K to SSKL: The Mercedes-Benz supercharged cars

Nov 10, 2011
  • 1926: Mercedes-Benz supercharged cars make their racetrack debut
  • Powerful titans dubbed ‘White Elephants’
  • Victory at the 1931 Mille Miglia 1931 as the first non-Italian winner

Ahead of the merger, Benz and Daimler had agreed that the racing activities of both brands would initially be continued by DMG. This was also the background to the focus on the Stuttgart firm’s supercharged vehicles in the two years before the 1926 merger and after the completion of the operation. Mercedes had already been making racing cars with mechanical superchargers of this kind for some years. The most powerful of those vehicles was the eight-cylinder Monza car of 1924.
It was in one of these cars that Rudolf Caracciola won the first German Grand Prix for sports cars at the Avus track in Berlin on 11 July 1926. Caracciola completed the distance of 392.3 kilometres at an average speed of 135.2 km/h. To enable it to race as a sports car, the Mercedes-Benz racing department converted the body of the 2-litre Grand Prix design so that the vehicle formally qualified as a four-seater.
While the Monza racing car did not go on to play any major role in the new company’s involvement in motor racing, the first German Grand Prix did mark the beginning of a new era in motor sport. It was at this time that Alfred Neubauer, who by now saw himself more as an organiser than a racing driver, developed his idea for detailed communication between drivers and the pits with a system of flags and sign boards and a meticulously planned process during pit stops. Neubauer’s ’sign language’ was first used in the Solitude Race on 12 September 1926.
The class for sports cars over 5 litres at the Solitude Race was won by Willy Walb in his K model, first introduced in 1926. On the very same day, Rudolf Caracciola won the Semmering event in the class for touring cars with a displacement up to 8 litres, also in a Mercedes-Benz K model, at an average speed of 74.7 km/h. Caracciola also won the racing car class, in a 1914 115 hp Mercedes Grand Prix racing car, whose 4.5-litre engine was now equipped with a mechanical supercharger. His average speed of 89.8 km/h gave Caracciola another record, and also the third Semmering challenge trophy for Daimler-Benz AG.
But the star of the racing season was clearly the Mercedes K model racing touring car based on the 24/100/140 hp Mercedes. The mechanically supercharged in-line six-cylinder engine, fitted with a Roots blower, had a displacement of 6.2 litres and developed 85 kW, or 118 kW with the supercharger engaged. The K was the first member of the legendary family of heavyweight supercharged cars that enabled Mercedes-Benz to dominate the racing scene in the years from 1926 onwards. The K, S, SS, SSK and SSKL models were used for racing events, but were also available for use on the road.
1927: Mercedes-Benz S model, the first of theWhite Elephants
The 26/170/225 hp Mercedes-Benz S model racing touring car of 1927 was the first supercharged sports car in this family to be fully developed by Mercedes-Benz for racing purposes. This enhancement of the K racing touring car model is regarded as the first of the ‘White Elephant’ models. This was the at first glance rather unflattering nickname the racing community gave to the heavyweight vehicles from the S model through to the SSKL, with which Mercedes-Benz totally dominated the racing scene in the late 1920s and early 1930s. These racing cars, painted in the traditional white racing livery of Germany, were admittedly big, strong and powerful – but the other attributes of the vehicle were anything but elephantine.
In fact, the 1.9-tonne titans with their huge 6.8-litre engines consistently outpaced other competitors’ lighter, more manoeuvrable vehicles. It was in one of these cars, featuring an improved chassis set lower than in the K model, that Rudolf Caracciola achieved world celebrity. This happened on 19 June 1927, when he drove an S model to victory in the class for sports cars over 5 litres in the inaugural race on the Nürburgring track, ahead of fellow team member Adolf Rosenberger. This was the first of eleven overall and class victories for Caracciola during that season. There was also plenty of success for other Mercedes-Benz drivers, including a triple victory at the German Grand Prix for sports cars at the Nürburgring over 509.4 kilometres on 17 July 1927, when Otto Merz (overall winner), Christian Werner and Willy Walb, all driving Mercedes-Benz S models, dominated the race.
