Scheidegger began racing in the 500 cc solo class, eventually becoming Swiss champion before switching his attention to sidecar competition. He formed an early partnership with German passenger Horst Burkhardt, and together they entered the world championship for the first time in 1957 at Monza, finishing a notable fourth at the final Grand Prix of the season.
The 1958 campaign offered limited results on an underpowered BMW, but 1959 brought a more competitive showing. Scheidegger and Burkhardt opened the season with a win in France at Clermont-Ferrand, followed by a third at the Isle of Man TT on the Clypse Course, fifth in Germany, and third in Belgium, which together lifted them to third overall in the championship.
Steady progress through the early 1960s established the partnership as consistent front-runners. The 1960 season brought second place overall despite no wins, built on a series of podium finishes. In 1961 the team scored two victories, in France and Belgium, and added three runner-up finishes, yet again finished second in the championship.
From 1962 onwards Scheidegger paired primarily with British passenger John Robinson after Burkhardt departed to compete in solo classes. The Robinson partnership proved highly competitive. In 1963 the duo placed third in the championship with a win and multiple podiums. The 1964 season opened with a win in France and closed with a win in Germany, earning second place overall.
The 1965 campaign was a dominant display. Scheidegger and Robinson won four races and took three second places across the season, claiming the Sidecar World Championship at the final round at Monza. If 1965 represented a statement of dominance, 1966 was arguably even more complete: the pair won every race they entered across the season.
However, 1966 was also a year of controversy. At the Isle of Man TT, Scheidegger and Robinson were excluded from the results following a fuel irregularity ruling. The FIM Sidecar World Championship title was awarded to Max Deubel and Emil Hörner as a consequence. Scheidegger and Robinson appealed the decision, and three months later they were reinstated, recovering the championship.
On 26 March 1967, Scheidegger was killed while leading a race at Mallory Park in England. His BMW sidecar outfit crashed at high speed at Shaw's Corner after a bracket that held both the rear brake torque arm and the gear change cross shaft failed. The subsequent inquest revealed that the bracket had not been properly brazed and that cracks in its brazing had been present for a considerable time, constituting a pre-existing mechanical defect.
Passenger John Robinson suffered a broken leg in the crash and subsequently retired from sidecar racing entirely.
Fritz Scheidegger's career arc — from solo champion to two-time sidecar world champion in the sport's most contested era — established him as one of the defining figures of 1960s Grand Prix sidecar racing. His partnership with John Robinson produced back-to-back championship seasons at the highest level of competition. His death at Mallory Park at the age of 36 cut short a career that appeared far from its conclusion, and the circumstances surrounding his 1966 championship remain among the more complex episodes in the sport's historical record.