Source: Ron Gross/Michigandriveins.com
I've done some digging and found no evidence Tucker did any testing at Capital City Speedway, Lansing (Spartan) Speedway, or any Michigan racetrack. The Tucker was designed, tested and built long before (1947-48) Lansing Speedway opened in 1956. There was testing done at Indianapolis Motor Speedway and this is where the rollover depicted in the movie actually took place. The movies speedway scenes at the fictional "Lansing Speedway" were actually filmed at Petaluma Speedway in Northern California. Apparently, Hollywood opted to use the Lansing Speedway name in the film instead of Indy.