The last time NASCAR competition officials came to Michigan International Speedway with new aerodynamics rules for the Sprint Cup Series, it was all about the drag. The package dialed up the wick on downforce, highlighted by a noticeably larger rear spoiler.
The rules and the racing it produced were widely panned as a drag in general, but not by everyone.
"We did away with that one -- unfortunately," Jason Ratcliff, crew chief for Matt Kenseth and the Joe Gibbs Racing No. 20 Toyota, said with a laugh. Kenseth led 146 of 200 laps at the 2-mile track last August to win from the pole. "I'd like to show back up with that one this time."
Since last year's experimentation with various aero trims, the pendulum has swung the other way -- far the other way. This weekend, the series will take the next step in downforce reduction with several tweaks for Sunday's FireKeepers Casino 400 (1 p.m. ET, FS1, MRN, SiriusXM) in the Irish Hills region.
The byproduct of the tinkering was a 2016 rules package that eliminated roughly 900 pounds of downforce from the previous year's 2,700-pound benchmark, helping promote side-by-side racing while reducing the aerodynamic benefits of running in clean, undisturbed air. Late last month, NASCAR announced that two 400-mile races -- Sunday at Michigan and July 9 at Kentucky Speedway -- will be run under a rules package that further chops away at downforce and sideforce stabilization, placing an emphasis on handling, plus driver skill and input.
Among the changes:
-- A smaller rear spoiler, reduced both in height (down 1 inch to 2.5 inches tall) and width (down from 61 to 53 inches).
-- The elimination of cooling fans and rear-axle offset or "skew," two tweaks that were first used in the NASCAR Sprint All-Star Race last month. Cooling fans were dropped for the remainder of the season; elimination of skew is planned only for Michigan and Kentucky.
-- A smaller, tapered fin on the rear deck lid.
-- A smaller front splitter on the sides, trimmed from 5 to 2 inches wide.
Four teams tested the new configuration during a Goodyear tire test at Michigan on May 17, a session abbreviated by rain. Though the No. 20 camp wasn't among those participating, Ratcliff said the observations shared in the garage by other teams were encouraging.
"Seems like the straightaway speeds, entry speeds, I don't know that they're up, but they're pretty fast," Ratcliff said. "And then the mid-corner speeds are down, which last year when we tested there, we went through a similar aero package, one that really separated the entry to mid-corner speeds -- or the delta -- and was much different than what we see with the current aero package."
The variation in corner speeds is designed to promote passing, allowing for "comers and goers" through the field.
"I think you don't really know until you get 40 cars on the track, but I think directionally, it's going to be good," Ratcliff said. "As far as for us, for the 20 team, we just have to do our best to be prepared for whatever it's going to be. Until you get on the track with it, it's hard to say what we're going to have. But I think the racing itself, it's a promising direction to go."
Michigan has become a laboratory for aero experiments over the last two years. NASCAR competition officials tried six configurations there in August 2014 in a 10-team test to determine the 2015 rules package. After giving the high-drag set-up an unpopular whirl during last August's 400-miler, NASCAR returned in October for a confirmation test of the 2016 rules.
Those rules have spawned much-improved racing on the intermediate-sized tracks that dominate the Sprint Cup schedule. After making further aero strides last month with rules trials in Michigan testing and the All-Star Race, Sunday's event is the next phase in the process.
An organizational test with the further-reduced-downforce package is scheduled June 13-14 at repaved and reconfigured Kentucky Speedway, ahead of the July 9 stop on the Sprint Cup schedule. While those events will help to lock in the 2017 rules package, Michigan's 400 will be the package's first audition with points on the line.
"That should be really interesting," said Brad Keselowski, a Michigan native still seeking his first Sprint Cup victory in his home state. "I heard the top speeds were really, really fast but the corner speeds were down which I think should provide a really good platform for side-by-side racing and opening opportunities to pass. It is a huge variable for our teams that they will all work through. I think it has a tremendous potential to be the future direction for our sport. That is really interesting and exciting to me personally.
"As far as how it is going to play out, you don't know. It is really unknown. That always seems to make for our best racing when we don't know what will happen."
One thing that won't happen: a repeat of last August, with teams employing the air-grabbing, 9-inch-tall rear spoilers that gave the high-drag package its signature look. The facets of that setup failed to achieve slingshot passes as hoped, but instead limited passing and produced the unintended consequence of searing cockpit heat.
Ten months later and with spoilers a whopping 6 1/2 inches shorter than last time at Michigan, it's yet another wrinkle that keeps crew chiefs hopping.
"That can be challenging and frustrating at times, but it's kind of like going to speedway races occasionally or doing a road-course event," Ratcliff said. "It's just something different, so you get to change it up a little bit and maybe get some new creativity going and don't get kind of caught in the mundane of what we do every week. So hopefully we can do the same thing as we did last fall and show up and do well."