Indy 500 race cars are running on 100 percent renewable fuel and tires with recycled plastics

Bridgestone Americas Inc., which owns the Firestone brand, is making two versions of environmentally friendly tires for IndyCar races this season.

The sidewalls of the Firestone Firehawk tires that will be used in five races taking place on street tracks, such as the Detroit Grand Prix, feature a rubber made from guayule (pronounced why-YOU-lee), a woody shrub found in the deserts of the Southwest. Guayule is probably best known as a source for natural latex, used for gloves and medical devices.

Since 2012, Bridgestone has spent more than $100 million developing guayule-based rubber for tires. As with Shell’s renewable race fuel, Bridgestone and Firestone chemists and tire engineers worked to make the guayule tires indistinguishable from regular Firehawk race tires.

With their distinctive greenwalls, these tires got their real-world test last year at the Nashville Grand Prix. Josef Newgarden, a two-time IndyCar champion who drives for Team Penske, didn’t even notice.

“Josef Newgarden got out of the car and said, ‘I don’t see any difference,’ ” said Cara Krstolic, Bridgestone’s executive director of race tire engineering and product engineering.

“So that was a great compliment that there was no difference between the two tires.”

Krstolic said that tires made with guayule are more environmentally friendly in many ways.

“The Hevea tree grown on farms in Southeast Asia is where most of the natural latex rubber comes from, so that takes a lot of water,” she said. “And then you have to get that material from Southeast Asia to the United States, get it processed and into our tire production process. Guayule is a domestic source of natural rubber. Now it doesn’t have to come by air or boat from Asia.”

Guayule requires very little water compared with Hevea, and it can grow in areas where drought and higher temperatures are common. Bridgestone grows its own guayule shrubs at a farm in Arizona, and the environmentally friendly Firehawk tires are made at the company’s Advanced Test Production Center in Akron, Ohio.