Steve McQueen was the early choice for the lead role. A first meeting with producer Edward Lewis went very bad and McQueen showed no further interest in the role. He later starred in another racing movie, Le Mans.
John Frankenheimer refused to film cars moving slowly, then speed the film up. He felt the average moviegoer would be able to notice the difference.
James Garner did all his own driving. During breaks in filming there were several mini races in which Garner either tied or bettered the professional drivers hired for filming.
Yves Montand's character, Sarti, tells how he no longer slows down when he sees an accident. He uses the exact words of the real life driver Phil Hill, as quoted by Robert Daley in his book "The Cruel Sport".
Toshirô Mifune's own voice was heard in his performance as Izo Yamura at the film's premiere, but afterward he was dubbed by Paul Frees in all general release and roadshow prints.
Average Shot Length = ~5.4 seconds. Median Shot Length = ~4.7 seconds.
Crowds can be difficult to manage simply because of the effort needed to maintain their concentration. During the filming of Grand Prix there was a scene where a flaming car is driven into the pits. It was about 4 o'clock in the afternoon and the director, John Frankenheimer, was disgusted by the crowd's lack of reaction to the dramatic action during the rehearsals. They appeared to be more interested in their tea break. Frankenheimer called his special effects man over and told him to 'blow up the tea van' when given the signal. The unit went for a take. The flaming sports car came into the pits. The crowd looked on. The signal was given and the tea truck exploded. The crowd reacted and Frankenheimer got his shot' This is an extreme example of how to direct crowds. (from "Production Management for Film and Video" by Richard Gates)
During filming, Yves Montand spun out and subsequently was terrified to go fast again. The crew modified a racecar that was then towed behind a Ford GT40. This setup would reach speeds of 130 mph. Montand was more comfortable with this setup than with having to drive the car himself.
Early in the movie, Yves Montand's helmet design is that of John Surtees, who was driving for Ferrari at the beginning of the 1966 season. But Surtees left Ferrari for Cooper after two races, and therefore footage of the real Ferrari with Surtees driving was no longer available. Mike Parkes replaced him at Ferrari, and Montand's helmet design changes to that of Parkes for the remainder of the movie. No reason is given in the movie for the change.
Filming required the use of all existing Panavision 65mm cameras.
Frankenheimer's first film in color.
In the scene at the reception after Sarti wins at Monaco, Hugo comments that Sarti can now talk to kings. Sarti replies that so can any man, but will the kings listen? Or something to that effect. This is an obvious paraphrase of a famous part of Shakespeare's Henry IV, Part I, Act III, Scene i, lines 53-55: Welshman Owen Glendower: "I can call spirits from the vasty deep." Harry Hotspur: "Why, so can I, or so can any man. But will they come when you do call for them?"
Of the 32 drivers who participated or were seen in the film, five died in racing accidents in the next two years and another five in the following 10 years.
Swedish actress Harriet Andersson was cast as the female lead and filmed some scenes. James Garner wanted to replace her so Eva Marie Saint got the part instead. No explanation was given.
The cars had to be fitted with spark plug radio noise suppression kits similar to the ones used on passenger cars because otherwise the static produced by their engine electrics interfered with the radio-controlled camera mounts on the cars.
The cars that were used in the film, supposedly Formula 1 cars, were in fact Formula 3 cars made up to look like Formula 1's. Footage of real Formula 1 cars, shot during the actual Grand Prix races of 1966, was used as well.
The film shows racing taking place on the banked oval section of the Autodromo Nazionale Monza in Italy, but in fact the oval section of that racetrack had not been used for the Formula 1 Italian Grand Prix since 1961. This section of the track was still used, however, for races involving other classes of cars until 1969. The Monza 1,000 Kilometre, for example, reserved for the Sports, Prototype and Grand Touring categories, used the full 10KM course (including the high-speed banked oval section) from 1965 to 1969. Ironically, the tragic fatal accident in the 1961 Italian Grand Prix (which took the life of German driver Wolfgang Von Trips, and 14 spectators) did not occur in the banked oval section but just prior to the "Parabolic" curve, which is part of the Road Course section of Monza. This road course, with modifications for safety and since the retirement of the banked oval section, has comprised the entire circuit at Monza ever since.
The Formula 3 car's smaller engines could not spin the wider Formula 1 tires realistically on starts, so the tires were wet with gasoline for those shots, which not only allowed them to spin realistically but also caused them to smoke realistically as they spun.
The helmet design that James Garner's character uses is that of then-Grand Prix race driver 'Chris Amon (I)'. The only difference was a silhouette of a Kiwi bird that was normally on the side of Amon's helmet (he was from New Zealand) that was left off of Garner's, as his character was an American.
The helmet design used by Brian Bedford is that of then second-year driver and future triple World Champion Jackie Stewart. Of the four actors, Bedford is the only one not to do any actual driving, which explains why in all segments where the Scott Stoddard character is shown driving, he has the balaclava up to his goggles.