The Mercedes-Benz Silver Arrows from 1934 to 1939

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Mercedes-Benz W 25 formula racing car from the year 1934.

  • 1934: a new star is born – the Mercedes-Benz W 25
  • W 125, W 154, and W 165 follow between then and 1939
  • Circuit races and speed records

On 3 June 1934, the new Mercedes-Benz W 25 Grand Prix racing car won in its debut race – the international “Eifelrennen”, or Eifel race, at the Nürburgring. This thrilling first victory marked the beginning of a glorious era for European motor sport.

The W 25 of 1934 and the vehicles that followed it left their lasting mark on that era. And the fascination exuded by the Mercedes-Benz racing cars in their silver paintwork remains undiminished to this day, giving them an appeal that is as strong as ever. An appeal that is felt, for example, whenever Mercedes-Benz Classic puts in an appearance at the key events of the international classic racing calendar and uses these occasions to show the cars in their full racing glory. The vehicles from the 1930s continue to delight spectators at today’s events as much as they ever did in the past.

“These are original vehicles of the very highest quality: every Silver Arrow in the company’s collection is authentic down to the last detail and, what is more, has an individual racing history of its own,” says Michael Bock, Head of Mercedes-Benz Classic. “So these vehicles, at the same time, provide evidence of the high standards set by Mercedes-Benz Classic in terms of the authenticity of classic vehicles. Authenticity is the principle behind every piece of work that Mercedes-Benz Classic takes on – and one that is probably more rigorously applied than any other manufacturer is capable of doing. Only genuinely original vehicles can truly convey authentic history and authentic stories.”

The Silver Arrows dominate motor racing

Their speed, together with their paintwork in the colour of bare aluminium, led to the W 25 and its successors, the W 125, W 154, and the W 165 Tripoli car, becoming known quite simply as the Silver Arrows. Until 1939 they continued to dominate European motor racing at all the major fixtures: the Mercedes-Benz Silver Arrows won three European Championships, the equivalent of today’s Formula 1 World Championship title. On top of these came numerous other victories and sensational records.

To create the racing cars with which the motor racing department in Stuttgart was able to deliver victory upon victory for the company, the engineers combined innovative new engineering design with existing cutting-edge technology from Mercedes-Benz, further developing these in a process of skilful and constant further development. They were thus able to build successful competitive vehicles that would also continue to be improved over the course of the particular season.

The Silver Arrows became legends even in their own time. They continued to add to the list of successes that Mercedes-Benz and the company’s founder brands had consistently achieved since the very first days of motorsport in 1894. And after the Second World War, in the 1950s, it was the tradition of the W 25 and W 165 models that once again provided the basis for the development of a second and equally successful generation of Silver Arrows in the form of the W 196 Grand Prix racing car and the 300 SLR racing sports car.

The directors, the engineers and the workers of the racing department with the new Mercedes-Benz W 25 750-kg formula racing car, February 1934.

The directors, the engineers and the workers of the racing department with the new Mercedes-Benz W 25 750-kg formula racing car, February 1934.

Mercedes-Benz W 25 (1934 to 1936)

  • 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.Mercedes-Benz W 25 formula racing car, 1936 version: Small air intakes in the front mask and completely covered suspension arms on the rear axle.

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.

Mercedes-Benz W 25 formula racing car, 1936 version: Small air intakes in the front mask and completely covered suspension arms on the rear axle.

Mercedes-Benz W 25 formula racing car, 1936 version: Small air intakes in the front mask and completely covered suspension arms on the rear axle.

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.

Mercedes-Benz W 25 formula racing car, 1936 version: Small air intakes in the front mask and completely covered suspension arms on the rear axle.

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
Cylinders: 8, in-line
Displacement: up to 4,740 cc
Output: up to 494 hp (363 kW)
Top speed: approx. 300 km/h

The superior car of the 1937 season: The Mercedes-Benz W 125 formula racing car.

The superior car of the 1937 season: The Mercedes-Benz W 125 formula racing car.

