Nick Tandy and Patrick Pilet’s overall race victory in the 2015 Petit Le Mans at Road Atlanta aboard a GTLM class Porsche 911 RSR will stand as one of the greatest upsets in IMSA WeatherTech SportsCar Championship history.

Starting 35th in the 37 car field after a qualifying infraction, Tandy and Pilet began the race trailing 18 GT entries that in turn started 30 seconds behind the 16 Prototype and Prototype Challenge class entries.

They didn’t stay there very long as the Road Atlanta circuit caught the rains from the trailing edge of a major storm.

The wet track played to the advantage of their Porsche teammates and fellow Michelin fitted GTLM competitors.

Before long they were slicing through the Prototype Challenge field and nibbling at the top Prototype class.

The Pit Stop Shuffle

But each time that the Porsches, Corvettes, Ferrari and BMWs, fitted with the latest Michelin WEC series wet tires, worked toward the overall race leader, their gains were negated by various incidents requiring caution periods and the appearance of the safety car to reset the field.

Under IMSA rules, the Prototype and PCs may pit on the first lap that the pits are open. GTs are allowed to pit on the following lap. As a result, on each restart, all of the remaining Prototypes, even cars that were several laps down, were back in front of all of the GT leaders.

Breakthrough

Finally, mid-way through the race, a long green flag run enabled the GTLM cars to pass the Prototypes and re-emerge in the front group after their own pit stops.

On lap 125, the No. 4 Corvette took the overall race lead. At that point GTLM cars held the top four overall race positions.

Defining the timing 

With technical rules designed to maintain a stratification between the four IMSA classes, a Prototype lap at Road Atlanta should be proximately six seconds quicker than a GTLM lap.

At stages during the 2015 race, the GTLM cars had not only overcome that margin, but gained an additional two to three seconds per lap.

In the wet, a top driver, like Tandy, will leverage the Porsche’s rear mounted engine and weight distribution to maximize traction out of the turns. For others, a well-balanced car was enough to leverage their tires.

The end game

As the race moved into darkness, and the GTLM cars led by Tandy’s Porsche gained the upper hand, the Prototype leading Action Express team split its strategies on a caution period, leaving the No. 31 car of Dane Cameron out and pitting the No. 5 of Christian Fittipaldi.

Before long, Tandy moved his Porsche into the lead with a bold outside pass into turn one. When the No. 24 BMW moved into second place, the game was essentially over and as conditions deteriorated, IMSA officials had little choice but to call the race after seven hours and 51 minutes.

In the Books

Through the years, the Dodge Viper, Corvette Racing and TRG Porsche GT teams have all scored well-deserved overall race wins in the Rolex 24 At Daytona as their pace, reliability and the attrition of the Prototypes saw them prevail.

This one was different. Very different.

At the 2015 Petit Le Mans, the GTLM Porsche of Tandy and Pilet and the second place overall No. 24 BMW of John Edwards, Lucas Luhr and Jens Klingmann simply out ran the entire field.