Tough climb of 18.8Km long and a little over 1000 altimeters. It has some steep parts but we never had to push our bike, we could keep cycling all the way up coming from Phroa.
There's very little to no possibility to get food on the way so make sure you pack enough snacks and you're good to go!
Don't underestimate the downhill, there's alse quite some climbing involved still.
Doable for fully loaded bicycles :) and beautiful views!