In 2017, the Porsche Supercup celebrates its 25th anniversary. The one-make series has, alongside the various national Carrera Cup Championships, used its level playing field to allow the best up-and-coming racers to rise to the top. Two decades before the Supercup was even formed though, Porsche was involved in another one-make series, one with a unique aim: to find out, across the worlds of Formula 1, NASCAR, IndyCar and sports cars, who was the greatest driver of all.
For North American readers, IROC will likely be more familiar in Chevrolet or Pontiac circles, while in Europe, the International Race of Champions enjoyed little publicity over its 30-year run. However, before the succession of Camaros and Firebirds, the first series was actually run using 15 identical Porsche 911s: the IROC RSRs.…