In 1927, the Daimler-Benz works team entered vehicles in more than 90 races and other motor sports events, bringing an overwhelming number of victories for the K (kurz = short chassis) and S (sports) models, in mountain and touring events as well as on the racetrack. With the supercharger activated, the six-cylinder engine of the
Mercedes-Benz S developed 138 kW at 3300 rpm. This enormous power was also coveted by private motorists – a wish that Mercedes-Benz was happy to fulfil. All the sports cars in this family were in fact also available for non-racing use, making the car the vehicle of choice on the road for affluent motorists. While private drivers also frequently entered their supercharged cars in competitive events, the enhanced racing version was reserved for Mercedes-Benz’s works drivers.
1928: Mercedes-Benz Super Sports model and its successors
The engineers and designers continued to work tirelessly on further improving the outstanding design of the S model. The result of these efforts made its debut in 1928, as the 27/180/250 hp Mercedes-Benz SS racing touring car. The extra ‘S’ in the name of the new prestige model stood for ‘super’. The most important difference from the 1927 car was the new M 06 engine, replacing the M 9856 in the S model, which was later also used in the SSK and SSKL. The ‘06’ in the engine model designation indicated that this engine was one of the first to be developed by the joint forces of the companies merged to create Mercedes-Benz. The 7.1-litre engine developed 138 kW without supercharger, and 184 kW at 3300 rpm with supercharger engaged.
The standout successes of the SS model on the race track included the triple victory at the German Grand Prix on 15 July 1928 at the Nürburgring. The drivers were forced to take turns at the wheel on account of the extreme heat. Christian Werner brought Rudolf Caracciola’s car home in first place, ahead of Otto Merz and the Werner/Walb duo. Mercedes-Benz also took three victories at the Semmering race in September 1928. Wenzler won the class for touring cars of up to 8 litres in a Mercedes-Benz S (average speed 77.4 km/h), Ernst Günther von Wentzel-Mosau was the victor for sports cars up to 8 litres in his Mercedes-Benz SS (average speed 83.8 km/h), and Rudolf Caracciola took the competition for racing cars with displacement of up to 8 litres in the new Mercedes-Benz SSK. His average speed of 89.9 km/h gave him the best time of the day.
The enthusiasm for hillclimb events in Germany resulted in the development of the SSK, launched in 1928 (the ‘K’ stood for ‘kurz’, the German word for ‘short’), technically largely identical to the SS model, but with a shorter wheelbase, at 2950 mm instead of 3400 mm, and therefore a shorter body. This made the SSK the perfect vehicle for the narrow, winding mountain roads. Rudolf Caracciola began the 1929 racing reason on a high note for Mercedes-Benz by finishing the inaugural Monaco Grand Prix in third place in a Mercedes-Benz SSK. That same month, he was the overall winner of the Zbraslav-Jiloviste hillclimb race in Prague. And in pouring rain, he won the International Tourist Trophy in Ireland with an average speed of 117.2 km/h – all in SSK vehicles.
In the Grand Prix des Nations for sports cars at the Nürburgring, raced over 508.7 kilometres on 14 July 1929, the dominant cars were the lightweight Bugattis, which scored a one-two victory. The team of August Momberger/Max Arco-Zinneberg finished third in an SSK model. The SSK was also entered in races overseas. Carlos Zatuszek scored a string of victories in his adopted home of Argentina from 1929 onwards. And driving the SSK model, Caracciola also dominated the 1930 season for
Mercedes-Benz, winning not only the Irish Grand Prix in Dublin, but also all the races he entered in the inaugural edition of the European Hillclimb Championship in the sports car class: Zbraslav-Jiloviste (in what was then Czechoslovakia), Cuneo (Italy), Shelsley Walsh (UK), Klausenpass (Switzerland), Schauinsland (Germany), Semmering (Austria) and Svábhegy (Hungary). Accordingly he was crowned as the clear winner of the European Hillclimb Championship.
