Wide single tires may lower rollover risk

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For carriers and owner-operators still considering whether to replace traditional duals with the new generation of wider single tires — marketed as a lighter, more fuel-efficient alternative — there may be evidence of another advantage.

In recent tests, researchers at the Center for Transportation Analysis at the Oak Ridge National Laboratory in Tennessee found a decreased propensity for rollover when tractors and dry vans were equipped with modern super singles over standard duals. A study of the tests was released Monday, Nov. 14 at the 2005 International Truck and Bus Safety and Security Symposium in Alexandria, Va.

One of the study leaders, H.E. “Bill” Knee, said researchers put a tractor-trailer with traditional duals, dynamic sensors and outriggers through a series of tests to emulate three events that lead to rollovers: evasive maneuvers, driving around curves with a constant radius, and running off the road. The same tractor-trailer was re-equipped with singles and a wider slider trailer suspension in various configurations and put through the same paces.

The result? In most cases, new generation single tires and slider suspensions reduced rollover propensity, at least in van operations. In evasive maneuvers, the new-generation combination decreased the maximum trailer roll angle per lateral acceleration ratio by 45 percent, a significant amount, Knee said.

A wider suspension spreads out the center of weight, as do super singles, Knee said. “Replacing the standard duals with the new generation of super singles effectively moved out the center of where the weight was on either end by 3 inches,” Knee said. “That gives you a 6-inch wider area. We expected that.”

Some anomalies need further investigation, Knee said. For example, a truck equipped with duals coupled to a trailer equipped with singles and a wider slider suspension performed best in the evasive maneuver test. That may have something to do with driver feel from having dual tires on the tractor, Knee said.

Further tests are planned for tankers and flatbeds, Knee said.