Yokohama’s BluEarth-air EF21 tire incorporates the most advanced technologies and design techniques to achieve a significant reduction in weight compared to one of the company’s flagship passenger car tires.
Developed to mark Yokohama’s 100th anniversary, it was sold in Japan on a limited basis last year in size 205/55 R16 91V.
The BluEarth-air EF21 is rated AAA for rolling resistance and an A for wet grip – the highest graded on the market according to the Japanese tire label. This is thanks to a thin yet highly rigid structure, which, compared with the Advan dB V551, has resulted in a 25% reduction in the tire’s mass.
Tetsuo Ikegami, manager and head of testing group number one, says, “We have adopted an advanced lightweight design to reduce weight and the tire’s environmental impact through using less material, conserving resources and ultimately enabling a lower overall vehicle weight.”
Including market research, development, testing and production, the program for the BluEarth-air EF21 took nearly four years in total.
A new tread compound has also been developed. Weight reduction has been achieved mainly by thinning the rubber gauge of the tread and sidewall construction.
“We have even adopted a thinner tread gauge with shallower tire grooves,” notes Ikegami. ‘With the new compound we have achieved excellent wet grip and the same mileage performance as a conventional model.”
The compound is created using a new mixing method called advanced reaction technology. This technique refines the control over the reaction, and enables improved silica dispersibility – again improving wet performance.
During the program, physical testing was particularly important, mainly conducted at the company’s proving grounds in Ibaraki Prefecture and Hokkaido Island in Japan. Vehicles used included a Toyota Prius and a VW Golf.
Ikegami says there are currently no plans to expand the amount of sizes available.