Photo from @surselvatourism
Steepest kilometer starts at km 9.5 (11.2%)
Strava Members state:
Michiel Van Lonkhuyzen Hello, Alp da Riein is fully paved except for the last 200m. The pavement above Siat ends at about 1550m altitude. Above there is not really suited for a road bike. See also, http://www.cyclingcols.com/col/Siat and http://www.cyclingcols.com/col/Riein
Philipp K Hi, yes you can go up till Alp da Riein with a Road Bike. The road is paved, and after Riein cars are not allowed. Very beautiful, very quiet: Just you and the cows... :-) Reaching Alp da Riein you turn and go back/down the same way... Enjoy it!
Laurent Outang Hi John, the road is paved from Ilanz to Alp da Rien (1855m) so it shouldn't be any problem with a road bike!