Mercedes-Benz W 125 (1937)

  • Dominant vehicle of the 1937 season
  • Completely redesigned racing car
  • Engine output of more than 600 hp (441 kW)

In the wake of the disappointing performance of the modified W 25 in its third season (1936), Mercedes-Benz developed a new vehicle specifically for the last year of racing under the formula that was to be discontinued in 1937. Rudolf Caracciola’s record-breaking attempts during the winter of 1936 had already given an indication of the potential for innovation within the Stuttgart racing department. That November and December, on the new autobahn (motorway) between Frankfurt and Darmstadt and in the Mercedes-Benz twelve-cylinder streamlined record-breaking model, Caracciola set five international class records and one world record. In doing so he also beat by a considerable margin the figures achieved in the same spot just a few months earlier, in March that year, by Hans Stuck in an Auto Union car.

Mercedes-Benz W 125.

Mercedes-Benz W 125.

The year 1937 was dominated by the new W 125 with an eight-cylinder engine and mechanical supercharger, which produced a top performance of around 600 hp (441 kW) from a displacement of 5.6 litres. The W 125 was designed by a young engineer, just 30 years of age, who had been put in charge of the newly created racing department in the middle of 1936: Rudolf Uhlenhaut. He not only developed new design concepts, but also tested the racing cars himself – he was a talented driver and often just as fast as the drivers who were officially on the payroll. Thanks to him, Mercedes-Benz was once again able to take its place at the forefront of European motor racing. Uhlenhaut was a man who focused on delivering detailed technical solutions. For the first time on a Silver Arrow, the supercharger was fitted downstream of the carburettors – with the effect that the turbocharger was actually compressing the final mixture. This in-line eight-cylinder engine represents the most advanced stage of development reached by the Grand Prix engine that had been in service since 1934.

The backbone of the vehicle was formed by an extraordinarily robust tubular frame made out of a special steel alloy and characterised by its four cross-members and elliptical cross-section. The wheels at the front were controlled by double-wishbone steering with coil springs. At the back, a De Dion double-jointed axle with lengthwise-mounted torsion bar springs and hydraulic lever-type shock absorbers ensured constant camber. Lateral control arms were used to pass the acceleration and braking torque through to the chassis.

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Mercedes-Benz formula racing car W 125, 1937 (on the test track in Untertürkheim, 1972).

Upside down world for the suspension of the W 125

After extensive test drives on the Nürburgring circuit, Rudolf Uhlenhaut opted for a revolutionary chassis design. He replaced the hitherto customary principle of hard springs and minimal damping with the complete opposite. The W 125 featured a soft-sprung suspension, with extremely long shock courses for the springs, complemented by a high level of damping, so establishing the pattern for Mercedes-Benz sports cars even today. In exterior appearance it was very similar to its predecessor. What made the W 125 unmistakable, however, were the three cooling vents in its front section. The W 125 had open wheels: the car was only fitted with a streamlined body for the very fast Avus race on 30 May 1937.

Victory followed victory in the 1937 racing season: Hermann Lang won the Tripoli Grand Prix as well as the Avus race, on that occasion in the aerodynamically optimised W 125. His average speed in this race of 271.7 km/h was not surpassed until 1959. In the Eifel race, Caracciola and von Brauchitsch finished second and third respectively, while Caracciola won the German Grand Prix, also ahead of von Brauchitsch. Manfred von Brauchitsch went on to win the Monaco Grand Prix, with Caracciola and Christian Kautz as well as Goffredo Zehender (5th) close behind him. At the Swiss Grand Prix the winners’ podium was occupied by Caracciola, Lang, and von Brauchitsch, while victory in the Italian Grand Prix was claimed by Caracciola ahead of Lang. The record year was then rounded off at the Masaryk Grand Prix in Brno, won by Caracciola with von Brauchitsch in second place. Despite his best efforts, Bernd Rosemeyer was only able to win four races in the Auto Union car. The superiority of the Mercedes-Benz team was underlined by the fact that its drivers took the first four places in the European Championship: Caracciola followed by von Brauchitsch, Lang, and the Swiss driver Christian Kautz. The year 1937 marked a high point for Mercedes-Benz, but also brought the end of the 750-kilogram formula. A new regulation would come into force from 1938.

Mercedes-Benz W 125
Year of construction: 1937
Cylinders: 8, in-line
Displacement: 5,663 cc
Output: 592 hp (435 kW)
Top speed: over 320 km/h

Triple victory in the Tripoli Grand Prix, May 15, 1938: Hermann Lang (photo) ahead of Manfred von Brauchitsch and Rudolf Caracciola, all driving Mercedes-Benz W 154 cars.

