In the 1930s premier racing underwent a revolution - subtlety and design brilliance became the watchwords, rather than simply 'bigger equals better'. The reason for the change in philosophy was that for safety reasons, the officials banned the ever-larger, ever-more-powerful and ever-heavier cars that had dominated the racing in the 1920s and early '30s. In 1932 the international motor racing authority, AIACR, decided to introduce the 750-kilogram formula (weight without fuel, oil, coolants and tyres), with the new weight formula coming into force in 1934.
In spite of the economic crisis which affected all motor manufacturers, Daimler-Benz had developed the W 25 - a car later to become legendary - to meet the specifications. The W 25's eight-cylinder in-line engine with supercharger and four-valve technology developed 314hp from a displacement of 3.36 litres. Equally progressive - the car's running gear used independent wheel suspension all-round and had hydraulically-operated drum brakes.
The Silver Arrow Legend
The legend of the Silver Arrows was created in the W 25's very first Nürburgring race under the 750-kilogram formula. Despite systematic lightweight design, the cars' weight was still one kilogram above the limit. It was too late to incorporate technical modifications during the night before the race on 3 June 1934 - and so it was attributable to racing manager Alfred Neubauer's courageous decision that the legend of the Silver Arrows was born on that day. Over that night, he instructed his mechanics to scrape off the white paint from the aluminium bodywork. This unusual measure not only yielded the desired weight reduction but also provided the spectacular silver appearance of the Mercedes cars, which previously had always appeared in white livery. A few years later, the German press invented the legendary name "Silver Arrow" for the Mercedes racing cars.
Strong competition from Auto Union - their cars were, incidentally, later nicknamed "Silverfish" - eventually prompted the further development of the highly successful W 25. In the course of the years, the eight-cylinder's displacement increased further from 4.0 to 4.7 litres, and the engine developed up to 494hp, depending on the type of supercharger and fuel quality.
1935 was an extraordinarily successful year for Mercedes-Benz. The company team won nine out of ten races with the W 25 and scored five double victories; Rudolf Caracciola clinched the European and German champions' titles, and the battle with Auto Union for the world speed record attracted worldwide attention.
But in the 1936 season, Alfred Neubauer's team found its masters in the company teams of Auto Union and Alfa Romeo. The W 25 won only individual races - it had lost its dominance.
1937: The W 125 Holds off Strong Competition
The experience gained with the newly fortified competitors suggested a restructuring of the racing department - young Rudolf Uhlenhaut became the new Chief Engineer, and from his analyses of the W 25, the W 125 emerged. The chassis was modified more extensively than the supercharged eight-cylinder engine. For weight reasons, the idea of a completely new V12 was abandoned, and so the proven straight-eight engine was thoroughly revised in terms of displacement, carburettor and supercharger. These engines generated up to 646hp from a displacement of almost 5.7 litres!
With the W 125, Mercedes-Benz was again a big step ahead of all the other manufacturers in 1937. Rudolf Caracciola regained the German championship as well as the European champion's title.
The highlight in this so successful year for Mercedes-Benz was, without any doubt, the international Avus race. Hermann Lang, promoted from racing mechanic to company driver, reached an uncontested average speed of 261.7 km/h in the final heat; the top speed of 380 km/h in this race was not to be exceeded until 1959.
1938: The Three-Litre Formula Races
In the course of just a few years, the 750 kilogram formula racing cars reached ever new heights - outputs of more than 650hp and top speeds of over 400 km/h in record runs meant that the authorities called for a scaling down of engine performance. Soon introduced was a three-litre formula that limited the displacement of supercharged engines to three litres and that of engines without superchargers to 4.5 litres.
Daimler-Benz retained the supercharger principle and developed the W 154. The new, further developed car was based on the W 125 but powered by a completely new V12 engine with a cylinder angle of 60 degrees, developing 430hp from 2962 cm3 in its initial form. It is interesting to note that all the new three-litre cars were faster than the clearly more powerful racing cars entered the previous year.
The first major triumph with the W 154 was accomplished by the Mercedes-Benz team in Tripoli/Libya: Hermann Lang, Manfred von Brauchitsch and Rudolf Caracciola scored a fantastic triple victory. Against strong competition from Maserati, Alfa Romeo, Bugatti and Auto Union, Caracciola won the 1938 European champion's title for the Stuttgart-based team.
1939: W 154 Continues
After having won six races, the W 154 was systematically further developed for the 1939 season. In its further improved chassis, the V12 now developed 480hp. It was another exciting season with numerous Mercedes-Benz victories, culminating in three titles: the European champion's and German hill-climb champion's titles went to Hermann Lang; Rudolf Caracciola won the 1939 German road race championship.
1939: 1.5 litre Mercedes Win
The 1939 Tripoli Grand Prix (won by Mercedes-Benz in 1935, 1937 and 1938) was to everyone's surprise staged for 1.5 litre racing cars exclusively. Rumour had it that the organisers wanted to give the Italian manufacturers a chance to win; the marked dominance of Auto Union and Daimler-Benz in the three-litre formula races is likely to have played a role...
However, in the unbelievably short time of eight months, the Stuttgarters developed a 1.5 litre car for this race: the W 165. Its supercharged V8 engine developed a remarkable 254hp. After just a single test a few days before the race, racing manager Alfred Neubauer's team sent out Rudolf Caracciola and Hermann Lang to race against a superior line-up of 28 Italian and British racing cars.
Daimler-Benz succeeded in impressively proving its excellence with a double victory. Lang won the race ahead of Caracciola; the third-ranking Alfa Romeo was one lap behind when it crossed the finishing line. The W 165 was not entered in any other races in 1939 because those responsible held the view that it would otherwise devalue the regular three-litre formula for Grand Prix cars.
Upon the outbreak of World War II, all racing activities were discontinued.