NASCAR Cup Series, striving for more competitive racing, announces rule book update

NASCAR Cup Series cars will use a simplified diffuser on short tracks and road courses this season.

As part of a continued push for more competitive racing, Cup Series teams received a technical bulletin Wednesday afternoon introducing aerodynamic changes for races on those tracks, including the Charlotte Roval.

NASCAR hopes the significant rule book update — a “simplified rear diffuser with fewer vertical strakes” for cars on short tracks and road courses — will help cut downforce in the front while increasing the size of the rear spoiler.

“At the test, we noticed an improvement in traffic,” Eric Jacuzzi, NASCAR’s vice president of vehicle performance, said in a release. “The car did not lose rear downforce when it yawed, which is an issue we fight with the current car. The drivers would be able to slide around more on the short tracks and really have to be less careful about putting power down. We felt that would be a benefit, and that was the big takeaway from the driver feedback. At the test, they felt they could really tell that it was more forgiving. They felt they could slide the car.”

Jacuzzi is referring to a two-day event NASCAR held in December at Phoenix Raceway — the site of the season’s first short-track race (March 10) under these new rules — where six teams raced with these new components. They provided positive feedback and felt it was an improvement from a similar test last summer at Richmond Raceway, where the experimental splitter produced too much of a reduction in downforce and stability, NASCAR said.

Last October’s Charlotte Roval brought back stage breaks, hoping to increase competition on the Concord track’s road course. The race had plenty of action, including 10 lead changes and a last-lap push from wins leader William Byron.

But 41-year-old AJ Allmendinger stole the show, dominating the final stage and leading for a field-best 46 laps.

The field could be even narrower when Cup Series cars hit the Charlotte Roval with this simplified diffuser.

This story was originally published January 10, 2024 at 6:14 PM with the headline "NASCAR Cup Series, striving for more competitive racing, announces rule book update."