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VINTAGE: Benz SLR Coupe, Rare And Very Valuable
Just two hardtops were built from the SLR roadsters that ruled sports-car racing in the early 1950s.
Wouter Melissen  | http://www.ultimatecarpage.com  |  Posted July 27, 2010   Goodwood (GB)
A Mercedes-Benz 300 SLR Uhlenhaut Coupe built in 1955 made a roaring appearance on the track at the 2010 Goodwood Festival of Speed. (Photo: Wouter Melissen)
On May 1, 1955, Stirling Moss and his co-driver, journalist Denis Jenkinson, completed what has gone down in history as one of the finest drives ever. Together, they won the daunting Mille Miglia rally in a record-breaking time of 10 hours, seven minutes, 48 seconds and an average speed of nearly 98 mph, all on public roads.

The record stands to this day and was the result of Moss' fantastic driving, Jenkinson's pioneering use of pace-notes and their exquisite steed: the Mercedes-Benz 300 SLR.

Chassis 0008/55 seen at Goodwood was the second SLR coupe completed, built to compete in the Carrera Panamericana through Mexico. After the Le Mans tragedy, the race was cancelled, never to be run again. (Photo: Wouter Melissen)
Today, the surviving 300 SLRs, none in private hands, are considered among the most valuable collector cars in the world. Recently, one of only two SLRs ever fitted with permanent roofs, known as the Uhlenhart Coupes after chief engineer Rudolf Uhlenhaut, appeared at the Goodwood Festival of Speed. Restored to running order, the superb coupe was driven up the Goodwood hill by racing greats Sir Jackie Stewart and Mika Hakkinen.

The story of the 300 SLR began around 1952 when Mercedes-Benz returned to racing shortly after production had recommenced after World War II. In the years leading up to the War, the Silver Arrow Grand Prix cars built in Stuttgart were virtually unbeatable. Many of the talented engineers that developed those cars were still employed by Mercedes, so it was just a matter of time before the company picked up racing again. It was a well-planned effort, taking into account the modest financial means that were available.

Dubbed the 300 SL, the first all new racing Mercedes-Benz race car was built for the 1952 sports-car competition. The car was actually not all new as it used the running gear and suspension of the top-of-the-range 300 luxury sedan. The existing parts were bolted to a bespoke tubular space frame and covered with an elegant two-seater coupe body. Despite its production-car roots, the 300 SL was immediately successful, winning the 1952 editions of the 24 Hours of Le Mans and the Carrera Panamericana.

The steeply slanted 3-liter straight-8 produced up to 340 horsepower using direct fuel injection and desmodromic valves. (Photo: Wouter Melissen)
At the end of the year, the 300 SL was retired from racing and further developed into the legendary Gullwing road car. Meanwhile, the competition department continued its work around the advanced space frame. Next on the agenda was a Grand Prix car for the revised Formula 1 regulations of 1954. Dubbed the W196, it combined the space-frame chassis with a bespoke eight-cylinder engine. Piloted by the likes of Juan Manuel Fangio and Stirling Moss, the W196 absolutely dominated F1 in 1954.

In 1955, the Mercedes-Benz racing program was further expanded with the 300 SLR sports racer. It was effectively a two-seater version of the W196 and third development of the original space-frame design. The chassis was not the same as its predecessor’s as the SLR used torsion-bar springs front and rear. The suspension was by double wishbones at the front and swing axles at the rear. Like the W196, it sported in-board-mounted drum-brakes on all four corners to lower unsprung weight.

What really set the 300 SLR apart from its competition was the fantastic W196-derived straight-eight engine that was mounted steeply inclined to the right to lower the frontal area. What made it special was the use of both direct fuel injection and desmodromic valve actuation. Unlike a conventional setup that uses springs to close the valves, a desmodromic system uses the camshaft to both open and close the valves. The valve springs are a weak link and without them, the engine could rev considerably higher.

Engine displacement was increased to three liters from the 2.5-liter engine of the W196. Unlike the W196 engine, the 300 SLR unit was not cast but constructed from sheets of a silicon-and-aluminum alloy known as silumin. Depending on the state of tune and fuel used, it produced anywhere from 276 to 340 horsepower. All this power was transferred to the rear wheels through a five-speed gearbox that was in unit with the final drive. Using this transaxle design moved more of the car's weight to the back, creating a better balance.
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Wouter Melissen

UltimateCarPage.com

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