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Potential for Rolling Resistance Improvement

Most manufacturers OTA interviewed had similar expectations for tire rolling resistance reduction over the next decade. The expectation was that an overall reduction of 30 percent was feasible by 2005, resulting in normal tires with an RRC of 0.0065 (if the current average is 0.009). Most also believed the H-rated or V-rated tires would have similar percentage reductions in rolling resistance so that they would have RRCs of 0.009 to 0.01 by 2005.

Very similar percentage reductions in RRC for light truck tires were also expected. A 30 percent reduction in rolling resistance can translate to a 5 percent improvement in fuel economy, if the design is optimized for the tire. Manufacturers were unwilling (or unable) to estimate additional RRC reductions in the post-2005 time frame, possibly owing to their unfamiliarity with tire technologies in the research stage at this time.

These 30 percent reductions are expected to be achieved with virtually no loss in handling properties or in traction and braking. Manufacturers suggested that some loss in ride quality may occur because of the higher tire pressure, but this could be offset by suspension improvements or the use of semiactive suspension systems.

Resistance Improvement

However, manufacturers expected noise and tire life to be somewhat worse than those for current tires. Both of these factors are highly important–noise may represent a special problem because the improved aerodynamics and, possibly, electric drivetrains of advanced vehicles will reduce other sources of noise. An optimistic view for the 2015 time frame suggests that RRC values as low as 0.005 may be achievable.

Such low rolling resistance tires have already been built for electric cars. Auto manufacturers believe that such tires are not yet commercially acceptable because prototypes have suffered from losses in handling, traction, and durability.

Last Words

Tire manufacturers have expressed the view that technological improvements during the next 20 years could minimize these losses, and an RRC of 0.005 could be a realistic goal for a “normal” tire in 2015, as an average, which implies that some tires would have even lower RRC values.

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