Fisher started competing in road and track races at the age of twelve. He was suspended from the sport in 1968 on the grounds that his hair was too long. However, by 1972 this rule had been repealed and Fisher resumed his racing career.
Inspired by a bicycle he saw built by Russ Mahon, Fisher developed the Schwinn Excelsior X bicycle in 1975. Innovations in the model included drum brakes, thumb shifters, motorcycle brake levers and cables, and a triple chain ring.
The next year, he and Charlie Kelly started the "Repack" race, so named because the tortuous route chosen near Fairfax, California made it necessary for riders to repack their hubs with grease after almost every run.
Fisher coined the term "mountain bike" in 1979, after a phrase he had heard used by a mechanic. The same year, he and Kelly founded MountainBikes, the first company to specialize in the manufacture of this type of bicycle. Frames for the bikes were built by Tom Ritchey. The first model sold for $US 1300; 160 were manufactured in the first run.
1980 saw the introduction of Shimano components into MountainBikes's products, and also an attempt to trademark the term "Mountain Bike." The company dissolved in 1983; Fisher founded Fisher MountainBikes the same year. This company was purchased by Trek Bikes in 1993.
Fisher was inducted into the mountain bike hall of fame in 1988. Outdoors magazine named him one of the "50 who left their mark" in the sport, and Smithsonian magazine honored him in 1994 as the "Founding Father of Mountain Bikes."