Upcoming races at Kentucky Speedway and Michigan International Speedway in the NASCAR Sprint Cup Series will see further changes to the Cup rules package and how it pertains to aerodynamic grip.
NASCAR announced Thursday (May 26) that the two races will be used for a test of a new package that will alter the rear spoiler, front splitter and rear deck fin of Cup Series cars in an effort to curtail downforce and sideforce.
The most recent adjustments are the latest in a continuing effort by NASCAR to bring about closer competition on racetracks the series visits. Those changes include reducing the spoiler height from 3.5 inches to 2.5, reducing the splitter to 2 inches and changing the size of the deck fin.
“I think we look at it as a never-ending journey; if we can improve, we’re going to do that,” Steve O’Donnell, executive vp of competition and chief racing development officer for NASCAR, said in a release. “We wanted to go the direction of low downforce, see how that worked, not kind of go all the way in and hope that we are directionally right. And we are seeing that play out.
“We’ve seen some great racing at the beginning of the year. But we also knew that we had some more levers that we could pull if the direction kind of proved out, so we’ve tried some of those things. We’ve tested it and what we’ve also wanted to do is lower some of the corner speeds to allow for even more passing. That was one of the areas where we’ve seen minimal change, but there are some levers we can pull to really drive that down.”
Both events will be contested this spring and summer: the race in question at Michigan will be held June 12 while the series will travel to Kentucky for its lone race of the season on July 9.
Kevin Rutherford is the executive editor of Frontstretch, a position he gained in 2025 after being the managing editor since 2015, and serving on the editing staff since 2013.
At his day job, he's a journalist covering music and rock charts at Billboard. He lives in New York City, but his heart is in Ohio -- you know, like that Hawthorne Heights song.