NASCAR has updated the superspeedway aero package in an effort to keep cars from flipping. The sanctioning body has introduced an A-Post flap for Cup Series cars.
According to a Rule Book update on Wednesday, teams will install this flap on the right front A-Post when they head to Daytona Superspeedway, Talladega Superspeedway, and Atlanta Motor Speedway. NASCAR tested this new flap at Michigan International Speedway, a track where Corey LaJoie previously flipped in the Gen 7 car.
Photo credit: NASCAR
The new A-Post flap will debut during the regular-season finale at Daytona International Speedway on Saturday, Aug. 23.
The Rule Book states that teams may modify the car's greenhouse to accommodate the updated aero package. However, they must follow very specific guidelines and template CAD files.
NASCAR has worked to reduce flips over the seasons, especially in the Gen 7 era. This car has gone airborne multiple times at different styles of tracks. Ryan Preece, in particular, flipped at Daytona International Speedway in both 2023 and '25.
Back in April, NASCAR VP of Vehicle Performance Dr. Eric Jacuzzi sat down with analyst Steve Letarte for a discussion about safety. They particularly discussed this new A-Post flap, which NASCAR was developing at the time.
"We've been working for about six months on a new aero device that is very, very, very effective," Dr. Jacuzzi told Letarte. "...It's a new flap that's going to be on the A-Post -- we're still working through some details, we've got some testing to make sure it's physically strong enough.
"We ran it on track at Michigan actually at the tire test just to see what it would do. Needed to make some changes out of that, but we're planning on Daytona -- the summer race -- we would have that ready. It's strictly the amount of time."
As Jacuzzi explained, NASCAR had some engineering to do to as it brought the A-Post flap from a concept that wasn't viable to something that was very effective in special wind tunnel testing at GM.