Detroit Grand Prix IndyCars are testing sustainable tires this weekend

The IndyCar racers blasting down Detroit's riverfront this weekend are doing more than trying to get to the finish line first.

The 27 cars taking to the 1.7-mile, nine-turn Detroit Grand Prix course are racing using tires made with sustainable materials as well as burning renewable fuel in their engines.

The effort is part of the racing series’ attempt to reduce its environmental impact, and at the same time test technologies that could end up on street cars someday.

This weekend in Detroit, racers are expected go through 434 Firestone Firehawk tires using rubber made from the guayule plant. Guayule (pronounced why-YOO-lay) is a shrub that is native to the Southwest desert. In a related sustainability program, cars racing on Indy 500-style oval tracks this year will use 5,150 Firestone tires made from recycled plastics.

"It's great to see sustainability becoming important to motor sports," said Cara Krstolic, Firestone director of race tire engineering and manufacturing.

Firestone, a part of global giant Bridgestone, plans to sell guayule tires for street cars by 2030.

"We’re demonstrating it in motor sports before commercializing it in passenger tires and other high-performance applications," Krstolic said.

Bridgestone aims to use 100% sustainable materials and be carbon neutral by 2050. Carbon neutrality is particularly challenging. Carbon black, a material made largely from coal, coal dust or petroleum, is a major component of tires.

The guayule tires, recognizable by their green sidewalls, will be used on all four IndyCar street circuits this year.

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Only the tires’ sidewalls consist of guayule rubber, but the guayule shrub's latex is essentially identical to latex from the rainforest Hevea trees used in today's tires.

"The big difference in guayule is how close it's grown to us," Krstolic said. Bridgestone grows guayule for its tires in Arizona.

"We can also extract latex from the whole plant, and the trees grow slower and require more space," Krstolic said.

Native guayule plants require only half as much water as cotton, alfalfa and other crops currently grown in the Southwest. "It can be grown anywhere that's arid and hot," she added.

Only tires used in IndyCar's four street races will get guayule sidewalls this year because Firestone doesn't produce enough for the thousands of tires race teams will use on permanent tracks like the Indianapolis Motor Speedway, Krstolic explained. Bridgestone will make more than 1,900 guayule tires for IndyCar races this year.

While guayule works for racing sidewalls and likely for future street tires, the natural rubber can't withstand the stress racing puts on the "contact patch" — the part that touches the road.

Hence the recycled plastic, made from materials provided by Shell Oil. Made from post-consumer plastics, the recycled product replaces the petroleum-based synthetic rubber previously used.

Shell also is providing a fuel made from sugar cane waste and other nonfood wastes. Shell claims the fuel, which the race cars’ 2.2L twin-turbo V6 engines burn, just like gasoline, reduces greenhouse emissions 60% compared with emissions from fossil fuel.

In addition, IndyCar series’ car haulers and other trucks are all using renewable diesel fuel — vegetable and animal fats, including used cooking oil. IndyCar says the fuel reduces greenhouse emissions by as much as 85%.

The Detroit Grand Prix says it also will invest in Michigan-based forest restoration and preservation to offset the estimated carbon footprint of all race attendees’ travel to Detroit.

Contact Mark Phelan: 313-222-6731 or [email protected]. Follow him on Twitter @mark_phelan. Read more on autos and sign up for our autos newsletter. Become a subscriber.