In April 1930, with Christian Werner, he also competed in the Mille Miglia 1000-mile race to Rome and back, starting and finishing in Brescia. The German duo finished sixth overall.
For the 1931 racing season, Caracciola was able to compete in the new 27/240/300 hp Mercedes-Benz SSKL model, an enhanced, weight-reduced version of the SSK sports car. The 7.1-litre engine now developed 176 kW without supercharging, and 221 kW with supercharger. This gave the car a top speed of 235 km/h. Externally, the most characteristic feature of the car was the holes punched in various structural components. The holes in the vehicle frame and cross members were highly effective, making the SSKL 125 kilograms lighter. Nevertheless, the sports car still tipped the scales at around 1352 kilograms.
The 1931 season was a success from the outset, with Rudolf Caracciola and assistant driver Wilhelm Sebastian winning the Mille Miglia race in a Mercedes-Benz SSKL. This was the first time a non-Italian had been the overall winner of this prestigious race, which had been staged since 1927. Caracciola’s memories of the event, recorded later, make impressive reading: ‘1600 kilometres on dusty country roads, with ravines and steep precipices to left and right… through fearsome corkscrew and serpentine bends, towns and villages, then back to dead straight roads again at average speeds of 150, 160 or 170km/h … for a whole night and into the next day.’ The Italian drivers could have been expected to have a clear advantage – they knew the roads, and since some manufacturers had entered almost 50 cars in the event they had numerous depots with mechanics lined up all along the way. There was no way Mercedes-Benz could match such resources.
But Caracciola accepted the challenge: ‘ For sixteen hours I sat at the steering wheel, for sixteen hours we thundered through the length and breadth of Italy, following the slim beam of our headlights through the night, and on into the dazzling glare of an Italian spring day.’ And so it was that, on 13 April 1931, the first man across the finishing line as the winner of the Mille Miglia was the Mercedes-Benz lead driver, completing the course at an average speed of 101.1 km/h, and setting a new record in the process. The next Stuttgart works driver to achieve this feat would be the British driver Stirling Moss, who won the event 24 years later in a Mercedes-Benz 300 SLR.
In the 1931 season, Caracciola was however forced to race for a private team, with the factory only in a support role, since in 1931 the impact of the international recession meant the company was no longer able to finance its own racing stable. But the SSKL assigned by Daimler-Benz to its top drivers was clearly a race winner. In 1931, Caracciola also won the Eifel race, the German Grand Prix and the Avus race. And with five victories in five starts, he again won the European Hillclimb Championship for sports cars.
In the 1932 season, the Stuttgart company withdrew from motor racing completely because of the worsening economic problems. Rudolf Caracciola, forced to look for a new team, joined Alfa Romeo. Nevertheless, there was to be one more sensational success for the Mercedes-Benz SSKL.
At the Avus race in Berlin, the private driver Manfred von Brauchitsch entered one of these vehicles that he had had fitted with a streamlined body under his own initiative. The design was by the leading aerodynamics expert Reinhard Koenig-Fachsenfeld, and the panel work was carried out by Vetter in Cannstatt. The substantially improved aerodynamics of the modified SSKL, affectionately dubbed ‘the gherkin’ by the Berlin public, gave the car a higher maximum speed than the works version and resulted in a victory for von Brauchitsch. After a tense duel for the lead, he won the race with an average speed of 194.2 km/h, just ahead of Rudolf Caracciola, driving for Alfa Romeo in the absence of a Daimler-Benz works team in the 1932 season. Von Brauchitsch’s exploit earned him a place in the Mercedes-Benz racing team for 1934. However, the days of the White Elephants as racing cars were now over. A new era was about to begin, bringing even greater success for Mercedes-Benz than that achieved with the S to SSKL.
On 22 May 1932, Manfred von Brauchitsch won the Avus race decisively in Berlin in the aerodynamically optimised Mercedes-Benz SSKL. In doing so, he set a class world record with an average speed of 194,4 km/h over a distance of 200 kilometres.
