Sixteen cars failed inspection before Thursday's Sprint Cup practice at Daytona International Speedway.
NASCAR confiscated the teams' roof flaps, which are designed to keep cars on the ground during spins and wrecks at high speeds, for further inspection. Penalties could be possible.
The cars involved included all three Joe Gibbs Racing entries (Kyle Busch, Denny Hamlin and Matt Kenseth), all three Roush Fenway Racing entries (Greg Biffle, Carl Edwards and Ricky Stenhouse Jr.), all three Michael Waltrip Racing entries (Clint Bowyer, Martin Truex Jr. and Michael Waltrip) and both Roger Penske Racing entries (Joey Logano and defending series champion Brad Keselowski).
NASCAR inspectors made teams install new, unaltered roof flaps before drivers were allowed on the track for the first of two practices.