Rallarvegen - Mydral to Flam

Yes you can take the train up the hill to Myrdal and ride back down again. However you need to get off at some stop before Myrdal itself, because the track doesn't go all the way up to Myrdal station, I'm sure you can get local advice as exactly where to get off. I have taken a bicycle down the hill from Myrdal station to the track, and it wasn't much fun, a steep path with very short zigzags, and then a tricky narrow gate to get through. Though you do get to see some waterfalls on that bit.

If you do feel like cycling up the hill, it isn't very steep, it is quite a gentle climb. The track is well surfaced too, or at least it was when I did it. Norwegian untarmacked roads are mostly very good.

It took us about 40 mins to cycle down the hill, I forget whether that includes the path. Cycling up, well that can be very variable depending upon the individuals.

Myrdal to Flam is a very short ride. Last year I did the ride from Finse to Flam. The section up in the tundra is amazing and worth taking the time to ride. It took us about 4 hours, which included a lot of stopping to take photos and have lunch. If you're regular cyclists, I think it's a must-do, though it will take most of a day given the train ride and a stop for a picnic.

With 4 days in Flåm I would definitely take the train up to Finse, Hire the bike you can also book a bike at Finse and ride to Flåm. Finse is at 1222meters the track winds gradually up to 1350meters, or there abouts and then gradually down to Mydal at 800meters. There’s a steep section down to 500meters but it’s not dangerous. Then it’s an easy ride down to Flåm. The hole trip is 60km. The best part is Finse to Mydal. Sometimes you see reindeer. Forget riding from Flåm to Mydal. You can also take the train past Finse to Haugastol at 1000meters which from memory adds another 22km.