Triple victory in the Tripoli Grand Prix, May 15, 1938: Hermann Lang (photo) ahead of Manfred von Brauchitsch and Rudolf Caracciola, all driving Mercedes-Benz W 154 cars.

Mercedes-Benz W 154 (1938 to 1939)

  • Vehicle surpasses excellent performance of its predecessor at a stroke
  • New mix of outstanding technical components takes it straight to the head of the field

In September 1936, the motor racing association AIACR announced details of the new Grand Prix formula that would take effect from 1938. The key points: a maximum displacement of 3 litres for supercharged engines or 4.5 litres for naturally aspirated engines; and a weight of at least 400 and at most 850 kilograms, depending on the displacement. These requirements made necessary the development of a completely new vehicle. The 1937 season was still in full swing as work began at Mercedes-Benz to develop the car for the following year’s racing.

There was certainly no shortage of ideas from the racing design engineers: they considered the idea of a W 24 naturally aspirated engine with three banks of eight cylinders each, as also of a rear-positioned engine, direct petrol injection and a fully streamlined body. In the end, primarily in order to manage the thermal conditions, the engineers opted for a V12 with a V-angle of 60 degrees, developed in-house by Daimler-Benz specialist engineer Albert Heess. The cylinders were combined in groups of three in welded-on steel plate cooling jackets with non-removable heads. Powerful pumps propelled 100 litres of oil per minute through the engine, which weighed around 260 kilograms. Compression was provided initially by two single-stage superchargers, which were replaced in 1939 with a single two-stage unit.

Racing car with well-balanced weight distribution: Mercedes-Benz W 154 of 1938.

Racing car with well-balanced weight distribution: Mercedes-Benz W 154 of 1938.

By January 1938, the engine was being tested on the test bench. The first completely trouble-free test took place on 7 February, during which it delivered 427 hp (314 kW) at 8000 rpm. For the first half of the season the drivers had an average of 430 hp (316 kW) at their disposal, which by the end of the season had climbed to more than 468 hp (344 kW). The most powerful version of the engine, with 483 hp (355 kW), was used by Hermann Lang at the French Grand Prix in Reims. This was also the first Mercedes-Benz racing car to feature a five-speed transmission.

Chassis engineer Max Wagner had a much easier job of it than his colleagues on the engine development side. He was able to adopt the advanced chassis architecture of the W 125 from the previous year virtually unchanged, although he did take the opportunity to improve the torsional rigidity of the frame by a further 30 per cent. The V12 engine was set very low, with the air intakes for the carburettors peeping out from behind the centre of the radiator grille; the grille itself became wider and wider as the beginning of the season approached. The driver sat on the left, next to the propshaft, with the overall result that the W 154 looked as though it was crouching low over the asphalt. In silhouette, the tops of the wheels appeared to stand higher than the contours of body. As well as enhancing the dynamic look of the car, this also significantly lowered the centre of gravity. The works drivers, whose experience technical boss Rudolf Uhlenhaut trusted implicitly, were immediately impressed by the road-holding qualities of the new racer W 154.

W 154 "Silver Arrows" on board: Mercedes-Benz racing transporters in the 1930s.

W 154 „Silver Arrows“ on board: Mercedes-Benz racing transporters in the 1930s.

Impressive dominance: one triple victory after another

The W 154 was indeed able to outshine the excellent performance set by its predecessors: this Silver Arrow gave the Mercedes-Benz racing department its greatest number of victories during this era. This first race of the 1938 season nevertheless ended in disappointment: on the twisting circuit in Pau, France, the car was unable to display its full potential and was set back by a refuelling stop. But things improved rapidly thereafter. The Tripoli Grand Prix resulted in a triple victory for Lang, von Brauchitsch, and Caracciola, a feat that was repeated at the French Grand Prix in the sequence von Brauchitsch, Caracciola, and Lang. The British driver Richard Seaman, who had joined the team in 1937, won the German Grand Prix on the Nürburgring ahead of the car driven jointly by Caracciola und Lang, while Hermann Lang went on to win the Coppa Ciano in Livorno and Rudolf Caracciola the Coppa Acerbo at Pescara. At the Swiss Grand Prix, the W 154 once again took the first three places (Caracciola, Seaman, and von Brauchitsch), while Rudolf Caracciola became European Champion for the third time. Auto Union, whose top driver Rosemeyer had been killed during the record-breaking attempts of January 1938, were only able to come through with a few successes towards the end of the season.

