NASHVILLE, Tenn.-Bridgestone/Firestone Inc. is field testing a 60-series radial truck tire for class 8 vehicles-the tractor-trailer rigs commonly used in long-haul trucking. The prototype 60-series tire is intended as an alternative to the 19.5-inch tires currently being tested by some U.S. fleets.
With its shorter sidewall, the 60-series tire, size 255/60R22.5, is comparable in overall diameter to a 19.5-inch tire and offers similar advantages, plus one more potentially significant one: The 60-series tire fits on a standard 22.5-inch rim.
Advanced tire construction technology makes it possible for the 60-series tire to carry the same load as a standard 75-series truck tire, with virtually no loss in ride comfort, according to a BFS spokesman.
However, the new tire's short sidewalls will increase the pressure on the casing when operating under load, calling into question what kind of shape it will be in after its original tread life and whether it will be retreadable.
``We'll be collecting data on retreadability in our field testing,'' the BFS spokesman said. ``It's one of the key areas we'll be looking at.''
The move to truck tires with smaller overall diameters, whether 19.5-inch or 60-series, has been driven by trucking fleets that want to increase their ``cube''-the cubic capacity of their trailers.
With the existing highway infrastructure, including overpasses and tunnels whose heights are fixed, it's not practical to build taller trailers.
But running on small tires allows the trailer floor to be lowered without changing overall height.