Prague hill climb Königssaal-Jilowitsch “The European hillclimb championship”, 11 May 1930. Rudolf Caracciola (starting number 144) at the start in a Mercedes-Benz model SSK. Caracciola wins in the sports car class up to 8 litres. He achieves the day’s best time and sets the sports car track record.
Rudolf Caracciola´s Mercedes-Benz SSKL (W 06 model series) from 1931. This picture was taken at the German Grand Prix at the Nürburgring on 19 July 1931.
German Grand Prix at Nürburgring, 19 July 1931. Rudolf Caracciola with co-driver Wilhelm Sebastian (starting number 8) in a Mercedes-Benz SSKL sports car. After 4 hours, 38 minutes and 10 seconds, Caracciola wins in the class over 1.1 litres.
Eifel race at the Nürburgring, June 7, 1931. The winner Rudolf Caracciola (starting number 5) with a Mercedes-Benz SSKL. On the right. Racing Director Alfred Neubauer.
German Grand Prix for sports cars on the “AVUS” (motorcar traffic and practice road), 11 July 1926. Rudolf Caracciola, the winner, with his co-driver Eugen Salzer (starting number 14) in a supercharged Mercedes 2-litre, 8-cylinder racing car.
“Rund um die Solitude”, 12 September 1926. Willy Walb (starting number 27) at the start with a Mercedes-Benz model K. Winner in the category of sports cars over 5 litres. State prize, day’s best time, challenge trophy, SKF Norma.
German Grand Prix for sports cars at Nürburgring, 17 July 1927. Christian Werner (starting number 7) in a Mercedes-Benz Model S. Werner drove the fastest lap and finally achieved 2nd place in the category for sports cars of over 3 litres.
Germand Grand Prix for sports cars at the Nürburgring, July 17, 1927. Otto Merz (starting number 8) with a Mercedes-Benz S. Winner in the over 3 litre sports car category.
"Around Solitude", 18 September 1927. Otto Merz (starting number 46) in a Mercedes-Benz Model S. Merz won the class for racing cars over three litres displacement.
German Grand Prix for sports cars at Nürburgring, 15 July 1928. Triple win for Mercedes-Benz. The Mercedes-Benz team in the first and second rows with a type SS racing touring car. In starting position (from left to right): Starting number 1 - Georg Kimpel/Adolf Rosenberger. Starting number 5 - Otto Merz and co-driver Eugen Salzer. Starting number 4 - Christian Werner/Willy Walb.
German Grand Prix for sports cars at the Nürburgring, July 15, 1928. The winning team Rudolf Caracciola / Christian Werner (starting number 6) with a Mercedes-Benz SS.
Grand Prix of the Nations at the Nürburgring, July 14, 1929. The team Willy Rosenstein / Adolf Rosenberg (starting number 12) with a Mercedes-Benz SSK. Rosenstein / Rosenberg finished second in the over 3-litre sports car category.
Grand Prix of the Nations at the Nürburgring, July 14, 1929. The Mercedes-Benz team on Mercedes-Benz SSK sports cars at the start: Rudolf Caracciola / co-driver Heinrich Kühnle (starting number 2). Georg Kimpel / co-driver Eugen Salzer (starting number 4). Willy Rosenstein / Adolf Rosenberg (starting number 12) (from left).
Tourist Trophy in Ireland, 23 August 1930, scene at the start. Malcolm Campbell (starting number 1) and Earl Howe (starting number 2) in a Mercedes-Benz SS.
International Tourist Trophy near Belfast, 17 August 1929. Rudolf Caracciola wins in a Mercedes-Benz SS racing touring car.
Ralph de Palma at the wheel of his 26/120/180 hp Mercedes-Benz S, the car with which he won two races on the racetrack in Atlantic City, New Jersey/USA, on May 30, 1928.
Mercedes-Benz SS sports car of 1928.
Avus-race 1932 with Manfred von Brauchitsch
1,000-mile race of Brescia on April 12 and 13, 1931. Rudolf Caracciola and his co-driver Wilhelm Sebastian (here on the Raticosa pass) won the race on Mercedes-Benz SSKL.
1931: Manfred von Brauchitsch wins Nice - La Turbie