CHARLOTTE, N.C. (AP) NASCAR will use track-specific rules packages at three more race tracks as the sanctioning body continues to try to improve the racing.
A unique rules package already had been announced for Saturday night's race at Kentucky. NASCAR executive Steve O'Donnell said Tuesday a similar low downforce package will be used at Darlington in September.
Teams will use a higher drag rules package at Indianapolis Motor Speedway later this month and Michigan International Speedway in August.
The Kentucky package is expected to cut about 1,000 pounds of downforce from the cars. Drivers have cautioned not to expect too much from Kentucky because Goodyear can't provide a soft enough tire to match the lower downforce package.
But Goodyear was able to determine a tire for the Darlington package during a one-day test last week with Tony Stewart, Matt Kenseth and Brad Keselowski.
''The ideal package for us is matching the tire with lower downforce, and when we looked at the schedule, the most ideal venue for that was Darlington, so we feel like we have the lead time for Goodyear to come in and build that specific tire, so that's why we moved forward on the Darlington package,'' O'Donnell said.
For Indy and Michigan, the aero package will feature a 9-inch spoiler and 1-inch wicker bill; a rear fascia extension panel similar to what is currently used for superspeedway events; a 2-inch leading edge on the splitter; and a 43-inch splitter extension panel. That high drag package could cut speeds by nearly 10 mph.
''You'll see some significant mile-per-hour differences,'' O'Donnell said. ''I think we we're looking at over 200 (mph) before, and kind of the 191 range that we'd be looking at now.''
Additional track time will be added to Indy, Darlington and Michigan to test the new package, and Kentucky opens Wednesday for teams to try the rule changes.
NASCAR is not expected to use any unique rules packages in the 10-race championship playoff series.