Racing vs. street tires: Both influence Firestone tire development

NASHVILLE, Tenn.—Tire development is consistently evolving, producing more innovative designs across the board. Whether it's on the race track, city streets or hometown roadways, tires need to perform for their drivers.

Few understand the demands of tire development better than Dale Harrigle, chief engineer, replacement tire, Bridgestone Americas Tire Operations, who entered the field in 1994.

"Across my more than two decades in race tire engineering, I had design responsibility for all Indy car tires in Firestone Racing's portfolio," Harrigle said.

After leaving the race tire engineering team following the 2016 IndyCar season, he switched gears and has worked with passenger tires since.

In years past, it was more common for engineers to focus in one area, Harrigle said, but at Bridgestone, it's becoming more common for engineers and compounders to move back and forth between racing and passenger tires, "as each side presents great learning and experience that can influence and improve the other."

There's also more camaraderie.

"There is more collaboration between the two sides than ever before at Bridgestone, helping promote the sharing of knowledge, tools and processes to drive breakthrough innovation in both areas," he said.

Similarities and differences

"A race tire and passenger tire share common construction features," Harrigle said, "They both have beads, body plies, belts, spirally wound plies and tread."

He noted that Bridgestone makes both race and passenger tires on similar equipment and through a similar process, but that is where the commonalities primarily end.

The projected lifespan and definition of "performance" are significant differences between the tire types.

"Race tires are designed to provide maximum grip to the driver within a very specific window of intense operating conditions and within a very limited lifespan—about 100 miles for the typical Firestone Firehawk race tire," Harrigle said.

"Passenger car tires are designed for a lifespan that can exceed 600 times that of a race tire for Indy car.

"Additionally, passenger tires must operate in a variety of weather conditions, maintain acceptable performance throughout the wear life of the tire and deliver a smooth ride with the lowest possible noise, vibration and harshness."

Another distinguishing factor between the two is how they use their compounds. For instance, Firestone Firehawk race tires tend to be softer than a typical passenger tire compound.

"The increased need for grip in race tires requires the use of very soft compounds that can grip the track at over 200 mph," Harrigle said.

Influences

There are variations, yet the racing market can influence passenger tire development.

"While they are designed and built to meet very different demands, we see race tire development influencing passenger tires in two key areas—the development of improved technology and the development of our people," Harrigle said.

"As you would expect, the technology lessons we learn from racing transition first into our high-performance street tires, like the Bridgestone Potenza and Firestone Firehawk Indy 500 tire lines. In those tires, we are in a constant, competitive battle to provide the best possible dry and wet grip, coupled with excellent wear life. These targets are very similar to the development targets for our race tires, and the racetrack provides the ultimate proving ground for new technologies that can advance and enhance our passenger tires."

Secondly, companies are working not only to produce quality products, Harrigle said, but also to attract, retain and develop talented, motivated engineers who can solve problems quickly and develop next-generation technology.

"In addition to offering the ultimate proving ground for our tires, the racetrack provides an ideal opportunity for teammates to learn key engineering and business skills in a fast-paced, high pressure environment," he added.

The racetrack is a great learning environment with near-instant feedback from knowledgeable teams and drivers, Harrigle said. It can take years to determine the success of a passenger tire in the marketplace, but with a new race tire, it's judged in its first race weekend.

On the flip side, there are times when passenger tires inspire the racing world.

This was exemplified when the Firestone Race Tire Engineering team "leaned heavily" on the advance development groups and passenger tire engineers for the Firestone Firehawk, he said, relying on their modeling and pattern expertise while developing the tread pattern of the new rain tire that was used in the IndyCar Series this season.

Rain tire development

"Developing an Indy car rain tire is one of the more difficult technical challenges that our race tire engineering team faces," Harrigle said.

"A motorsports rain tire must operate reliably over a range of conditions, from full-wet to damp, and at speeds of over 160 mph on certain tracks—all while providing the same handling balance as dry tires."

Racing in wet conditions requires a tread pattern design that evacuates water effectively, he said, which also is a key consideration in engineering passenger tires.

"With that in mind, the Firestone race tire engineering team worked not only with IndyCar drivers and teams, but with our Bridgestone Americas passenger tire engineers to design a new Firestone Firehawk rain tire that features both asymmetric and directional tread patterns," Harrigle added.

"The tools used in the development and testing of the new rain tire, including predictive modeling, also are used for all passenger tires designed by Bridgestone."

Harrigle said Bridgestone dedicates itself to producing durable, reliable products, both in race and passenger tires.

"A significant amount of engineering, testing and inspection goes into every tire we produce to confirm that we are delivering the best possible product to both the world's best drivers on the racetrack and to everyday drivers on the street," he said.