There’s an underlying unknown with the Chevrolet and Honda aerodynamic bodywork packages that will debut in competition this week during the Verizon IndyCar Series’ Firestone Grand Prix of St. Petersburg.

Verizon IndyCar Series teams have had limited opportunities to evaluate the performance characteristics of the components and multitude of optional elements that increase downforce and reduce drag, so there is about as much driver and team personnel intrigue as there is by fans.

Underneath the Dallara IR-12 chassis, however, the primary and alternate Firestone Firehawk tires for the March 27-29 season opener are the same specification as last year.

“We’re confident that those specifications will be fine, but we’ll be watching closely — as we do at every race — how we could improve things for street courses later this season or next year,” said Dale Harrigle, chief engineer for Bridgestone America’s Motorsports and manager of race tire development.

Harrigle, like many Verizon IndyCar Series drivers, expects lower lap times at road/street courses on the Firestone Firehawk alternate tires. Each of the 24 drivers entered in the 110-lap race on the 1.8-mile, 14-turn street circuit won’t experience the effects of the alternate tires until qualifications March 28.

“There is no question that with the increased downforce that the alternate tire, with its increased grip, is going to lend itself well to the car and we expect to see a significant increase in speed on the alternate tire,” Harrigle said. “Where we’re going to all be learning – Firestone and the teams – is how the aero kits affect the gap between the primary and alternate tires in the race.

“The teams are not allowed to test on the alternates; the alternates are designed to be a little bit of the unknown to teams so we’re all going to be learning during the race.”

Each entry, which will receive seven sets of primary and three sets of alternate tires for practice, qualifying and the race, has to run at least two green flag laps on both primary and alternate tires.

Firestone Racing has been collaborating with INDYCAR since the germination of aero kits, and was an active participant during all phases of manufacturer development.

“As INDYCAR resolved their volume boxes and it became apparent what Honda and Chevrolet were going to be able to do with the freedom that they were given to design their cars, we started working closely with Honda and Chevrolet to make sure that we watching the loads that were being developed and that they were sharing the simulation data,” Harrigle said.

“We were getting simulation data from INDYCAR, which was doing a parallel program. So we worked closely with the three groups. As they were providing us simulation data, we were running tires on our indoor testing to make sure that basically the tires could keep up with the loads and speeds that were being talked about with the aero kits.

“Ultimately, with all the decisions that were made, especially with the decision to put the hole in the floor (of chassis) for safety and a couple of other items, we determined that the current tire would be a good fit for the car with the aero kits.”

That’s a testament to the performance characteristics of the tires. Firestone Racing engineers and track support personnel attended all but one manufacturer test between Oct. 6, 2014, and Jan. 18.

“That’s when we used the 2014 spec and determined that yes in fact what we were providing was a good fit for the cars and we used that testing to help us move forward with our plans.”

Manufacturer tests were conducted on a variety of road courses and ovals. The road/street course aero platform also will be used on short ovals such as Iowa Speedway and The Milwaukee Mile. The speedway aero kits are scheduled to be delivered to teams by April 1.

“We ran on ovals with both manufacturers during their development phase and then at Texas Motor Speedway on March 14 with Ed Carpenter and Helio Castroneves (for a Chevrolet test session),” Harrigle said. “We use those tests to learn where the car is going to be with the aero kits relative to the ovals.”


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