We rode it twice (down and then up) this summer.
My recommendation: don’t, it’s really not all that. It’s full of cars and caravans and is slow and boring. The thing it does having going for it is it’s picturesque. We rode it twice by accident as that the road is actually a major bottle-neck for that region. We detoured one day and didn’t realise it was going to take us back up it and around the moauntain (terrain can be deceptive on maps). We got stuck behind 50 Mustangs…
Far nicer roads and passes elsewhere in the Alps and Dolomites. We preferred the Dolomites. See here: Roadtrip 2018 - Switzerland, Italy and a bit of France
We used http://www.bestbikingroads.com to find routes of note and then planned accommodation and overall route by connecting the best roads/passes.