Rallarvegen Cycle Route
The Rallarvegen Cycle Route is a well-known cycle route in Norway. It starts at Finse, 1222 meters above sea level, and ends in Flåm.
Take the Flåm Railway to get to Finse. The trip from Finse to Flåm is 53 km in total length, so you may want to shorten it by starting at another point such as Hallingskeid (32 km) or Vatnahalsen (17 km).
Regardless of which version you choose, you will experience wild nature with waterfalls and steep slopes. There are several companies offering bike rental in Flåm.
For more information, see this site.