The Physics
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Speed of a Car: Le Mans (Steve McQueen 1971)

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The year is 1970 and endurance racer Michael Delaney (Steve McQueen) is back at le mans, one year after a deadly accident that killed his rival driver in an an accident involving his Gulf Oil sponsored Porsche 917K and his rival's Ferrari 512LM. The widow of his rival, who is also his friend, questions the drivers' need for speed. Delaney returns to face his other rival Erich Stahler, also racing for Ferrari's Le Mans team. Both teams get involved in a series of accidents, including Delaney's Porsche. Stahler's Ferrari suffers from mechanical problems. In the final duel, Stahler, in his repaired car and Delaney, in a teammate's car, go all out to the finish line in a heated competition.

The movie

All cars in the movie are real Le Mans spec vehicles. Even the camera car is a modified Ford GT40 with its roof cut off and camera mounts attached. Some scenes were filmed from the real 1970 Le Mans. The scenes have not been sped up and Steve McQueen, being an accomplished racer himself and having placed second in the 12 Hours of Sebring, did his own driving. The rest of the cars were handled by real, professional drivers, not just an ordinary stuntman.


I wanted to determine if I could calculate the speeds of the cars in the movie, during certain sections. Since speed is distance per time, I thought I could time a car between two landmarks and find how far it was between the landmarks.

For the first lap, where the cars leave the pits from the standing start, it took 4 minutes and 3 seconds for the white Porsche 917 to go around once to the point where the checkered flag would later be waved. I started timing from when the opening flag dropped until the car reached the white line drawn into the ground as a lap marker. From the website Le Mans Track Maps, I found out that one lap was 13.469 km back in 1970. Using the formula

v = s/t

where v is the average velocity (speed), s is the distance and t is the time it took to cover the distance, I divided the lap distance by the lap time.

v = s/t = (13469 m)/(243 s) = 55 m/s

(Which is 123 mph or198 km/h)

I looked over the movie again and saw that I could time the distance between the Dunlop Bridges. This time, however, I needed to find the distance between the Dunlop Bridges and it had not been given in the map I used earlier. I hunted around and found a website with a 2002 track map, complete with distance markers, but since 1970, the track had been altered and the infamous Dunlop Bridges had been torn down. By comparing the 2002 map with the distance markers and the original 1970 map, I approximated the distance between the bridges to be 700 meters. The lead Porsche 917 had covered it in approximately 20 seconds.

v = s/t
v = (700 m)/(20 s)
v = 35 m/s (which is 78 mph or 126 km/h)

I went back and looked at the opening scene. Here Michael Delaney is having a flashback of his accident one year before. You see his car go through the 200 meter maker, then the 100 meter marker. I timed the car between the 2 markers and found that it took approximately 2.7 seconds to cover the 100 meters.

v = s/t = (100 m)/(2.7 s) = 37 m/s

(Which is 83 mph or 133 km/h)

These speeds seem feasible, since the average speed of the Porsche 917 with the fastest lap time at Le Mans was 244 km/h (152 mph).Vic Elford, the driver of the white, long tail Porsche 917 in the real 1970 Le Mans, was the first to break the 241 km/h (150mph) average lap speed barrier. He was hired by Steve McQueen to do the "high speed close-up action driving" in the movie.

The Dunlop bridges were between a series of curves called "the esses". This causes drivers to slow down to around 120 km/h (75 mph).

In the opening lap which I timed, the cars had to accelerate form rest. When Jackie Oliver set his record in 1971, he had already been driving for a few laps and had gotten a feeling of the car. The winners of the 1971 Le Mans had been only going 222 km/h (138 mph) on their fastest lap. Over the years, due to safety concerns and added track sections meant to slow cars down has reduced the average lap speed to be around 205-220 km/h (127-137 mph). This saved lives, but some believed that the challange of Le Mans had been reduced.

Leo Tam -- 2005

Physics on Film
  1. Feature Films
    1. Tension in Spider-Man's webs
    2. Speed of a car: Bad Boys II
    3. Speed of a car: The Blues Brothers
    4. Speed of a car: The French Connection
    5. Speed of a car: Le Mans (Steve McQueen 1971)
  2. One Reelers
    1. Speed of a car: C'était un Rendezvous
    2. Speed of a car: The Run
  3. Short Video Clips
    1. Speed of a baseball: Bird Baseball
    2. Speed of a cliff diver: Iraqi Olympic Diving
    3. Speed of a motorcycle: Loading a Bike
    4. Speed of a snowmobile: Snow Jump