In 1939, the last season of racing before the Second World War, Mercedes-Benz was able to build further on the successes of the previous year with the W 154. The first race of the season was the Pau Grand Prix, which Hermann Lang won in a W 154 ahead of Manfred von Brauchitsch, so taking his revenge for the defeat of the previous year. In addition, Lang took the chequered flag at the Eifel race in May of the same year, with Caracciola in third place and von Brauchitsch in fourth.

Second World War prevents Caracciola from taking fourth European Championship title

Hermann Lang continued to build on this impressive series of victories. He won the Höhenstrassen-Rennen (High Road Race) in Vienna in a hillclimb version of the W 154 (with von Brauchitsch in 3rd place), a result replicated at the Belgian Grand Prix in Spa. Caracciola then won the German Grand Prix at the Nürburgring – for the fifth time. The Swiss Grand Prix was won by Lang ahead of Caracciola and von Brauchitsch. Lang also won the German Hillclimb Grand Prix on the Grossglockner pass, thereby securing the 1939 German Hillclimb title. He was clearly the season’s top driver, but with the outbreak of war the authorities responsible, the AIACR in Paris, were unable to award the title of European Champion.

The last start for the Silver Arrows in 1939 was in the second Belgrade City Race on 3 September. Manfred von Brauchitsch finished second in his W 154 behind Tazio Nuvolari for Auto Union. But by this time, the Second World War had already begun.

Mercedes-Benz W 154
Years of construction: 1938 to 1939
Cylinders: V12
Displacement: 2,962 cc
Output: up to 483 hp (355 kW)
Top speed: approx. 300 km/h

Mercedes-Benz Grand Prix racing car W 165 of 1939, winner car of the Grand Prix of Tripoli on 7 May 1939.

Mercedes-Benz Grand Prix racing car W 165 of 1939, winner car of the Grand Prix of Tripoli on 7 May 1939.

Mercedes-Benz W 165 (1939)

  • Specially designed for the Tripoli Grand Prix
  • Developed in a record time of just eight months
  • Double victory and thus mission accomplished

The Tripoli Grand Prix marked a notable exception among the Mercedes-Benz victories of 1939. The competition was not held according to the 3-litre formula dominated by the German racing cars, but according to the 1.5-litre category (voiturette formula), for which the Stuttgart team – up until then – did not have any entrants. With this trick, the Italian motor racing authorities responsible for organising the prestigious Tripoli Grand Prix in Libya – at that time an Italian colony – hoped to undermine the dominance of the Silver Arrows and ensure once and for all victory for the Italian cars. The Italians’ last win in this race had been back in 1934, since when the German cars had repeatedly triumphed on the Mellaha circuit: Caracciola had won in 1935 and Auto Union in 1936, while in 1937 and 1938 it had been taken by Hermann Lang at the wheel of the winning Mercedes-Benz.

Mercedes-Benz, however, was not to be so quickly deterred from competing in one of the most important races of the Grand Prix world of the 1930s. From when the new regulations were issued, in September 1938, the Stuttgart team proceeded to take less than eight months to develop a completely new racing car: the W 165. The key drawings were soon provided by engine specialist Albert Heess and chassis expert Max Wagner, so that the first vehicle was ready to be tested by Caracciola and Lang at Hockenheim as early as April 1939. It was therefore with considerable astonishment that the international racing world saw two Mercedes-Benz W 165 cars with a displacement of 1.5 litres appear in the list of contenders for the Gran Premio di Tripoli.

Tripoli Grand Prix, May 7, 1939: Hermann Lang won the race at the wheel of the Mercedes-Benz W 165 racing car.

Tripoli Grand Prix, May 7, 1939: Hermann Lang won the race at the wheel of the Mercedes-Benz W 165 racing car.

