NASCAR officials issued technical updates for the 2026 rule book on Friday, including specifics for the Cup Series’ rules configuration for 750-horsepower tracks and a mandate for A-post flaps at every track.
Competition officials announced Oct. 8 that the Cup Series would increase engine output to a target 750 horsepower at tracks measuring less than 1.5 miles in length. Those tracks will use the short-track/road-course rules package introduced to the Cup Series in 2024, with a three-inch rear spoiler and fewer diffuser strakes.
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Five tracks will shift from the intermediate-track rules configuration to the short-track/road-course package for 2026: Bristol Motor Speedway, Darlington Raceway, Dover Motor Speedway, Nashville Superspeedway and World Wide Technology Raceway at Gateway.
Competition officials also mandated A-post flaps for the Cup Series at every track, starting next season. The body post — which runs from the hood’s edge to the roof along the windshield’s sides — is equipped with a flap designed to deploy in tandem with roof flaps to reduce the possibility of liftoff in the event of a spin.
The change was made for superspeedway events only last season, starting with the regular-season finale at Daytona International Speedway, but will now be implemented for each race in 2026. Additionally, officials specified that the surface underneath the flap must be bright orange, instead of merely a high-visibility or contrasting color.
NASCAR officials also established a new set of rule book parameters outlining testing procedures for new manufacturers (OEMs) entering any of the three national tours — Cup Series, O’Reilly Auto Parts (formerly Xfinity) Series or Craftsman Truck Series.
In each series, testing guidelines for prospective new manufacturers include:
- A maximum of three tests for new OEMs, with each test limited to a maximum of three affiliated organizations with two vehicles each
- Tests must be a maximum of two consecutive days each
- Tests to be completed by March 1
- Tests prohibited at tracks that have been repaved, are new to the schedule, or that will host events within 60 days of the test session
Competition officials expect to release sporting rules and procedures updates in January.