Firestone gaining “useful data” from IndyCar Thermal Club test

There have been questions asked regarding the usefulness of IndyCar testing on a track about which they have no data and on which their teams have no history. But the 2.9-mile Alan Wilson-penned roadcourse – a combination of Thermal Club’s North and South circuits – near Palm Springs, CA. has been faster than originally predicted. And while drivers predicted its nature would most closely resemble the Portland International Raeway, Firestone predicted its surface would behave more similarly to Barber Motorsports Park.

Krstolic (née Adams) told Motorsport.com: “We have a really good relationship with IndyCar, and Jay [Frye, IndyCar president] and his team have people come out to get a good idea of what the surface looks like. We looked at the aggregate of the surface and it appeared to be something that had quite a bit of grip.

“So we then worked with Chevrolet and Honda to see what their simulations were telling us would be predicted speeds and lap times. That helps us narrow down the window of what tire we’re going to bring, and from everything we saw, it was going to be closest to Barber. The 2023 Barber tire is the same we’re running here, which is pretty similar to the 2022 Barber tire but with a bit more grip than we had in previous years.

“Thermal Club has a lot of grip. We were out measuring track surface friction yesterday, and whereas a lot of road courses have a coefficient of friction in the 1.0-1.1 range, this was 1.2 and maybe even higher.”

Although the track is situated in the dry Coachella Valley region of Riverside County, CA., Krstolic said Thermal Club doesn’t suffer the same issues of varying grip from sand blowing onto the course as Laguna Seca or, in previous years, Sonoma.

“The surface itself is a lot less sparse,” she said, “and by that I mean the pieces of rocks in the bitumen are a lot more spread out, which does allow for a lot of mechanical grip. So even if there is a bit of sand on the surface, it will behave a lot better than other courses [because the sand falls into the gaps between the rock pieces].”

Krstolic said the course was also fast and varied enough that Firestone has been able to gauge the behavior of the tires longitudinally as well as laterally.

“We're getting very useful data. There’s a good combination of different types of turn – some quite high-speed turns and that area of the pavement is a little bit more smooth – but looking at the track as a whole, we are able to give back surface analysis to the teams so they can compare when they look at their tire data from other race venues.”

Krstolic said there have been no surprises between pre-test predictions and reality, a quarter distance into the test, aside from a couple of abrasive curbs.

Regarding the season as a whole, she said to expect a few changes, but not major ones – aside from Firestone utilizing the eco-friendly guayule tires which debuted on the Nashville street course last season.

“Everything will be pretty similar as far as road course and street course compounds,” said Krstolic. “We’ll see guayule at more venues than we did in 2022. We’ll see some changes on ovals, although Indy compounds will stay the same.”

Krstolic also confirmed what champion Will Power and others were hoping would happen: that the reversion of Indy NXT (formerly Lights) to running Firestone rubber would benefit IndyCar when it came to track surface evolution over the course of an event.

“Yes, we’re expecting when you run on the same types of rubber, the same ‘family’ of rubber compounds, you’re generally going to have more grip. When we first went from supplying IndyCar and Indy Lights to just IndyCar [in 2014], we heard comments from drivers that our tires were different, or not quite the same as the year before, and it was because they were running over another tire manufacturer’s [Cooper] rubber at the start of a session, until it got rubbered in with Firestone compound.

“So I think with us now supplying Indy NXT, IndyCar drivers are going to see a little more consistency in the tires right from the start of a session, if Indy NXT was the previous series on track.”