With the low downforce package being used this weekend for the second time in 2015, get caught up on both of NASCAR's new rules initiatives of 2015.
Low downforce package
In use: Kentucky Speedway (Kyle Busch victory); Darlington Raceway (Sunday)
Changes: Reduction in spoiler height (from 6 inches to 3.5 inches); splitter extension panel (radiator pan) decreased from 38 inches to 25 inches; splitter has 1¾ inches less overhang; and Goodyear has prepared a package-specific tire for Darlington.
Intent: Less downforce on an intermediate tracks such as Kentucky, which would lead to more side-by-side racing; increase off-throttle time in the turns, leading to more potential passing; lessen leader's aero advantage.
Key quote: "Sold. Keep doing it. Ship it." -- Carl Edwards
More: Drivers sold on low downforce
• O'Donnell lauds hard work to get package ready
• Who benefited most at Kentucky?
High drag package
In use: Indianapolis Motor Speedway (Kyle Busch victory); Michigan International Speedway (Matt Kenseth victory)
Changes: Increase in spoiler height (from 6 inches to 9 inches) and addition of 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.
Intent: High drag on big, wide tracks at 2.5-mile Indianapolis and 2-mile Michigan should lead to more pack racing and drafting; aero impact lessened on trailing car, promoting more passing and side-by-side racing throughout the field; speeds were initially projected to slow by 10 mph.
Key quote: "Everybody agrees that close, competitive racing, being able to pass -- that's important for us to continue to deliver on." -- NASCAR Vice Chairman Mike Helton
More: Drivers react after Kenseth victory
• Tweak set for Michigan
• Cars get hotter, drivers affected
• Helton addresses high drag package, concerns