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.

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.

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.

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.