Citing the potential for tires blistering during long runs at high speeds in excessive heat on the newly repaved two-mile oval, Goodyear and NASCAR made the decision Friday night to bring in a different left-side tire for the Quicken Loans 400.
Teams will qualify Saturday afternoon on the tire they used Thursday and Friday.
But NASCAR has added a 75-minute practice for Saturday night with the new tire in place.
The new left-side tire is harder with different construction. Thus, the tire should have less grip — meaning slower speeds — with an increase in durability.
Speeds have been an issue all week at Michigan. Drivers have turned laps as fast as 204 mph and entered the turns at 220 mph. About a quarter of the teams — 10-12 of the 48 — were having issues in practice Friday.
“We’ve got some challenges in front of us to get adjusted to the new balance in the short amount of practice,” said Matt Puccia, crew chief for Greg Biffle, who had the fastest speed of 204.708 mph in practice Friday.
“It’s all about trying to make this the safest and best race on Sunday. … What amplified it is definitely the heat. Now the temperatures have gone up, we started to see more [blistering] become more apparent.”
While crew chiefs and drivers welcomed the opportunity to practice with the new tire, it has engine builders nervous. Teams are not allowed to change engines once the race weekend starts, and the 75 minutes of practice will add significant miles to engines already being taxed because of the high speeds.
Roush Yates Engines CEO Doug Yates said the Ford teams have lap limits and will change the tuning and possibly the gearing in order to make sure the engines last.