Roof flap

A roof flap is an aerodynamic safety device on race cars, primarily stock cars, that deploys to prevent the vehicle from lifting off the ground during a spin. Stowed under normal operation, the flaps activate when the car faces backward, disrupting airflow over the roof to reduce lift. NASCAR mandated roof flaps in 1994 after two 1993 crashes: Rusty Wallace barrel-rolled at Talladega Superspeedway and Johnny Benson Jr. flipped at Michigan International Speedway.

The devices were developed as an alternative to further restrictor plate reductions, with primary engineer Jack Roush stating they were created so NASCAR would not slow the cars more. Flap sizes increased with the Car of Tomorrow in 2007 and again for Generation 6 bodies in 2013, which also introduced canvas parachutes for faster deployment. In 2026, after a trial at the 2025 Coke Zero Sugar 400, NASCAR mandated additional A-post flaps in the Cup Series.