There are some very steep grades and tight turns going the Payson route. We drive the Salt River route with our 5er several times a year. It really isn't bad. I'm quite comfortable with it. The only time it makes me a little apprehensive is on a Sunday afternoon of a holiday weekend. The traffic can get intense.
I've seen many commercial big rigs on that route. Just make sure you stay in the right lane when you get to a passing lane to let traffic clear. Also if it backs up behind you, pull over into a turn out to let it clear. You'll be fine.
Jim - Tucson
2016 Ford F350 Turbo Diesel SRW 4x4
2017 Grand Design Reflection 297RSTS
2013 Ford F350 Turbo Diesel SRW 4x4 (Destroyed by fire - 8/29/16)
2014 Grand Design Reflection 337RLS (Destroyed by fire - 8/29/16)