Magazine for the professional tire industry
Issue link: https://mtd.epubxp.com/i/714120
MTD August 2016 Tire selection: 6x2 chassis "Since traction is not as much of a factor for the dead axle, a rib will suffice as long as it still fits the application," says Rick Phillips, vice president of sales for Yokohama Tire Corp. Randy McGregor, fleet manager of Transway Inc., a long- haul truckload carrier based in Holland, Mich., runs a regional steer tire on his tag axles. He says the forces acting on the tag axle tires resemble the forces acting on a steer tire more than a drive tire. "A drive tire is designed to wear properly under torque loads, not scrub loads," he says. "e rear axle has no torque on it, but it's constantly scrubbing, geing dragged around turns. e wear is closer to that of a steer axle." McGregor has been playing with tires on his 6x2s for several years now, and has seen the best combination of wear, fuel economy and tire life from a regional type of drive tire rather than a long-haul drive. "Regional drives are designed for lots of starting and stopping and high torque loads," he notes. "A SmartWay-verified regional tire still does well on fuel economy, but I find it wears beer than a really fuel-efficient drive tire." Tag or pusher? e tire-wear discussion is further complicated by the pres- ence of two types of 6x2s: the tag and the pusher-type axles. Most 6x2 offerings are the tag-type, with Volvo being the only OEM currently offering a pusher — and a liable pusher at that. While NAFCE's 6x2 report made no distinction between pusher and tag axles with respect to tire wear (pushers were not widely available when the report was published), anecdotally we hear there can be significant differences. Volvo's Adaptive Loading option lis the non-driving axle when it's not required. is obviously increases the lifespan of the tires on the liable axle, and there appear to be benefits to the drive tires as well. However, warns one tire expert, don't overlook the impor- tance of tire maintenance. "When you li a dead axle off the ground in order to improve traction, you concentrate all of the truck's load on the drive axle alone," says Brian Buckham, general manager of product marketing at Goodyear Tire & Rubber Co. "Because the truck's load is concentrated on the drive axle, even for a short amount of time, it is important to adhere to established tire maintenance practices, including running with correct inflation pressure." Inflation pressure maers We saved the controversial part for last. Most fleets, we hear, continue to run 100 psi in their 6x2 drive tires because that's the way they have always done it. But a 6x2 isn't a 6x4 and may require a fresh look at inflation pressure. ere's a small, 30-truck fleet called Ploger Transportation based in Bellevue, Ohio, that is doing something really out- of-the-box and geing some amazing results. Ploger runs several Volvo 6x2s with the Adaptive Loading system. It uses a pusher-type axle that lis when not needed. e rest of the time, Volvo uses a load-biasing algorithm to keep more weight on the driving axle for optimum traction. Ploger's director of research and development, Joel Morrow, is a driver who is out on the road every day, turning 115,000 miles a year or more. It's his job to monitor the performance of the trucks, and in this case, the tires. Ploger has been testing a Yokohama tire package for several months now on three trucks: • Drive tire: Yokohama 902L – 445/50/22.5, 20-ply load range L, 85 psi inflation • Non-driving tire: Yokohama RY407 – 445/50/22.5, 20-ply load range L, 85 psi inflation • Steer tire: Yokohama 104ZR Spec II – 315/80/22.5, 22-ply load range L, 80 psi inflation You're reading that right, 85 psi in the tandem axle tires and 80 psi in the steer tires. Drive tires in tests now are geing an astonishing 30,000 miles or more per 32nd of rubber in the center grooves of the tire. e tires on the li axle are geing slightly less than the drive tires. Both are tracking to run 400,000 miles if nothing happens to them. "I'm absolutely convinced the lower-than-normal but manufacturer-recommended inflation pressure makes a huge difference," Morrow says. "At 80 or 85 psi, the footprint is the way the manufacturer designed it to run. It's huge, and the traction is fantastic, but it doesn't seem to be hurting our fuel economy." For the record, the 104ZR Spec II, 315/80/22.5, is marketed by Yokohama Tire Corp. as a regional and long haul tour bus/ motor coach tire. Morrow says because the air chamber of the tire is so much larger than a standard 11R22.5 tire, running only 80 psi meets the load and inflation table minimums for the weight (13,500 lbs.) and provides a very smooth ride. More remarkable is the wear — or lack of it. Morrow also fully expects to see more than 200,000 miles out of the steer tires. It's clear that the 6x2 axle configuration has an impact on tires, but it may not be that alone that chews them up. ere's compelling evidence that limiting torque can improve tire wear, and that inflation pressure and tire choice can also influence wear rates. Jim Park is equipment editor for MTD's sister publication Heavy Duty Trucking. These tires are on one of Ploger Transportation's 6x2 tractors. Both have about 70,000 miles on them, the company reports. The tire on the left is a drive tire, the tire on the right is on the lift axle. 52