Michelin race tire engineer Donnie Wilson has victories here at Sebring with Corvette Racing and Andretti Green Acura. He won’t give away the strategy for the Cytosport Muscle Milk Porsche RS Spyder prototype team he is working with in today’s race, but was willing to take a few minutes between the race morning warmup and the start of the 12 Hours of Sebring to give us a peek into race tire strategies.

“The track was fairly cool this morning for the warm -up at 8:00,” said Wilson. “The ambient (air) temperature was 52 degrees and the concrete on the pit lane was 56 degrees. The asphalt part of the track was about 5-6 degrees warmer and that will be the case during the race. We track the air temperatures as a reference, but all the tire decisions are based on the track temperatures,” said Wilson. 

“At the start (10:30am) I expect the air temperature to be between 65-70 degrees and the track to be in the mid 70’s,” said Wilson. “During the day, we expect the air to peak at about 75 degrees around 3pm. By then the  asphalt part of the track will be in the  mid-90s. This will be the warmest day we have had all week. We have clear, blue skies so there is direct sunlight on the race track and that heats the track, especially the asphalt.  It should stay in that range  until about 6pm, at that point the air starts to cool, but the track retains the heat until about 7:30 or 8:00pm.”

“We have to start the race on the tires we qualified on, so we will start on Michelin medium compound tires and will probably stay there most of the day. I expect we will do some double-stints.”

To manage tires throughout the day, Wilson and the Michelin race tire engineers working with different teams will adjust tire pressures on each new set of tires and possibly switch compounds depending on the balance of their respective cars and the track temperatures. “We take the pressures down a bit during the peak of the day, then start raising them a bit as the track starts to cool. The cross-over point for me is about 75 degrees,” said Wilson. “When the track temperature gets to that point, I may look at going to my soft tires the rest of the way.”