Pietro Ghersi won a 1924 cc Moto Guzzi the Circuito del Lario - race on Lake Como. In 1925 he was on the Norton IV Grand Prix of Nations at the Circuito di Milano behind Mario Revelli di Beaumont Vice-European Champion in the 500 cc class. In the same year he won A.J.S. the Italian road championship in the 350cc category. 1928 won the Italian Grand Prix on Norton Germany at the Nürburgring in the 350cc class.
Together with his brother Mario and Luigi Arcangeli began Pietro Ghersi 1926, 1929 and 1930 on Moto Guzzi in the Tourist Trophy on the Isle of Man, which was considered the toughest bike race in the world. In 1926, he turned in 250 cc race ( Lightweight TT ) the fastest lap of the race and took second place behind the Irish CW Johnston. After the race, but was disqualified because of the use of an undeclared spark plug type. 1929 led the Italians to the 250cc race, but had to retire due to an engine failure early. In 1930, he crashed in training on Goosenack and could not compete in the race.
As early as 1927 Pietro Ghersi went to both automotive and motorcycle racing. In 1929 he took on OM fifth place in the Mille Miglia. In 1930, Ghersi won together with Attilio Marinoni on Alfa Romeo 6C 1750 GS, the 24 - hour race at Spa -Francorchamps and was together with Franco Cortese fourth at the Mille Miglia. In March 1933, the Italians founded in Genoa in his own racing team, which had a 2.3 -liter Bugatti Type 35, a 1.1 -liter Maserati - seater and a 2.3 -liter Alfa Romeo. 1934 started Ghersi for the Scuderia Ferrari in 1935 and again in 1936 on a private Maserati 8CM. After 1937, he played a few races, Ghersi occurred in 1938 and 1939 for the Scuderia Torino on Alfa Romeo Grand Prix cars and Maserati Voiturettes at numerous racing events. Then he ended his active career.