The aero changes available for the Indy 500

Matt Fraver/IMS Photo
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emailBy Marshall Pruett | May 21, 2021 8:21 PM

Astute IndyCar fans will notice a number of aerodynamic changes have been made available to teams for this year’s Indy 500.

In the name of providing more tuning options and a modest uptick in downforce, new Gurney flaps (shown above) can be deployed on the front and rear wings. At the forward section of the floor, small barge boards and wing treatments have been added to the holes, and in the diffuser, strakes are optional.

In qualifying trim, wing angles will be greatly reduced and Gurney flaps might be seen up front, if they’re used at all, while strakes that focus and increase underwing downforce aren’t expected to be a common sight. For the race, all of the pieces could be used, especially if it’s hot and the air is thin. But there’s no magic combination for teams to use, and it’s in the handling needs of each driver where aero setup differences will be seen throughout the starting grid.
Strakes are common on road and street circuits, but rarely used on superspeedways. (Motorsports Images)

To dive inside the new range of options, Tino Belli, IndyCar’s director of aerodynamic development, took RACER inside the work the series and chassis manufacturer Dallara have produced for the event.

“When we originally did the UAK18 bodywork, one of our targets was to fill in the hole in the floor, but we just never had time to do it,” Belli said. “So you will see that the front half of the hole is filled in this year with an airfoil type of section that’s been carefully sculpted. It has a one-inch Gurney on the trailing edge. That is mandatory.

“To try and enable even more front downforce, we put a barge board, which is probably more correctly referred to as a vortex generator, underneath this new floor section. Now, we’ve got about 18 inches of underwing there with this barge board in place which creates a vortex, and a vortex creates low pressure. So teams can create even more downforce with that part, and we have made that part optional.”

With the new downforce from the small wings in the floor holes, and the optional barge boards, teams are no longer having to solely rely on the front wings to apply downforce on the front tires.

“This allows everybody to run lower front wing angles,” Belli said. “So the front wing is now less likely to stall out in turbulent air as well; that’s the crux of it.”

Strakes – the long pieces fitted to the diffuser that create multiple channels of concentrated air which create more efficient suction beneath the car – are a mainstay on road and street courses. They’ve also been used sparingly on superspeedways.

“We used to run then at Pocono, but they have never been allowed here at Indy before because it was felt that they created too much downforce and would be very hard to balance it with enough front downforce from the front wing,” Bell noted. “Whereas now, with the front of the floor creating a lot of downforce, we can afford to have the strakes in there, which increases the total downforce that the car can generate.”
Barge boards, the rectangular piece sticking out/pointing forward from the floor, are optional for the teams. (Joe Skibinski/IMS Photo)

With all the new items installed, Belli reckons they contribute “about 100 to 115 pounds of downforce.”

The extra horsepower and unfriendly temperatures meant taking all of the extra downforce-adding pieces for qualifying wasn’t a foregone conclusion.

In climbing from the 1.3bar/18.8psi of boost used from Tuesday through Thursday to the 1.5bar/21.75psi for Friday, Saturday, and Sunday, a significant sum of 90hp was being sent to the rear wheels. Additionally, with that heightened speed to try and carry into the corners, the rising ambient and track temperatures meant teams might need more downforce during time trials.

“The teams have a little bit of a balancing act to do,” Belli said. “The strakes are optional parts, as are the barge boards, but if you use them, they aren’t free; there’s a drag penalty to them. They are very efficient, but they’re not free. So you might see teams remove them in qualifying and put them in for the race, or choose them for both, or whatever they happen to prefer.

“Now, the other thing to consider is that if you were to look from the front of the car, the barge boards are fairly in line with the strakes. And a strake is more effective without the barge board than it is with the barge board. The barge board actually hurts the flow over the strake. So the teams have to again do a balancing act: They’ve got quite a few variations they can play with. And I’ve seen all of the variations out there this week.”