Bridgestone Develops New 'COOLING FIN' Technology for Runflat Tires

Tokyo (Aug. 1, 2007) -- Bridgestone Corporation has developed new 'COOLING FIN' technology that expands the vehicle application potential of runflat tires. Runflat tires enable the driver to drive up to a specified distance at a specified speed (80 km at 80kph) following a loss of air pressure.

The challenge facing runflat technology was to devise a way to minimize the heat caused by deformation of the sidewall when driving on a sidewall-reinforced type runflat tire*1 that has lost air. COOLING FIN technology is a new paradigm that uses disturbances in the airflow created by protrusions on the surface of the tire sidewall -- that face in towards the center of the wheel -- to cool the tire sidewall.

This advancement allows the development of runflat tires for certain SUVs, CUVs, minivans and large passenger cars where the high tire cross-section*2 causes a significant amount of heat to be generated on the sidewall when driving with low air pressure. Previously, sidewall reinforced runflat technology was limited for use with passenger cars. Bridgestone has filed for patents on this technology.

We anticipate that in the future this technology will enable the utilization of lighter sidewall-reinforcing rubber, thus reducing overall weight and enhancing comfort during normal driving. Bridgestone will push ahead with further research and development in the field aimed at expanding application of this technology to other tires. Bridgestone plans to showcase the technology at various academic conferences in Japan and other key technology markets around the world.

Bridgestone's tire development philosophy centers on bringing 'peace-of-mind' to the driving public, as realized through an emphasis on 'the environment,' 'safety' and 'comfort.' Runflat tires are seen as the successful embodiment of this ideal. Bridgestone will continue seeking to contribute to the advancement of technology available to the motoring public through its tires.

An outline of the technology follows.

COOLING FIN technology overview

(1)Drawing of tire used in test

(2)How the cooling effects of airflow are enhanced by the COOLING FIN

1. Without the COOLING FIN, airflow does not touch the tire surface and cool air sails over the tire surface without cooling it.

2. The COOLING FIN redirects the airflow causing the upward stream of air. This upward stream sucks in the cool air and penetrates downward to the warm air around tire's surface, cooling the tire surface. (Effect of enhanced airflow)

(3) Effect of COOLING FIN: Comparison of temperature on surface of tire sidewall

The temperature of the surface of tire sidewall of runflat tires with the COOLING FIN is lower than conventional runflat tires.