54,4 km (with 1800 m elevation gain)
To call the bike course of the Challenge Davos “special” would be quite an understatement. You start swimming in the Davossee at an altitude of about 1500 meters above sealevel. But don´t expect to go downhill from there – to the contrary. Well, the first part is flat – for about 1,5 km. Then you go directly up the Flüelapass (2.383 m), go down on the other side, turn around and go back up again and then downhill back to Davos. So the 54,4 km bike course contains no less than whopping 1.800 meters of elevation gain. You certainly won´t need a TT-bike here.
Despite the rather short bike leg it´s still classified as “middle distance” – from the organizer as well as here on this site. Although we usually define a middle distance by a overall distance of at least 60 km. But you will probably still spend more time on the bike than in most other middle distance races ;-).