Mercedes-Benz W 25 record car, 1934
After the last race of the newly developed W 25 racing car in the 750 kg Formula at the end of September on the Masaryk Circuit near Brno, where Rudolf Caracciola had achieved a second place, Untertürkheim was able to look back on a successful 1934 racing season. Although the W 25 had initially had to contend with a few teething troubles, the company had been able to clearly win the contest against domestic competitor Auto Union from Zwickau, which had appeared on the scene since the end of May with its V16 mid-engined racing car designed by Ferdinand Porsche.
A different situation arose with the subject of record-breaking runs, which had disappeared from the headlines in Germany for over two decades after the spectacular world land speed record set by the so-called "Blitzen-Benz" in Daytona Beach in the USA in April 1911. Here, Auto Union factory driver Hans Stuck had surprisingly set several international records on Berlin's AVUS in March 1934 with one of the mid-engined cars that was still untested in races and not even specially prepared.
Not without reason, this clever PR manoeuvre launched before the start of the season was understood in Untertürkheim as a clear challenge. In the end, it took more than half a year for Daimler-Benz to take up the gauntlet and let two of the now fully developed W 25s chase the record in slightly modified form. The scene was a newly built, dead-straight stretch of concrete road near Gyón, a small town south of the Hungarian capital Budapest. Here, Rudolf Caracciola took up the challenge of setting new speed records with standing and flying starts on 28 October 1934.
The two cars were equipped with the inline eight-cylinder engine of the M 25 B evolutionary stage, which was equipped with a Roots blower and two hermetically sealed carburettors and delivered a peak output of 430 hp/316 kW with a displacement of just under four litres - 135 hp/99 kW more than the large-volume, lower-revving V16 of Auto Union had produced at the beginning of the year.
The modifications focused on aerodynamic improvements and weight-saving measures. Due to the considerably reduced need for cooling air compared to racing, the corresponding opening at the front of the car was significantly reduced in size in the interest of optimal aerodynamics. At the same time, the ventilation slots in the side of the engine cover disappeared. Instead, a small single opening was provided on both sides, through which the engine heat could escape.
The highlight, however, was that one of the W 25s was equipped with a cockpit canopy that could be opened forwards for the runs with a flying start, where the highest speeds had to be achieved. In contrast, the second car was still open and intended for driving with a standing start. It had a raised front cockpit cut-out instead of the small racing windscreen, which enabled the air to flow better over the driver. Due to the lack of any need for braking power, and for weight-saving reasons, front wheel brakes were dispensed with on both cars.
The record-breaking runs in Gyón ended in complete success for Daimler-Benz. Caracciola achieved two international records with a flying start in the closed W 25, which he slightly coyly referred to as a "racing saloon": in Class C (vehicles with engines of 3 to 5 litres displacement), he achieved speeds of 317.5 km/h and 316.6 km/h over one kilometre and one mile respectively. With a standing start, he even managed to set a new world record over one mile with a speed of 188.6 km/h.
A few weeks later, in December 1934, the closed W 25 showed some minor changes on the occasion of new record runs on the AVUS. The engine cover now featured the usual racing car ventilation slots, while the cockpit canopy had a flattened roofline and a wider, central windscreen that offered better sightlines. In addition, narrow ventilation slots were incorporated below the two forward-curved side windows, which improved the pressure conditions in the tight, narrow cockpit. To reduce air turbulence as much as possible, the wire spokes of each rear wheel were covered with a disc as an additional detail.
In this form, the "racing saloon" set another international record in Class C under Caracciola: the new benchmark over five kilometres with a flying start was set at 311.98 km/h.
As was to become apparent in the following years, however, these were only preliminary skirmishes for a dogged duel for ever new records, fuelled with gusto by the National Socialist rulers, the outcome of which reverberates to the present day.