The new racing car bore a distinct similarity to the existing W 154 racing car but appeared, at first glance, to be a scaled-down version of the 3-litre racer. The struts of its oval tubular frame were made out of nickel-chrome-molybdenum steel, with the five cross-members supplemented by the rear engine bracket. The driver did not sit in the middle, but slightly to the right. With a full fuel tank the W 165 weighed just 905 kilograms. The engine too, even though it weighed just 166 kilograms, was clearly a close relation of the V12 engine from the W 154. It was a V8 engine with a displacement of 1493 cc, a V-angle of 90 degrees and with four overhead camshafts and 32 valves, with an almost identical arrangement and drive system to those in the Grand Prix model. The mixture was prepared by two Solex suction carburettors, with powerful support from two Roots blowers. Its output of 254 hp (187 kW) at 8000 rpm equated to a power-to-swept volume ratio of 170 hp (125 kW) – an absolute record figure. This power was tamed by large brake drums (360 millimetres in diameter), that almost filled the whole inside part of the spoked wheels. The engineers even allowed for the extreme temperatures to be expected in the host country – on race day the temperature on the track would be 52 degrees Celsius – by running the fuel pipes through tubular coolers.

The rest is racing history: the two Mercedes-Benz W 165s left their opponents no chance. Caracciola, in his shorter-ratio vehicle, completed the entire race without a break, while Hermann Lang – in line with Neubauer’s carefully devised tactics – made a brief pit stop to change tyres and won the Tripoli race in his longer-ratio vehicle (which thus had a higher maximum speed) almost a full lap ahead of his fellow Mercedes driver. A historic victory.

Mercedes-Benz W 165
Year of construction: 1939
Cylinders: V8
Displacement: 1,493 cc
Output: 254 hp (187 kW)
Top speed: 272 km/h

Optimized in the wind tunnel: Mercedes-Benz W 125 record car with twelve-cylinder engine, 1938.

Optimized in the wind tunnel: Mercedes-Benz W 125 record car with twelve-cylinder engine, 1938.

Record-breaking runs with the Silver Arrows

  • New realms of speed reached with special vehicle variants
  • Still unrivalled today: 432.7 km/h achieved by the W 125 on public roads in 1938

Attempts to break speed records were all part of the programme in the 1930s, as a way of demonstrating the performance and capability of both vehicles and drivers. Mercedes-Benz would regularly put several vehicles to the test against its rivals as they vied with each other to set new speed records.

As speeds increased, the silver racers found that the available tracks no longer met their needs. Whereas in 1934 a smooth, straight stretch of concrete near the Hungarian city of Györ, not far from Budapest, or the Avus circuit in Berlin, had been just about adequate, by 1936 the favoured length of road had become the Frankfurt–Darmstadt motorway (these days the German A 5 Autobahn/federal motorway). Finally, for the last record-breaking attempts before the outbreak of the Second World War, an unusually wide section of the new Dessau–Bitterfeld motorway was used.

Rudolf Caracciola further underscored the impressive performance of the W 25 Grand Prix racer in 1934 at Györ, near Budapest, in a vehicle with a fully enclosed cockpit – which he nicknamed affectionately his “racing saloon” – on a concrete track: with speeds of 317.5 km/h and 316.6 km/h he set international speed records for a Class C vehicle (displacement of between 3 and 5 litres) over a kilometre and a mile respectively from a flying start, and a new world record of 188.6 km/h over a mile from a standing start. The record-breaking run in Hungary was Mercedes-Benz’s retaliation for the one-hour record set by Auto Union in 1934 and marked the beginning of a rivalry for speed records that went on for many years – and was ultimately won by Caracciola in a Mercedes-Benz. On the Avus circuit in December 1934, Caracciola took the W 25 to an international class record for a Class C vehicle with a speed of 311.9 km/h over 5 kilometres.

Called‚ racing sedan‚ by Rudolf Caracciola: The Mercedes-Benz W 25 record car, 1934.

Called‚ racing sedan‚ by Rudolf Caracciola: The Mercedes-Benz W 25 record car, 1934.

Fully streamlined body developed by Zeppelin

The record-breaking car of 1936 was also based on the chassis of the W 25 but here, for the first time, was fitted with a fully streamlined body that also enclosed the wheels and the underbody. Developed in the wind tunnel of the Zeppelin works at Friedrichshafen, the light-alloy construction weighed around 100 kilograms, so allowing it to achieve the sensational drag coefficient, or cd value, of 0.235. Power came courtesy of a V12 engine (MD 25 DAB/1) with an output of 616 hp (453 kW) from a displacement of 5577 cc. This had originally been designed for use in Grand Prix racing, but proved to be too heavy. With this engine, Caracciola was able to set several records for a Class B vehicle, for example with a world record of 333.5 km/h over 10 miles from a standing start. The top speed achieved over this distance was 372 km/h.

