Last month, the IndyCar Series confirmed the switch of its final race on September 15 from the downtown streets of Nashville to the 1.33-mile D-shaped concrete oval in nearby Lebanon, Tennessee.
The move to have the season end on an oval for the first time since 2014 (Fontana) has pushed Firestone, the sole tire supplier of the North America’s premier open-wheel championship, in a frenzy.
Although the task is already challenging on its own, it isn’t as simple as showing up and testing right out of the gate under the current configurations or using the same tire compound from when IndyCar last raced at the oval in 2008. There is a plethora of added variables the company is forced to work through, including the expected mid-season introduction of the hybrid – a significantly heavier car that impacts tire heat distribution and wear.
In an exclusive interview with Motorsport.com, Cara Krstolic, Executive Director of race tire engineering and production for Firestone, shared that the situation isn’t as simple as bolting on tires built for other ovals, with all others notably being paved with asphalt.
“Nashville Superspeedway is a little bit of a unique construction and it's not something that we currently use,” Krstolic said.“When designing a tire for Nashville, we're looking at something that is going to be consistent and durable. The concrete speedway is definitely a challenge because it's very abrasive, it's high wear on tires, and then the shape of the oval adds a lot of heat to tires. So, we have to bring a construction that's specific to Nashville.
“It's not something as simple as bringing tires from Texas (Motor Speedway) or another speedway forward. It has its own unique demands. We have a test date secured and we will be testing compounds and constructions.
“This is a unique construction that's not in our lineup, so we need to make sure our building machines can run it. So, we'll be looking at a lot of things going up to the tire test and then building forward towards the race.”
Krstolic confirmed that a tire test with the hybrid is set for June 14, which follows an unrelenting stretch that begins on May 11 with four races over five weeks – with Indianapolis 500 qualifying filling that gap – and another tire test at Milwaukee.
“There's a lot of unknowns that we are going into the tire test with,” she said. “And so, we'll be testing the different aero configurations because we're not sure what aero configuration we're going to see yet, assuming the hybrid engine and a lot of different things that we will learn during that test.”
And the impact is not just felt in only the workload, but also budget demands. Firestone have pulled all its resources together within engineering and test time, along with shifting things around within the production schedule.
The design cycle for a new tire in advance of a new track is roughly a year and a half with back-and-forth data and analysis at multiple points throughout the process – including testing – for the design iteration. And this comes in addition to the ever-evolving compound improvements for the current circuits on the schedule.
“We are continually evolving our design,” Krstolic said. “Even a place like Indianapolis Motor Speedway, when we go there, we're learning what to do for the next year.
“Typically, we would have a year to a year-and-a-half design cycle, but we have condensed this into maybe seven months. It's a technical challenge, but we are very fortunate to have the history of the track, the resources, the really smart chemical engineers and chemists, as well as mechanical engineers that can pull from our old designs and extrapolate that to the current car.”
Considering there are only three months separating the tire test from the race weekend, it presents a tight turnaround on developing, deciding, and producing an ideal compound.
“The way we're looking at it, we have the ability to do a lot of background work and research, which is what we're doing now,” Krstolic said.
“We are going to use every bit of those seven months to be able to develop this tire. So, we are looking at old data that we could pull, working with race teams that have been there before and will be here now, looking at our past history and results, race summaries, tire wear inspections; that provides us enough time to develop be able to develop and design those tires that will be used at the test.
“And then we have the time from the test going forward, with our production schedule being very tight, we have to have a very close idea of what we're going to end up selecting at the test, and then maybe make a couple of tweaks. We'll do a lot of advanced work, maybe a little bit redundant in the design and development cycle to be able to hit go that week after the tire test with production.“We have to give production enough time to build the right specifications, mix the compounds, so there's a lot involved. It's a seven-month window from when we found out, but it's going to be quite a challenge along the process.
Krstolic shared that the production team has already been sorted around the schedule to add more help in the construction of the tire. In addition to working with IndyCar to get the maximum amount of information possible about the venue, Firestone have also sent personnel to Nashville this week to gather data.
One of the more positive points coming with the change to the oval, though, is that Firestone had yet to produce the tires specific on what would have been a new 2.17-mile, seven-turn circuit (changed from the 11-turn, 2.170-mile layout used from 2021-23).
“We've been fortunate enough to use so many tires in hybrid testing that we have not yet built for the Nashville street course race, which means that quantity is still open,” Krstolic said.
“It might be a larger or smaller quantity depending on how much we test, but it's still going to be a significant shift as far as resources. So, not wasting tires.“We're not throwing anything away and even if we had already made the tires, we would figure out a way to be able to use those as opposed to scrapping them. There's always tire-testing team testing at the end of the year. We would not throw away an entire race quantity of tires.”
And along the lines of leaving no stone unturned is the fact that IndyCar’s top development series, Indy NXT, will also be finishing its season on the oval, which also requires Firestone’s attention.
“The Indy NXT tire is very versatile,” Krstolic said. “The compounds that we're going to be using for this year are going to work at a track like Iowa, work at a track like Gateway and they'll probably be acceptable for our race in Nashville.”
However, to ensure that is the case, an Indy NXT car will also be on track during the IndyCar test to verify positives on tire wear, heat cycles and feedback from the driver.
“The good thing is it's probably a common tire specification,” Krstolic said.
“We don't know that yet, but it's likely a common tire specification. The behavior of the tires on that car is pretty consistent.
“We are working with IndyCar to determine if testing is needed after the tire test and before the race.”
