Mercedes-Benz W 25 (1934 to 1936)

Aug 20, 2012
  • The vehicle that gave rise to the name “Silver Arrow”
  • Over three years of motor racing success for the brand
  • Record-breaking version for high-speed runs
High unemployment and an economic crisis, the Mercedes-Benz works racing department closed: 1932 did not seem to offer a very favourable backdrop for motorsport activities in Germany. But there was at least some hope for the future, for that autumn the motor sport association AIACR (Association Internationale des Automobile Clubs Reconnus) in Paris announced a new formula for Grand Prix racing, formulated in 1932 and due to come into effect in 1934: the cars, without fuel, oil, coolant, and without tyres should weigh no more than 750 kilograms, but otherwise the engineers were not subject to any further restrictions. In the light of today’s racing formulae, which demand a minimum weight, a maximum weight limitation might appear strange, but with the 750 kilogram formula the AIACR was aiming to restrict the speed of racing cars compared with the models of the previous generation. The assumption was that a light vehicle would necessarily be fitted with a smaller engine with a low output. But the powers that be had underestimated technological progress: during the lifetime of the 750-kilogram formula from 1934 until 1937 alone, the engine output of the Mercedes-Benz racing cars was more than doubled.
The decision that the company would develop its own racing car was finally reached at Mercedes-Benz in 1933 – racing manager Alfred Neubauer’s persistence in appealing for a return to racing having finally met with success. However, with the seizing of power by the National Socialists, the conditions for motorsport in Germany had also changed: the NS regime was very keen to promote the automotive economy, appropriated responsibility for existing autobahn construction projects, reduced taxes on new vehicles and encouraged the leading manufacturers to get involved with motor sport. And so it was that a new rival to Mercedes-Benz appeared on the scene: Auto Union, with its headquarters in Chemnitz, was created in August 1932 as the result of a merger between the state of Saxony’s four vehicle manufacturers Audi, DKW, Horch, and Wanderer. Rivalry between racing cars bearing the three-pointed star and those bearing the four rings of Auto Union would go on to define European motor racing in the years up until 1939.
Once the decision to go ahead with the racing car with the designated number W 25 had been made, Alfred Neubauer immediately began to put together a racing team. One of the drivers that heapproached was Rudolf Caracciola, although after sustaining serious leg injuries in an accident in Monaco in April 1933 and having to spend several months in hospital, it was still not clear whether the latter would be fully fit again in time. The team also included the drivers Manfred von Brauchitsch, Luigi Fagioli, Hanns Geier, and Ernst Henne.
New racing car an absolute winner
The engineers around Hans Nibel, Chief Engineer at Board level, worked under considerable time pressure to develop a new racing car. The layout, with a front engine, was actually rather conservative compared with Auto Union’s mid-engined car or with earlier developments by the company’s own brands, such as the Benz “Teardrop” car. Nevertheless, the combination of a slim body, a mechanically supercharged 3.4-litre in-line eight-cylinder engine, individual wheel suspension and a transmission mounted directly on the rear axle, all added up to make the car an absolute winner. Responsible for the chassis at Daimler-Benz was Max Wagner, with the duo of Albert Heess and Otto Schilling working on the engine. In the testing department headed up by Fritz Nallinger, Georg Scheerer, one of those who had been there since the very early days of the supercharged “Kompressor” models built by the Daimler-Motoren-Gesellschaft (DMG), was responsible for putting the engines very thoroughly through their paces. Otto Weber would assemble them, while Jakob Kraus took over the fitting of the chassis. By the winter of 1933 Neubauer was already waxing lyrical about the elegant monoposto that would once again take his team to victory.
In 1934, the first test drives with the new racing car took place from February onwards in Monza as well as on the motorway between Milan and Varese. With 320 hp (235 kW) – subsequently 354 hp/260 kW with a new blend of fuel – the car reached top speeds of more than 250 km/h.
With the advent of the W 25, Mercedes-Benz also introduced a new colour for the bodywork: silver. The car’s first appearance should have been at the Avus race in Berlin in May 1934, but participation was cancelled at the last minute due to technical problems. And so it was that the new car did not make its debut until a week later, on 3 June at the International Eifel race on the Nürburgring. The W 25 went to the starting line in silver livery – so the story goes – after the racing cars were stripped of their white paint at the Nürburgring to reduce weight. Although this race was not held according to the new 750-kilogram formula, the team were clearly keen to present a vehicle that already met the new rules. The term “Silver Arrow” was not coined until later, but would become increasingly popular over the years.
