After their disastrous 1936 season, Mercedes-Benz appointed 30-year-old Rudolf Uhlenhaut as their Technical Director. In common with Auto Union, Mercedes had stuck to the same basic design of their GP car throughout 1934-36, but whereas the Auto Union developed into the superb C-type, the W25 Mercedes became a failure.
Over the winter, Uhlenhaut drove the cars himself at the Nurburgring to find out what was wrong with them. He then produced the magnificentWI25 for 1937, a car that was destined to become an icon of grand prix racing.
Uhlenhaut put a 5.6-litre, 580bhp version of the W25’s supercharged, straight-eight engine into an oval tubular chassis which was suspended by wishbones and coil springs at the front and de Dion at the rear.
Driven by Hermann Lang, this car won first time out, at Tripoli and, after being humiliated by Auto Union in 1936, Mercedes were back!
The next event was the Avus GP and for this Mercedes built three streamlined bodies, based on the car with which Rudi Caracciola had set those records in October, 1936:The very high speeds expected on the six-mile straights at Avus had Mercedes and Auto Union worried about tyres, so they hedged their bets and entered streamlined and unstreamlined cars, all using enormous 24-inch wheels at the rear. Both teams equipped their streamliners with built-in, compressed air jacking systems.
Mercedes entered two eight-cylinder streamliners for Caracciola and Lang and a 12-cylinder for von Brauchitsch. Caracciola was given a slightly lengthenedW(VVagen)125; Lang had a I936W25 powered by an M(Motor)I25 engine and von Brauchitsch had Caracciola’s record-breaker,fitted with the new, streamlined bodywork and powered by the DAB engine.
Two open-wheel cars were prepared, a normal W125 for Dick Seaman and a I 936W25 chassis fitted with a DAB I 2-cylinder power plant for Goffredo Zehender. Unfortunately, he blew it up in practice and did not take part in the race.
The streamliners were tested in the Zeppelin wind tunnel at Friedrichshafan and achieved a drag coefficient of 0.235, yet the less powerful Auto Unions were undoubtedly as fast, if not faster, than the Mercedes at Avus.
This aerodynamic superiority was proved conclusively throughout the Rekordwoche in October, when Auto Union set 16 new records and Mercedes-Benz were forced to return home empty-handed, foiled by frontend lift — a problem that gave Lang the fright of his life at Avus (see main text).