Bridgestone develops, "3rd generation" runflat tyres

ERJ staff report (DS)

Tokyo -- Bridgestone Corp. said it has improved the riding comfort of run-flat tyres. The company said it will begin marketing this “third generation” of run-flat tyres in 2009, focusing on sales to original equipment manufacturers for installation in new passenger vehicles.

Bridgestone claims runflats are ecologically effective. In a statement, the company said, "Eliminating spare tyres from all vehicles would help save resources by reducing the approximately 59 million spare tyres [made] annually. Furthermore, CO₂ emissions over the spare tyre lifecycle - from raw material procurement to disposal - could be reduced by approximately 2 millions tons of CO₂ per year. Additional CO₂ emissions can be reduced by the elimination of wheels for the spare tyres.

Bridgestone's mainstay run-flat tyres are those with reinforced rubber in their sidewalls. Bridgestone's third-generation run-flats have adopted new technologies that further improve riding comfort. By application of these new technologies, the third-generation run-flat tyres can reduce vertical stiffness deflection index* more than the second-generation run-flat tyres and achieve riding comfort comparable to conventional tyres. Moreover, they enable the development of run-flat tyres in a wide range of sizes, including sizes that were previously difficult to develop.

“Heat control” is the key to the technologies that enable third-generation run-flat tyres. The simplest way to improve the riding comfort of sidewall-reinforced type run-flat tires is to make the tire sidewalls thinner and softer. However, when driving with a puncture, deformation of the tire sidewalls increases and generates more heat at that portion. How to deal with this heat generation while maintaining and increasing the durability of run-flat tyres (after they lose inflation pressure), became a major challenge in efforts to improve riding comfort. In response, Bridgestone has developed three technologies to solve that puzzle: new sidewall-reinforced rubber that can reduce heat generation, a new ply that can reduce deformation growth, and Cooling fin technology that can cool the tyre sidewalls. Because each of these technologies improves riding-comfort performance separately, Bridgestone will select the technologies as appropriate when developing commercial products. (Based on tire sizes, the weight of the vehicles and when technologies become available for practical application.)

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Press release from Bridgestone