NO, THEY are not super singles.
Michael Burroughes of Michelin North America Inc made that clear when he discussed ultra low-profile widebase single tires November 7-9 at the National Tank Truck Carriers Cargo Tank Maintenance Seminar.
The idea for the tires was conceived in Europe and developed in the United States, Burroughes said.
“Who knows what the future will bring?” he said. “We have engineers working five years and 10 years into the future, conducting research to change the design of the tire and how it interacts with the vehicle to make the vehicle and the transportation industry more efficient.”
Current testing of the widebase single design involves running thousands of the tires over millions of miles in both internal and fleet tests. Track testing has been used to evaluate vehicle dynamics, including sudden failure conditions. Retreadability testing also was required, and tires had to be designed for retrofitting, he said.
With testing and usage underway, two core advantages have been shown in fuel and weight savings.
“There has been a documented, demonstrable minimum fuel savings of 4% when converting from comparable tire types such as traditional duals to widebase singles,” Burroughes said.
In addition, replacing dual assemblies with widebase single tires delivers significant reduction in unsprung weight. A tandem axle tractor trailer converted from an 18-wheeler to a 10-wheeler on aluminum wheels can achieve a minimum weight savings of 796 pounds, he said.
Other benefits include higher spring rate relative to traditional dual fitments and improved ride quality similar to changing from leaf spring to air-ride suspensions. (Higher spring rate means that the tires act as a stronger spring, all tires have a “spring” function in the vehicle suspension, and absorb a greater proportion of the energy/forces transmitted into the vehicle suspension by irregularities in the road surface and the dynamics of a moving vehicle.)
“The tire is really a suspension mechanism that absorbs some of the road shock,” Burroughes said.
The tires also improve vehicle handling with higher cornering stiffness and a subjective feel of improved control in curves.
“The tires actually increase lateral stability and lower the rollover threshold of a vehicle,” he said.
Other advantages include easier maintenance because of one tire to mount rather than two, reduced tire and wheel inventory, and one pressure check per axle end.
There are some disadvantages to the widebase singles. Depending on the nature of the application, tire life may be reduced, but the 4% drop in fuel consumption and the weight savings compensate for any shortfall in reduced mileage, Burroughes said.
Flats on the road can be a disadvantage since the driver can't “limp in” for repairs. However, fleets are reporting fewer flats with the tires. Pressure is more easily maintained, there are two extra layers of steel in the crown, and different mechanical reaction to penetrating objects is apparent.
As for the future, it's possible that trailers, and more specifically tankers, will be redesigned to take advantage of the space that becomes available because the widebase single tires take up less room than dual tires.