, adding an element of fun to the serious work that is accomplished. If your commercial tire dealership is venturing more and more into vehicle maintenance, you should be there at next year's meeting checking out how to deal with equipment problems correctly and find answers to your vehicle maintenance as well as tire questions.
Facts about low-rolling-resistance tires
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