To prepare for his role, Christian Bale took race driving lessons at the Bondurant High Performance Driving School. The school's founder had been a friend of Ken Miles, so Bale got to hear stories of the 1960s racing scene. Robert Nagle, Bale's instructor and the film's stunt coordinator, called Bale "hands down the best actor I've ever trained."
Matt Damon said that the number one reason he wanted to do the movie was to work with Christian Bale.
In order to recreate the Le Mans circuit as it existed in the 1960s the scenes taking place on the race track had to be shot in five different locations. This proved a challenge in terms of continuity as not only the cars had to be correctly placed for each shot but the weather had to be consistent as well. VFX was critical in fixing a variety of continuity issues, some of which were as simple as adjusting clocks to the right time.
According to Matt Damon, Christian Bale had to lose 70 pounds before filming began. Bale had previously gained a lot of weight for his role in Vice (2018) and had about seven months to lose it all to play the lean race car driver. Damon asked Bale how he managed to lose all the weight, and Bale replied that he simply didn't eat. Damon said he was impressed by Bale's monk-like discipline.