IndyCar will switch its engine formula for 2023 to 2.4-liter twin-turbo V6 engines augmented by a hybrid unit. Thus Meyer Shank Racing-Honda and Arrow McLaren SP-Chevrolet ran for Firestone at Indianapolis Motor Speedway on Friday, so that the series’ tire partner could gauge the possible effect of the weight increase, the revised weight distribution and the increase in horsepower.
However, Firestone also took the opportunity to carry out more ‘internal’ verification, as Bridgestone Americas’ director of race tire engineering and production Cara Adams explained to Motorsport.com.
“The main objectives of the test were (1) to test tires on cars that simulate the power increase, weight increase and altered weight distribution that we’re going to see in 2023, and then (2) to prove the tires from our new production facility. This was the first time we’d had tires from our new facility running on track and so we wanted to make sure that there were no differences, and that if there were differences that they were minimal.
“This new facility is still in Akron, less than a mile south on Main St. from our current facility, and almost right across the street from our Bridgestone Americas Technical Center. But it’s the difference in being in a building that’s over 110 years old and a building that was built specifically for this new experimental production.
“So at the test, the cars came off the trucks as they would have raced in the Indy this year. The cars were a little bit slower, running at 215, 216 in the early part of the day, but we were able to replicate everything that we needed to see. We ran a set of the current Indy tires as our control tires and then did a straight comparison with the ones from our new facility. And that part of the test went pretty well.
“Then at about 11 or 11.30 we went down for about 90mins to give the teams time to add car weight. We’ve worked with Dallara and IndyCar to make a bellhousing that could take more weight, and as closely as possible replicate what we think we’re going to see in 2023. The weight distribution went about one percent toward the rear and about 120lbs of load was added.
“And obviously the new engine formula will also see more power, so IndyCar asked Honda and Chevrolet to run their engines to replicate that power increase [60hp, just under 1.5-bar from the BorgWarner turbos, according to Bill Pappas, IndyCar’s VP of competition]. Then we tried the tires from this year – the same as we’ll use in 2022 – to again set the control, and then we ran two new right-side compounds, two new left-side compounds, to gain data from those. Once we have a little bit better idea about the actual weight and power increases and finalize the weight distribution, we’ll go back and test some more, but this test definitely got us in the ballpark regarding compounds.
“There was a little bit of difference, because we have also tuned the tires to help the cars in terms of passing, giving a bit more grip. But there wasn’t a big difference between how the current tires behaved with the cars in current configuration and how the experimental tires behaved with the cars in 2023 configuration. We tried to make sure we gathered data from the cars running in clean air and then running together, so the second car in line was in dirty air.”
Adams admitted that, as ever, it was difficult to predict tire behavior based on test data acquired on a dense-aired October day to what could be a thin-atmosphere 90-degree day for qualifying and/or the race next May.
“As you know, we could have a May that’s in the 60s or could be above 100 degrees!” she said. “So we have to plan a compound that can work in all conditions. The performance and behavior of the cars can change very much with the amount of air density, so we have to design around that, hit a median, and make sure our compound and structure covers a broad window.
“And so we note every wing angle change that the teams carry out and, more importantly, we look at all the data that comes off the car. So after the event is over, we’ll get a large data set from each car, so we know all of the wing angles, suspension settings, rollbar settings, so we can calculate the loads on the tires. Then we’ll compare that to historical race data and previous testing, and then extrapolate from there.”
Having a 21-time starter and four-time winner of the race as one of the testers was a huge help, said Adams.
“We did a little media thing with Helio before the 500 this year, and it was decided that was going to interview him,” she said. “During that interview, he commented, ‘You guys don’t test with me much any more. What do I need to do? How do I get to test your tires?’ I said to him, ‘Helio, all you have to do is win the 500 again.’ He said, ‘Really?’ I said ‘Really! Then you can test tires for us.’ Well he won the 500, so at Gateway when we announced to the teams who we wanted testing for us, I said, ‘Helio, remember the agreement we made…’ Of course he was very happy to get the chance.
“The people we test with always give us a little different feedback, everyone has a different communication style. This is the first time we’d gone tire testing with Pato and his feedback was really good. It’s good to have that relative newcomer perspective, unfiltered, whereas someone who’s been in the series for years and years, they’re expecting a certain thing and if it’s not exactly what they expect then that changes their viewpoint.
“So having feedback from Pato and feedback from someone like Helio who’s driven so many generations of cars around the Speedway and driven so many tests for us in the past, has given us a good span of experience and viewpoint.”
Next week, Josef Newgarden of Team Penske-Chevrolet and Chip Ganassi Racing-Honda’s newly crowned champion Alex Palou will test at Mid-Ohio with their chassis in simulated 2023 spec, i.e. with the new weight and new weight distribution. Pappas confirmed to Motorsport.com they will also have their turbos wound up to just under 1.7-bar boost, to represent the baseline 90-100hp increase of the 2.4-liter engines in road and street course specification. So again Firestone will get a chance to check out various tire specifications including examples produced in its new facility.
“Obviously short oval and superspeedway tires require a lot more precision,” says Adams, “but we have the same discipline constructing all our tires, regardless of type of venue. We have to, because at a road/street course you can run in even greater variations in temperature – 45degF ambient to 100deg – so between that, along with the increase in power, and the hybrid power-boost that the drivers control, the greater weight and what that does to load transference under acceleration or braking… there’s a lot to examine.
“We feel lucky to have great partners in Honda and Chevrolet and to be able to rely on their simulation capabilities to predict what the demands on the tires are going to be. But there’s still no substitute for track time.”