Chief among the changes will be the use of a nine-inch spoiler — three inches taller than what was used this past weekend at New Hampshire Motor Speedway and nearly six inches taller than those used at Kentucky.

NASCAR officials hope the alterations will lessen the aero impact on the trailing car and promote more passing and side-by-side racing throughout the field on the 2.5-mile track.

"In the end, it’s all about that 9-inch spoiler," Dave Wilson, President & General Manager, Toyota Racing Development, USA, told NASCAR.com. "Everything else about the package is really about balancing the car."

Wilson said he believes the changes are intended to "create this bigger pocket of air behind the car and allow for the cars behind to draft up and slingshot, go 3-4 wide, (promote more) passing and all that."

"The question that we all have," he said, "is what is it going to do once you get up to the car through the corners? There is so much air coming off that spoiler now … how does that impact the cars next to it. We don’t know."

Spoiler Alert: Compare the spoiler we will run at Indy (left) to the one we ran at Kentucky (right). #NASCAR pic.twitter.com/mkrc9dIkfu

— Joe Gibbs Racing (@JoeGibbsRacing) July 21, 2015

The high drag package is also scheduled for use next month when the Sprint Cup Series returns to Michigan International Speedway.

A similar version of the lower downforce rules package used at Kentucky is earmarked for Darlington in September, and could potentially be implemented for races in this year’s Chase for the NASCAR Sprint Cup. Five of the 10 Chase races will be contested on tracks 1.5 miles in length.

There are no tracks, however, to which the high drag package would relate in the Chase.

Joe Gibbs Racing driver Kyle Busch won at Kentucky, and Toyota teams swept four of the top five spots with the lower downforce package. Wilson said that was due in part to the strength of the JGR organization, particularly at the 1.5-mile track, and because of the work done by Toyota to prepare for the aero changes. The Indy/Michigan changes are more of an unknown.

"We tried to optimize everything we could based upon what NASCAR gave us at Kentucky," Wilson said. "We’re doing the same thing (for) Indy. But we can only run one (car) in the wind tunnel, right?

"We can do some simulation. Typically we do a lot of drafting simulation to try and understand what happens to the cars behind, but you really rely on correlating that to real world, on-track experience. That’s when it all comes together. The low downforce package, we had some experience with it … we had some idea. But this is unchartered territory for everybody."

Cole Pearn, crew chief for Martin Truex Jr. and the No. 78 Chevrolet team, said while the effect of the package at Indy is still an unknown, it could produce "a full-on pack race" when the series returns to Michigan next month.

"It’s going to be close to that because we were borderline wide open in practice at least through (Turns) 1 and 2, not 3 and 4 in the first race (at MIS)," Pearn said. "Now, hands down we’re going to be wide-open. It’ll be interesting.

"It’s created a big scramble for us because it’s just all the aero-mapping that needs to be done and the amount of wind-tunnel time. It’s a good business for being in the wind-tunnel business right now."

The changes will likely lead to a greater amount of off-throttle time for drivers, according to Dave Rogers, crew chief for JGR driver Denny Hamlin.

"You’re really going to use more brake to slow down to negotiate the corner," he said. "You’re going to be off the gas a lot, so it’s really going to reward the teams that hit their setup the best, and it’s going to reward the drivers that can manage their tires the best.

"I think the aim is to create pack racing and see if that creates more excitement at those big ovals. I’m speculating here, but I’m speculating that we’ll be probing our fans to see what they want to see. Do they want to see the off-throttle time and cars slipping and sliding, or do they want to see a pack race and slingshot moves and all that? Some of the fans are going to like some, and some are going to like the other, just like us racers. Some of us like the pack and some of us like to see these drivers out there earning their paycheck.

"I’m one of those — I want to see them slipping and sliding."

In addition to the 9-inch spoiler, the Indy/MIS package will also feature a 1-inch wicker bill; a rear fascia extension panel similar to that currently used for superspeedway events; a 2-inch leading edge on the splitter; and a 43-inch splitter extension panel.

"Probably the biggest spoiler is when we had the 8-inch spoiler on these cars," Roush Fenway Racing driver Greg Biffle said. "… I’m a fan of the low downforce. Every time we’ve had shorter spoiler or less spoiler, and less side force and whatever else and the cars get sliding around a little bit and they’re not as fast in the corner, it’s just better racing and better passing, and it allows you to pass."

In addition to the aero changes, the following will also be in effect for this weekend’s Spring Cup race:

• Engine change: teams will be allowed an engine change before Saturday’s qualifying

• Data acquisition will be allowed during Friday’s three scheduled practices.

• Teams have been asked to bring four different rear-end gears; a determination of which will be used with the package will be made after Friday’s final practice. Teams are expected to start with a 3.70 gear.

No Tow, Just a Tire

When Martin Truex Jr. and Ryan Newman suffered flat tires during the first two practice sessions at NHMS this past weekend, both cars remained on the track until the tires could be replaced.

According to NASCAR officials, concern over potential damage to the cars was the reason given for not having each towed back to pit road.

Truex Jr. (Furniture Row Racing) experienced a flat during Friday’s opening practice; Newman (Richard Childress Racing) cut a left rear during Saturday’s first session.