KOBE, Japan (Oct. 13, 2009)—Sumitomo Rubber Industries Ltd. claims its latest run-flat tire design, using four proprietary technologies bundled together as “thermal control technology,” provides ride comfort equal to or better than standard tires while maintaining run-flat performance.
The four technologies in use are aramid casing, high thermal conductivity materials, dimple sidewall design and SRI's Combined Technology Tire casing profile.
Bundling these technologies has allowed SRI to design a tire with a 30-percent thinner sidewall, which in turn reduces weight by 3 percent and vertical stiffness by 6 percent, the company said. The result is a tire that delivers twice the run-flat driving distance of the company's third-generation run-flat.
Using aramid fibers instead of rayon for the casing yields higher vertical stiffness, thereby reducing tire deformation and heat generation of the sidewall reinforcement layer when the tire runs a low or no pressure, SRI said.
The CTT profile uses the involute function—resembling the decreasing radius of a nautilus shell cross section—to yield a casing design with a rounded tread profile. It replaces the Dunlop Self-Supporting Technology profile SRI used in previous run-flat designs, and the tire maker claims the new design helps reduce weight and improve ride comfort.
Increasing the heat conductivity ratio of the compounds used for the sidewall reinforcement layer and the sidewall rubber—achieved through the use of carbon fibers aligned with the fibers running from innerliner to outer sidewall—improves heat dispersion away from the most critical areas, SRI said.
The company also has molded 8-mm diameter dimples into the tire sidewall to enhance airflow around the tire to achieve maximum cooling effect.
This latest run-flat iteration has been under development since 2003, when SRI rolled out its third-generation design.