When Rudolf Uhlenhaut, the architect of the 300 SLR racer, was at the 1955 Mille Miglia to watch Mercedes’ success, he was also mulling over the idea of fitting the 300 SLR racer with a closed top for endurance events in the future.
His musings came to fruition in the shape of a competition coupé with the performance that no other road-going sports car could match. The two-seater recorded a speed of 290 km/h during a test on a closed section of motorway outside Munich. Impressed by its extraordinary performance over a cross-country trek of 3500 km (over 2000 miles), the test reporter from the Swiss magazine Automobil Revue had this to say:
“We are driving a car which barely takes a second to overtake the rest of
the traffic and for which 200 km/h on a quiet motorway is little more than
walking pace. With its unflappable handling through corners, it treats the
laws of centrifugal force with apparent disdain …”
The 300 SLR racer was based on the famous W196 Formula One champion of the 1954-55 season. The abbreviation SLR stands for Sport Light-Racing (Sport Leicht-Rennen). Considered one of the most beautiful racecars of all time, the new SLR was equipped with a slightly different straight-eight engine, which was expanded to displace 3 litres. Two of the nine 300 SLR rolling chassis, namely 0007/55 and 0008/55, were converted into 300 SLR Coupés with a closed-top body and gullwing doors. They were intended for the forthcoming Carrera Panamericana.
The body of the SLR coupé was panelled in sheet Elektron, a magnesium alloy that is even lighter than aluminum. The semicircular windscreen generated very little wind resistance. As in the SLR racer, the coupé driver had to control the pedals with his legs apart behind the steering wheel. Under the bonnet was a longitudinally-mounted eight-cylinder engine, which was placed just behind the front axle, developing peak torque of 234 lb-ft at 5950 rpm and a maximum output of 310 horsepower at 7400 rpm.
Owing to safety concerns following the tragic accident at Le Mans back in June, Mercedes-Benz decided to pull out of motorsport at the end of the 1955 season. As a result, the SLR coupé project was shelved and never went into production. Subsequently, Rudolph Uhlenhaut appropriated one of the coupés for his personal use. Weighing only 1,117 km and capable of 290 km/h, the Uhlenhaut coupé was by far the fastest road car of its time in the world.
Although the 300 SLR coupés stopped short of racing seriously, chassis 0007/55 was no stranger to motorsport racing. It served as a practice car for the factory racing team at the 1955 Swedish Grand Prix in June and the RAC Tourist Trophy in September. At the Targa Florio, which was the last round of the 1955 World Sports Car Championship, entrants practiced assiduously for a total of 16,695 kilometres to get familiar with the 72-km circuit and its meandering 900 curves. The Mercedes team was no exception — with Stirling Moss practicing hard at the wheel of chassis 0007/55. In the process, he did certain damage to the car, causing the frame to be distorted at the front right and the wishbones to be bent. But it didn’t keep him and Fangio from taking a 1-2 finish with their SLR racers at the Targa Florio on October 16, 1955.