The 1955 24 Hours of Le Mans began on June 11, with Pierre Levegh behind the wheel of the #20 Mercedes-Benz 300 SLR run by Daimler-Benz. American John Fitch was Levegh’s assigned partner in the car, and he would take over driving duties later. Competition between Mercedes, Jaguar, Ferrari, Aston Martin, and Maserati was close, with all the marques fighting for the top positions early on. After just over two hours of racing and approximately 6:26 pm local time, Levegh was following Mike Hawthorn’s leading Jaguar D-type along the pit straight at the end of Lap 35. Hawthorn had just passed Lance Macklin’s slower Austin-Healey 100 when Hawthorn began slowing to make a pit stop. Hawthorn, whose Jaguar had disc brakes, slowed much more quickly than other competitors using drum brakes, such as Levegh’s Mercedes. The sudden braking by Hawthorn caused the recently passed Austin-Healey to swerve to the centre of the track, attempting to repass the slowing Jaguar. Unfortunately, Lance Macklin had not noticed both Pierre Levegh and Juan Manuel Fangio, in another 300 SLR, approaching quickly from behind. Fangio was in second place at the time and attempting to lap Levegh.
Levegh, being ahead of Fangio on the track, did not have time to react. Levegh’s car made contact with the left rear of Macklin’s car as he came quickly upon the slowed car. The aerodynamic design of the Austin-Healey featured a long, ramp-like rear bodywork. When Levegh hit the Austin-Healey from behind, his car became airborne, soaring towards the left side of the track, where it impacted an earthen mound set on the side of the track to protect spectators.
The 300 SLR struck the mound at such speed and angle that it was launched into a somersault, which caused loosened and damaged parts of the car to be flung away from the car. This included the bonnet and the front axle, both of which separated from the frame and landed in the crowd. With the front of the spaceframe chassis—and thus crucial engine mounts—destroyed, the car’s heavy engine block also broke free and slammed into the crowd. Levegh was also thrown free of the somersaulting car, fatally crushing his skull when he landed.
As the remains of the 300 SLR slowed its somersault, the fuel tank, situated behind Levegh’s seat, ruptured. The ensuing fuel fire raised the temperature of the remaining Elektron bodywork past its flashpoint, which due to its high magnesium content was already very low. Magnesium’s properties mean that a combustion in oxygen is possible at relatively low temperatures, allowing the alloy to burst into white hot flames, sending searing embers onto the track and into the crowd. Rescue workers attempting to put out the burning wreckage were initially unsuccessful, as they unknowingly used water on the magnesium fire, which only intensified the inferno. As a result, the car burned for several hours. In total, 80 spectators were killed either by flying parts or from the fire.
Fangio, driving behind Levegh, narrowly escaped the heavily damaged Austin-Healey which was now skidding to the right of the track, in his path. Macklin then hit the pit wall and bounced back to the left, crossing the track again. He impacted the barrier near the location of the now burning 300 SLR, leading to the death of another single spectator, although Macklin survived the incident