Speeds slower but new tires require changes: Speeds from Saturday's practice slowed by five to six miles per hour with the new left-side tires NASCAR mandated for Sunday's Sprint Cup race at Michigan International Speedway. NASCAR and Goodyear called for the change that left teams scrambling late Friday when tires began blistering because of excessive heat buildup from high speeds created by the newly-repaved track. Greg Biffle posted Saturday's top lap at 195.647 mph, down from the 199.093 mph he posted in race trim on Friday. In qualifying trim before the tire change, Biffle posted a fast lap of 204.708 mph. NASCAR made the move to avoid blowouts and another catastrophe such as the one at Indianapolis in 2008
, when a competition caution was called every 12 laps because tires were blistering and blowing. The consensus after Saturday's practice, despite slower speeds and ill-handling cars, was the switch was necessary even though several top drivers had no issues with blistering on Friday.
But the swap did pose problems for crew chiefs and engineers scrambling to figure out setups and adjustments for the new tire. Most teams were limited with the number of laps they could put on their engines because they were near the maximum for a weekend. Fourteen drivers ran less than 25 laps. The new tire, a much harder compound, was used at Charlotte Motor Speedway in 2006 and 2007 after a repave. As expected, it gave drivers less grip and made the cars harder to handle. The new tires arrived at Michigan shortly after noon on Saturday after being delivered from North Carolina. There wasn't enough time physically to get them here in time for an earlier test, so tires used the past two days during a test and practice were used for qualifying.(see full post and many quotes at ESPN.com)(6-17-2012)