This weekend will see the 82nd running of the 24 Heures du Mans, or the 24 Hours of Le Mans for you non-French speakers. One of the major races of any fan’s schedule, it has long been a technological proving ground. It was originally conceived of to test the endurance of man and machine, and continues in that spirit today. However, in 1955 technological advancement and the pursuit of speed led to a mismatch in technologies that is a direct cause to one of the greatest motorsports tragedies in history.
After a 10 year hiatus due to a little war involving the entire world, the Le Mans race resumed in 1949. Technological advancements from the WW2 were quickly applied to the race cars fielded by companies like Jaguar, Mercedes, Austin Healey, Ferrari and Aston Martin. Cars became lighter, faster, and more maneuverable.
For 1955, Mercedes-Benz introduced the 300 SLR to the world. It was the pinnacle of lightweight construction. Built on a modified W196 Formula 1 chassis, the 1955 300 SLR (for “Sport Leicht Rennen” or “Sport Light Racing”) incorporated a space frame chassis and magnesium bodywork. The Formula 1 car’s inline 8-cylinder engine was used, but was canted at a 33-degree angle to reduce it’s aerodynamic profile allowing that magnesium sheetmetal to be even more sleek. Fuel injection, one of the major advancements from WW2, was incorporated. The engine valves used desmodromic actuation to reduce valve float and the stress on conventional springs. That stress was, in part, brought on by the 65/35 gasoline/benzene mixture used to fuel this beast.
In short, this car weighed a mere 880 kg (1,940 lb) but boasted a power output well north of 300 hp. Astronomical figures by the standards of its day.
Oddly enough, unlike the Jaguar D-Type it was racing against, the Mercedes 300 SLR used drum brakes rather than more efficient (and newer) disc brakes. Drum brakes are very prone to fade, a condition where the stopping power decreases as the brakes heat up. So, for the Le Mans race an air brake was fitted to the Mercededs-Benz entrants. This was necessitated by the incredible speeds the cars were reaching on the fast, sweeping course.
On race day, the ultra-light Mercedes-Benz cars faced off against the Jaguar D-Type and entries from Ferrari, Aston Martin and Maserati. The 300SLR already had proven itself at the Mille Miglia and would win the 1955 World Sports Car Championship despite the tragedy about to unfold.
Racing was tight between the top competitors and lap records were being smashed at an astonishing pace. The 300SLRs and D-Types were dominating. The Maseratis and Ferraris were dealing with technical issues, and the Porsche entrants were a hair off the pace. Heading into the pit straight Mike Hawthorne, driving a Jaguar D-Type, had just passed a slower Austin Healey 100 when he saw that his team was calling him into the pits. The disc brakes on the Jag allowed him to quickly slow and head for pit lane. Lance Macklin, driving the Austin Healey, slammed on his brakes and swerved to try to pass the slowing Jaguar. He apparently lost control.
Right on Macklin’s back bumper was the 300 SLR of Pierre Levegh, who had just been lapped by Hawthorne’s D-Type and was trying to hold off Juan Manuel Fangio. Even if he attempted to brake, the high speeds (about 150 mph) and low-tech drum brakes were a technological mismatch. Levegh ran into Macklin and the lightweight Mercedes went airborne.
Loosened by the impact, the front axle and hood went flying into the crowd. Parts of the space frame began coming apart. The highly volatile gasoline/benzene mixture in the fuel tank caught the flammable magnesium bodywork on fire. Firefighters made it worse by trying to put the metal fire out with water, further oxidizing the metal and causing the fire to burn hotter. Levegh was killed. Officially, 83 spectators were killed by debris and the fire. About 120 more were injured.
Advancements in material sciences, engine technology, and suspension design made for race cars the likes the world had never seen to that point. At the same time, a mismatch in braking technology and lax spectator safety systems occurred. Put this all together and disaster was just around the corner.
Mercedes-Benz withdrew from competition following the 1955 season and would not return until the 1980s. Jaguar also ceased its official racing program shortly after the tragedy. Juan Manuel Fangio would never race at Le Mans again. Spectator safety, always considered a minor detail to race promoters was quickly moved to the forefront of the discussion when several European countries banned racing until tracks were equipped with better safety systems for spectators. Switzerland still has its ban in affect to this day.
[Image Credit: Sports Car Digest]