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Cutting rolling resistance

With the price of fuel seemingly stuck in the $3 per gallon range, every drop saved makes a difference. Engines and other drive train components plus driver behavior remain the controlling factors behind fuel consumption, but every part of a truck has an opportunity to contribute to fuel economy. Roughly 25 years ago, commercial trucking made a wholesale conversion from bias ply tires to radials in a search for lowered rolling resistance. Today, a series of improved truck tire tread designs from Goodyear Tire & Rubber Company promises the possibility of boosting fuel economy by up to 4%.

Introduced at the Goodyear test facility in San Angelo, Texas (a destination that requires a determined intent to reach), Goodyear officials said that the new Fuel Max technology applies to retreads on existing tire casings as well as new tires. Goodyear research shows that tire tread factors including design, nonskid depth, and rubber compound make up more than half the rolling resistance of a tire. The new treads are available for steering, drive, and trailer positions.

In testing the performance of the new Fuel Max designs, Goodyear used the standard SAE test methods driving at highway speed at the company proving grounds with results showing an 8% gain in fuel economy. However, trucks do not operate at constant speed on flat terrain for 10 hours at a time. To account for real-world conditions, Goodyear engineers adjusted the test results to include varying driver behavior, changing road conditions and terrain along as well as differing vehicle aerodynamics. These adjustments suggest a 4% improvement in economy compared to Goodyear's previous highway tire designs.

The new designs will be available in the Unisteel series as G395 LHS steering axle tires, G305 LHD drive tires, and G316 LHT trailer tires sized as standard 11R22.5 or low profile tires in 295/75R22.5 and 285/75R24.5 tires.

New drive tread

Drive tires are designed for high traction as well as low rolling resistance, important because drive tires account for almost half of total rolling resistance for a tractor-trailer combination. The casing uses an all-steel, four-belt package with optimized belt angles, Donn Kramer, Goodyear's director of commercial tire marketing says. The tread has large, stable blocks of rubber 26/32-inch deep to help reduce tread squirm in operation. In addition, the drive tire tread design has a closed shoulder to promote even tread wear and two circumferential and extended lateral grooves for traction in all weather conditions. In addition to new tires, the Fuel Max design is available for G305 UniCircle and Precure retreads. The UniCircle retread is a splice-free tread with 24/32-inch tread depth that is placed on a casing like a rubber band. The Precure retread offers 22/32-inch tread depth.

The G395 LHS steer tire also uses a four-belt package in the casing. The three inner belts are steel, and the top belt is made from polyamide to protect the steel belts from moisture. As with the drive tires, the belt package is intended to reduce tread squirm. The G395 LHS is a five-rib design and uses a pressure distribution groove on the outer edge of the shoulder rib. The pressure distribution groove bottom has a larger radius than previous designs to reduce pressure build-up, which could lead to irregular wear and cupping. The three main ribs have lateral sipes and slots for improved traction and handling.

In a typical five-axle combination, trailer tires contribute 41% of total rolling resistance, Goodyear says. For doubles combinations, trailer tire rolling resistance increases to 62% of the total. Like its tractor axle counterparts, the G316 LHT trailer tire design uses four belts, all steel in this instance, in the casing. Triple-compound construction helps reduce energy generated within the tread. The design has a solid shoulder rib and borrows the pressure distribution groove from the steering axle tire. Tread depth is 12/32-inch. UniCircle and Precure retreads are available.

Using $2.85 per gallon and 120,000 miles per year in its calculations, Goodyear suggests that improving fuel economy by 4% could save fleets up to $2,100 per truck per year.

The trailer tires and drive tires are manufactured at the Goodyear plant in Topeka, Kansas. Goodyear builds the steering axle tires at its plant in Danville, Virginia.

TAGS: Components
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