Cup teams return to MIS as NASCAR seeks to alleviate aero push

The NASCAR Sprint Cup Series headed back to Michigan International Speedway on Monday, not to race but to test a number of options for its 2015 rules package.

When the current Generation-6 car was introduced in 2013, it was supposed to provide much better racing on the fast 1.5-mile and larger ovals like MIS, which is 2 miles in length. Likewise, the elimination of the minimum ride-height rule for this season was an attempt to improve competition.

But today’s cars still suffer from so-called "aero push" — the inability of a second-place car to pass the leader because the closer the second-place car gets to the leader, the less downforce it has on its nose. And with this downforce, it can’t turn as well, which means its laps are slower.

That’s why you’ll often see fast cars advance rapidly to second place, but then be unable to pass the leader.  

To minimize aero push, NASCAR tested a number of variables at Michigan. The sanctioning body’s prime package consists of dive planes, a 9-inch front spoiler, 6 percent lower rear differential gear and a driver-adjustable track bar. Three horsepower settings — 850, 800 and 750 horsepower packages — will be tried with these packages.

NASCAR also tested a low-downforce setup with about 28-30 percent less downforce.

"Bring the cars closer together, that’s the goal," said Gene Stefanyshyn, vice president innovation and racing development for NASCAR. "The final solution and how we realize it, we haven’t determined yet."

During a media briefing last week, NASCAR officials expressed optimism about the test.

"We’re extremely pleased with the expected outcomes that we’ve developed through careful analysis using a number of technical tools," the sanctioning body said in a statement issued then. "We anticipate this test to validate the extensive work that has gone on around the racing development."