The racing career of Herrmann, who is a baker by trade, spans from cooperation with pre-war legends like Alfred Neubauer to the beginning of the dominance of Porsche at the 24 Hours of Le Mans.

He took part in now legendary road races like Mille Miglia, Targa Florio and Carrera Panamericana and is one of the few remaining witnesses of this era.

Herrmann had a remarkable Mille Miglia race in 1954, when the gates of a railroad crossing were lowered in the last moment before the fast train to Rome passed.

Driving a very low Porsche 550 Spyder, Herrmann decided it was too late for a brake attempt anyway, knocked on the back of the helmet of his navigator Herbert Linge to make him duck, and they barely passed below the gates and before the train, to the surprise of the spectators.

From 1954 to 1955, he was part of the Mercedes-Benz factory team, as a junior driver behind Juan Manuel Fangio, Karl Kling, Hermann Lang and later Stirling Moss.

When the Silver Arrows came back for the 1954 French Grand Prix to score a 1–2 win, Herrmann drove the fastest lap but had to retire.

In the 1955 Argentine Grand Prix his teammates Kling and Moss had to abandon early due to the extremely hot conditions on the southern hemisphere in January.

He left Porsche at the beginning of the 1962 season feeling that he as a local from Stuttgart was No Prophet In His Own Land compared to Californian Dan Gurney and Jo Bonnier from Sweden.

Having witnessed fatal accidents of colleagues too many times, e.g. before the 1969 German Grand Prix when his teammate and neighbor Gerhard Mitter died, the 42-year-old announced his retirement on TV, after having driven the winning car in a parade through Stuttgart from the factory to the town hall.