First start and first victory – the beginning of a legend
The Eifel race of 1934 marked the first start and at the same time the first victory for the new Mercedes-Benz formula racing car. Manfred von Brauchitsch drove the W 25 to the chequered line at an average speed of 122.5 km/h – setting a new record for the circuit in the process.
Further victories in the first year of the W 25 included Rudolf Caracciola winning the Klausen race in Switzerland, Luigi Fagioli’s triumph in the Coppa Acerbo at Pescara and victory in the Italian Grand Prix in Monza. With a total of around 1,300 bends and chicanes to be negotiated, Monza was the most difficult fixture of the 1934 racing season. Rudolf Caracciola was still not fit enough after his accident to get through the whole race and was in considerable pain. Halfway through the race his place at the wheel of the car with the starting number 2 was therefore taken by Luigi Fagioli. The Italian, whose own car had been retired early with technical problems, was able to defend the advantage built up by Caracciola right to the finishing line. At the Spanish Grand Prix the Mercedes-Benz racing team won once again and took their first double victory, with Luigi Fagioli winning ahead of Rudolf Caracciola. Fagioli then finished second in the Masaryk Grand Prix in Brno.
1935: season dominated almost completely by Mercedes-Benz
Mercedes-Benz was thus once again back at the forefront of international motor racing. After the 1934 season this could no longer be doubted. The Stuttgart team responded to the successes of their strong rivals from Auto Union in the 1935 season by making various further improvements to the W 25. The most powerful engine – M 25 C – now produced an output of 494 hp (363 kW) at 5800 rpm from a displacement of 4310 cubic centimetres. This was the car with which Mercedes-Benz would almost completely dominate the 1935 racing season. Rudolf Caracciola was back on top form and won the Tripoli Grand Prix, the Eifel race, the French Grand Prix, the Belgian Grand Prix, the Swiss Grand Prix, and the Spanish Grand Prix. The lead driver for the Silver Arrows was thus given the title of European Champion, awarded that year for the first time. To add to these successes, in 1935 Luigi Fagioli also won the Monaco Grand Prix, the Avus race, and the Barcelona Grand Prix (ahead of Caracciola).
The 449 hp (330 kW) W 25 of 1936, which had a shorter wheelbase compared with its predecessors, could however not match this string of successes. In that year Mercedes-Benz won only the Monaco and Tunis Grands Prix, both with Caracciola at the wheel.
Mercedes-Benz W 25
Years of construction:
1934 to 1936
8, in-line
up to 4,740 cc
up to 494 hp (363 kW)
Top speed:
approx. 300 km/h
Start of the International Eifel Race at the Nürburgring, 3 June 1934. Manfred von Brauchitsch won the race in a Mercedes-Benz W 25 racing car weighing just 750 kilograms, used for the first time in a race.
Start of the Monaco Grand Prix, April 22,  1935. Threei Mercedes-Benz formula racing cars  W 25 in the startin line. start number 4 - Luigi Fagioli, the winner. start number 6 - Manfred von Brauchitsch. start number 2 - Rudolf Caracciola.
Rudolf Caracciola is crowned the 1935 European Grand Prix Champion at the wheel of the Mercedes-Benz W 25 formula racing car, which weighed a mere 750 kilograms. He claimed victories at races including the French Grand Prix in Montlhéry, on 23 June 1935, ahead of his team mate Manfred von Brauchitsch.
Rudolf Caracciola is crowned the 1935 European Grand Prix Champion at the wheel of the Mercedes-Benz W 25 formula racing car, which weighed a mere 750 kilograms. The photograph shows the subsequent winner Caracciola at the international “Eifelrennen” race at Nürburgring on 16 June 1935.
Rudolf Caracciola is crowned the 1935 European Grand Prix Champion at the wheel of the Mercedes-Benz W 25 formula racing car, which weighed a mere 750 kilograms. He won the Belgian Grand Prix in Spa-Francorchamps on 14 July 1935.
Mercedes-Benz 750-kilogram W 25 racing car, built in 1934. Used for the first time at the International Eifel race on the Nürburgring on 3 June 1934 – the race was won by Mercedes-Benz racing driver Manfred von Brauchitsch.
Mercedes-Benz 750-kilogram W 25 racing car, built in 1934. Used for the first time at the International Eifel race on the Nürburgring on 3 June 1934 – the race was won by Mercedes-Benz racing driver Manfred von Brauchitsch.
International Eifel race, 3 June 1934. From the start, the two Mercedes-Benz 750-kilogram W 25 racing cars with Manfred von Brauchitsch (first place) and Luigi Fagioli at the wheel immediately took the lead. This was the racing premiere of the W 25.