Mercedes-Benz 300 SE (W 112), 1963 - 1965
Although Eugen Böhringer was able to crown the 1962 European Rally Championship season with the title for himself and Mercedes-Benz with the 220 SE – his first and the second after 1960 for the "Fintail" – the trends of the championship were clearly towards higher power-to-weight ratios for the participating vehicles. Compact two-door cars such as the Saab 96, Volvo 122 S, Ford Cortina GT and above all the revolutionary Mini Cooper were poised to take over the leading role in international rallying.
Naturally, Stuttgart wanted to continue the outstanding successes of the 220 SE Saloons and decided to remain clearly superior to the competition, at least in terms of engine performance and suspension qualities, while maintaining the same level of durability. Instead of the 220 SE, the top saloon among the "Fintail Mercedes" models, the significantly more powerful 300 SE (W 112), was to cause a sensation in the European Rally Championship in the new season and beyond.
While there were hardly any differences between the previous and the new vehicle on the outside – especially since most of the additional brightwork of the top model had been removed for weight reasons – there were plenty of changes under the sheet metal skin, which were partly due to the different specification of the production vehicle, but also specifically to the purpose of rally racing.
The heart of the 300 SE was undoubtedly its in-line six-cylinder M 189 with 3 litres of displacement. Although the basic design of the engine was already almost a decade old, it was anything but technically outdated with its cast aluminium crankcase, a seven bearing crankshaft as well as an overhead chain-driven camshaft and, of course, petrol injection. Although the engine was subject to certain limitations due to its design and hardly offered any more possibilities for far-reaching further development measures, it was nevertheless a reliable and powerful unit with which one could confidently meet the attacks of the new generation of vehicles in rallying.
Intensive fine-tuning of the moving parts of the six-cylinder engine and the use of petrol direct injection, which Mercedes-Benz had otherwise only used in the 300 SL (W 198) and 300 S (W 188), had ensured a significant output increase compared with the production vehicle. While the latter had to make do with 118 kW/160 hp in 1963, the rally version of the 3-litre engine provided around 140 kW/190 hp in its first year of racing.
The power transmission of the saloon was just as durable as the engine and therefore just as suitable for use in competition. In contrast to the production version, the 300 SE rally car was equipped exclusively with a mechanical 4-speed gearbox operated by a centre shifter console. It was much better suited to the requirements of rally racing than Mercedes' own automatic transmission installed in the production model, which was only replaced by the manual gearbox at special customer request. In the further course of its rallying career, the 300 SE also benefited from the installation of a 5-speed manual gearbox, which was even better matched to the performance characteristics of the six-cylinder engine.
With its unibody construction resting on an extremely robust frame floor system, the 300 SE withstood even the toughest stresses of rally racing. The same applied to the design of the wheel suspension. At the front, a double wishbone axle was used, which was equipped with air suspension bellows and external telescopic shock absorbers, as in the production vehicle. The air suspension offered the great advantage over conventional steel suspensions that the ground clearance of the body could be set lower or higher depending on the road conditions. A torsion bar stabiliser was used to limit roll in fast corners.
The rear suspension was the traditional Mercedes-Benz single-joint swing axle, which was also equipped with air suspension bellows and external telescopic shock absorbers. An additional steel compensating spring ensured that the saloon, which weighed almost 1500 kilograms despite the use of Plexiglas windows and a massively slimmed-down interior, could be controlled at all times, including at high speeds. Air suspension bellows and shock absorbers with firmer tuning were installed on the front and rear axle in line with the motorsport purpose.
The four-wheel disc brake system of the 300 SE rally car, on the other hand, corresponded to the production standard. If, depending on the operating conditions, not the standard 13-inch wheels were used here, but – as was sometimes the case – those with a diameter of 14 or 15 inches, the installation of a racing brake system from the British manufacturer Dunlop brought further deceleration reserves.
in 1963, the European Rally Championship comprised a total of six rounds, in which not only the 300 SE but also the previous year's 220 SE model was used. The 300 SE scored a first overall victory for Mercedes-Benz at the punishing Acropolis Rally driven by the crew of Böhringer/Knoll. There was another one to report in the Deutschland Rally, when the Böhringer/Kaiser team came out on top against their brand-mates Glemser/Baumgart in a 220 SE.
Overall, however, the season saw the more compact cars such as the Saab 96, Volvo 122 S, Mini Cooper and Alfa Romeo Giulia SZ finish in the top positions in the majority of European Championship races. Despite some remarkable results the next year as well, the time in which large four-door saloons had been able to win laurels in rallying was inexorably running out. However, in endurance races advertised for touring cars, such as the 24 Hours of Spa-Francorchamps or the 6 Hours of Nürburgring, the 300 SE remained a very successful competitor, taking overall victory in both events in 1964, as well as in the Macau Grand Prix.
Even more spectacular were the impressive successes that the 300 SE brought to the Mercedes-Benz team in Argentina. In the 1963 Argentine Touring Car Grand Prix, the 300 SE models finished 1st, 2nd and 4th (with a 220 SE in 3rd place) and scored a one-two-three the following year. Mercedes-Benz was thus able to score four consecutive victories in this extremely gruelling long-distance race covering more than 4500 km: In 1961 and 1962 with the 220 SE, in 1963 and 1964 with the 300 SE.