Overdrive Magazine | Trucking Business News & Owner Operator Info
Issue link: http://read.dmtmag.com/i/611028
36 | Overdrive | December 2015 'Dead axle' savings For growing numbers of customers, benefits of the 6x2 drive spec outweigh the drawbacks BY JACK ROBERTS W ant to save $1,500 to $3,000 a year on fuel? One way to do it is by spec'ing a 6x2 axle. "With a 6-by-2, you get lower weight, reduced maintenance effort and costs and higher fuel econ- omy," says Mike Roeth, executive director of the North American Council for Freight Efficiency. "It's a pretty attractive combi- nation" for certain long- haul applications. The configuration is rarely considered by owner-operators. Resale value is poor, and the dis- advantages of having less traction include the risk of getting the truck stuck in almost laughably embar- rassing circumstances. However, a small but growing number of fleets now buy 6x2 tractors. NACFE's 2014 report put 6x2 market penetration at 2.5 percent. "Our prediction was that we thought that num- ber would double every year for the next four to five years and level off somewhat," Roeth says. In Europe, the 6x2 configura- tion already is considered the standard spec for long- haul tractors. If you put any credence in a forecast by the U.S. Environmental Protection Agency, by 2024, 60 percent of Class 8 trac- tors engaged in long-haul applications will be using the 6x2 axle spec because of fuel savings of up to 5 percent. North American cus- tomers can spec two variations of the 6x2 axle system from suppliers such as Dana and Meritor. Both versions feature an unpow- ered "dead axle" that nor- mally would be powered in a conventional 6x4 drive axle package. The more common system, according to NACFE, is the "tag tan- dem" configuration, where the forward-position rear axle is driven and the second-position axle is not. Alternately, the "pusher tag" 6x2 features the rearmost being powered, with a "dead" or tag front- position axle. Both versions are offered with 40,000- and 46,000- pound ratings, as on 6x4 axles. Both also feature tag axles specifically designed to carry the same load as the powered axle. The fuel economy and weight-saving benefits come from having an entire set of inter-axle driveshafts and gear sets removed. This lack of internal gearing cuts para- sitic fuel loss from internal friction and lubricant churning. "It also cuts about 400 pounds off the overall vehicle weight, which fur- ther contributes to both vehicle freight efficiency and higher fuel economy," Roeth says. To compensate for the higher power and torque loads being transmitted to a single drive axle, 6x2 inter-axle components are slightly larger and more robust than those found on 6x4 units, coupled with a 23,000-pound maximum haul weight per axle when compared to a 20,000- pound haul weight on 6x4 axles. The axles are not a good fit in regional haul or pick- up-and-delivery applica- tions on uneven terrain or poor roads because of the potential for lost traction, says Scott Perry, Ryder System's vice president of supply management and global fuel products. Ryder was one of NACFE's partners on its 6x2 test program. Normal, Ill.-based Nussbaum Transportation Services runs all 48 contiguous states with 6x2 axles.