Rear Spoiler Height For the Cup Series, the rear spoiler height has been adjusted from 3.5 inches to 2.35 inches. What was then the Sprint Cup Series ran tests during races at Michigan and Kentucky as 2.5 inches.
Roof Hatch For both the Cup and Xfinity Series, a roof hatch is now mandatory at both Daytona and Talladega. It remains optional for all other venues.
Restrictor Plates at Daytona, Talladega The size of the holes in restrictor plates used at Daytona and Talladega will now be 7/8ths of an inch from 57/64ths of an inch.
Lastly, NASCAR is now requiring Cup and Xfinity teams to use toe board energy absorbing material at the two restrictor plate tracks to strengthen the driver foot box. This was a response to the 2015 NASCAR Xfinity Series crash at Daytona that sidelined Kyle Busch for 11 races when he broke a foot and a leg respectively. The material adds 20 pounds to the cars' overall weight and NASCAR has raised the minimum weight of the cars by that amount to encourage them to use the material in all events. AutoWeek