NASCAR unveils A-Post flap to keep cars grounded at drafting tracks

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In development for roughly a year, a Wednesday NASCAR Cup Series rule book update includes the formal introduction and mandating of a new A-post flap for races at Daytona, Talladega and Atlanta designed to keep cars on the ground.

The flag will make its debut at Daytona next month in the regular season finale Coke Zero 400.

This is primarily a byproduct of Ryan Preece getting airborne at Daytona in 2023 and 2025, for different reasons each time, but still emblematic of NASCAR’s desire to keep the cars on the ground.

Dr. Eric Jacuzzi, NASCAR’s vice president of vehicle performance innovation aero, detailed the issue during a podcast appearance with crew chief turned television analyst Steve Letarte in April.

“We spent a lot of time looking at this. … When Ryan’s car crossed from the track, it hit the lip of the bus-stop chicane, which was protruding about 2 inches. So we had a pretty significant tire mark there and a chunk of asphalt missing,” Jacuzzi said of the 2023 race.

“The other part … I went and looked at some helicopter research and when you hover a helicopter over pavement, the engine power is let’s say ‘100.’ When you move over to grass you need ‘120’ or ‘130’ — I believe it was 30 percent more power. That’s because of that surface. To me, it makes a lot of sense that the grass, we would have lost some of that downforce we had.”

Thus, the development of this A-post flap, which Jacuzzi told Letarte was in development even before the 2025 Daytona 500 incident.

“It started out as a concept that wasn’t really viable, and then we had a couple brainstorms and sort of came up with this idea,” Jacuzzi said. “It proved to be very, very effective.”

The flap is designed to decrease lift in the early part of the spin and reduce cars getting off all four tires.

“We think that the less lift that we can have on the car early in the spin, that’s more tire contact with the ground, more slowing it down, which is all good for us,” Jacuzzi said.

The flaps will be held down by magnets, which are connected to the flaps via cables. Once the longstanding roof flap on the car is deployed once a car spins, the cable will pull the A-post flap open.