The race for ever higher speeds continued. Having long recognised the prestige value of record-breaking drives, the Supreme National Sports Authority in Germany (ONS) organised an international record week on the Frankfurt–Darmstadt autobahn, although in fact almost all participating vehicles were German. It ended in a clear triumph for Auto Union, with Bernd Rosemeyer establishing a string of new top speeds, including becoming the first driver to go above 400 km/h on a public road. By contrast, the Mercedes-Benz cars performed disappointingly and were recalled prematurely to the factory. But in January 1938, ahead of the Berlin Motor Show, the company’s management succeeded in arranging for another series of record-breaking attempts to be made on the same stretch of road. Rudolf Caracciola, in a significantly improved vehicle, set another new speed record – one which still stands to this day. In the twelve-cylinder record car based on the W 125 he reached the fastest speed ever recorded on a public road: 432.7 km/h for the kilometre from a flying start and 432.4 km/h for the mile from a flying start. In an attempt to trump this record immediately, Auto Union’s star driver Bernd Rosemeyer was killed when his vehicle, travelling at full speed, was caught by a gust of wind and thrown off the road.

Another record: drag coefficient of just cd = 0.157

The record-breaking version of the W 125 was – like all the other Mercedes-Benz record cars of this era – meticulously prepared for its special role in the wind tunnel of the Deutsche Versuchsanstalt für Luftfahrt (German Institute for Aviation Research) in Berlin-Adlershof. With a cd value of just 0.157 it was on target to set records. The car was powered by the latest evolutionary stage of the 5.6-liter twelve-cylinder engine. Two Roots blowers boosted its output to 736 hp (541 kW) at 5800 rpm. A preliminary version of the 6.25-meter-long record vehicle tended to loose ground contact at 400 km/h. Rudolf Uhlenhaut therefore reduced the frontal area to a minimum, as a way of reducing the radiator’s flow resistance. Just two small nostrils supplied intake air to the huge V12. Optimal working temperatures over the short distances in question were looked after by the conventional radiator of the W 125, embedded in a chest filled with half a cubic meter of ice and water and resting on two supports in front of the engine.

By 1939 specialisation had made such advances that the then current model W 154 could be used this time as the basis for two record-breaking versions for Class D (two to three litres displacement): one car for the flying start records and another variant, with wheel fairings and a characteristically notched section in the cockpit, for the standing sprint. Constant factors in all this remained the similarity between the engineering design of this car and that of the corresponding Grand Prix vehicle, and the choice of driver: the man taking responsibility for these records would once again be Rudolf Caracciola.

Record run on the Dessau‚ Bitterfeld motorway, February 9, 1939: Rudolf Caracciola in the Mercedes-Benz W 154 with twelve-cylinder engine (version for standing-start attempts).

Record run on the Dessau‚ Bitterfeld motorway, February 9, 1939: Rudolf Caracciola in the Mercedes-Benz W 154 with twelve-cylinder engine (version for standing-start attempts).

Streamlined three-axle model denied an appearance

The W 154 record car of 1939 had an output of 468 hp (344 kW) at 7800 rpm. The last record-breaking attempts of this nature on the motorway were also made with this car, in February 1939. For the flying start distances the car appeared with a futuristic-looking fully streamlined body, while for the standing starts the wheels were fitted with individual fairings. Caracciola set the following international class records for Class D (displacement of between 2 and 3 litres) in the Mercedes-Benz W 154 record car: over a kilometre from a standing start he reached 175.1 km/h, over a mile from a standing start 204.6 km/h; he then managed 398.2 km/h over a kilometre with a flying start and 399.6 km/h for the flying-start mile.

The 8.24-metre-long, three-axle T 80 record-breaking vehicle of 1939 was the car with which Mercedes-Benz ultimately aimed to break the world land speed record. By that time, a duel between the British drivers George Eyston and John Cobb on salt flats in Utah, USA, had driven this up to 595 km/h. This mighty vehicle was to be powered by the 807-kilogram DB 603 RS aircraft engine, a V12 unit that produced an impressive 3500 hp (2574 kW) from a displacement of 44,500 cc at 3640 rpm. As it was, though, the outbreak of the Second World War meant that the T 80 never got the chance to perform. It now, along with many of the other record-breaking vehicles from the 1930s, forms part of the Mercedes-Benz Classic vehicle collection and has found a home in the Mercedes-Benz Museum, where it can be admired and wondered at to this day.

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