KANSAS CITY, Kan. -- NASCAR's two top technical officials on Friday explained the rationale behind rule changes for the 2017 season that were released to competitors earlier this week.
The minor changes are being made to improve safety and hopefully create more competitive racing.
Modifications for Sprint Cup Series cars include a smaller rear spoiler and shallower front splitter, intended to reduce the overall downforce level. The 2017 rear spoiler will measure 2-3/8 inches by 61 inches.
NASCAR ran Sprint Cup Series races this summer at Michigan International Speedway and Kentucky Speedway using a 2½ inch by 53-inch spoiler in an effort to simulate the 2017 aero package, but the competition was not as close as hoped.
"Our objective here is to get more off-throttle time for the drivers," said Gene Stefanyshyn, NASCAR senior vice president of innovation and racing development. "If we take downforce off, the corner speed will slow down and the driver will be off-throttle more. The splitter and the spoiler reduction was done in concert because we wanted to retain the same balance in the car.
"We tried a 53-inch wide spoiler but went back to the 61 after we got some feedback from the drivers," he added. "They just needed a bit more in the rear, so we fine-tuned it that way. It gives the car a bit more stability."
Drivers were generally positive in their reaction to the new rules.
"I believe anything we can do to take aerodynamic dependency away from these cars makes the racing better, makes it more fun and showcases the driver's talent and the crew chief's ability to change," said Carl Edwards of Joe Gibbs Racing. "That's good stuff."
"We are all wanting slower center of corner speeds," added six-time Cup Series champion Jimmie Johnson, who will remain at Kansas on Monday to test the 2017 package in his Hendrick Motorsports Chevrolet.
"We all feel that will put on a better race. Directionally, that is the way the sport is going and I think the smaller spoiler is going to help us."
For restrictor plate races at Daytona International Speedway and Talladega Superspeedway, the plate openings have been decreased by 1/64 of an inch in an effort to reduce horsepower and contain speeds.
NASCAR will also reduce the number of tires allotted to competitors on race weekends and will require drivers to start races with the tires used for qualifying.
Safety changes include a strengthened floor section near the pedals and modifications to the steering column to prevent the steering wheel from pushing back into the cockpit in a frontal impact. Roof hatches will be mandatory at restrictor plate tracks and optional elsewhere.
"We work on safety on an ongoing basis and agree as an industry that there is no compromise when it comes to safety," Stefanyshyn said. "When we do find something and it's significant and needs to be handled, we will handle it in a proper way."
NASCAR continues to crack down on efforts to create a rear-steering effect by skewing the angle of the rear axle, and rules regarding chassis construction in the rear axle area have been tightened up for 2017.
Friday at Kansas Speedway, Kyle Busch and Kyle Larson were held out of the first 30 minutes of Cup Series practice because they attempted to bring their cars back into rear axle angle compliance after last week's race at Charlotte Motor Speedway by violently swerving during the cool-down lap.
"We asked them not to swerve and they swerved, so they're in the garage," said Scott Miller, NASCAR senior vice-president of competition. "That was pretty specific. We told them [in September at New Hampshire Motor Speedway] that we would look at our resources after the races, and we've been doing that."
Stefanyshyn and Miller added that while they hope the 2017 package forms a solid base for the long term, they would not rule out NASCAR selectively testing out new ideas during races as it prepares for 2018.
"Nothing ever stays the same, so moving forward, we will look at more efficient ways to actually potentially test possible packages for the future," said Miller. "I think we did a good job the last couple of times with the races. That's really the best way to collect data - at an actual event.
"Hopefully we can get out in front of it a bit further with a bigger cross section of race tracks if we have some proposed new things in the future."