Fritz Riess' motorsport career began between 1936 and 1939 with motorcycle off-road and reliability rides on BMW. After the Second World War , he first drove Veritas and AFM racing cars. On August 3, 1952, at the German Grand Prix , he took part in the race with a Veritas RS and came in 7th, two laps behind the winner, Alberto Ascari ( Ferrari ). It was his only participation in a run for the drivers' world championship.
He achieved his greatest success in motorsport in the sports car. In 1952, he and Hermann Lang achieved overall victory at the 20th edition of the 24 Hours of Le Mans . It was Daimler-Benz AG's first appearance in this race after the Second World War. Lang and Riess won in their Mercedes-Benz 300 SL with an average speed of 155.575 km / h and distanced their two team colleagues Theo Helfrich and Helmut Niedermayr by one lap.
In the same year Riess won the sports car class up to 2000 cc on Veritas at the Eifel race , 1.3 seconds ahead of Toni Ulmen , also on Veritas.
In 1953 he drove a few sports car races in Alfa Romeo before giving up racing for family and professional reasons.