I love the classic look with a wider tire in the back.......what is the widest tire that will fit without looking stupid, on the standard 19x9 wheel on the Ecoboost HPP?

 

The largest recommended tire for a 19 x 9" wheel is a 275.

 

Will it look goofy from a sidewall perspective.....if not maybe when I get the all seasons, get the 255/40/19 on the front and 275/40/19 on the back......

 

275 is pushing it for a 9" wheel but I think it is in the recommended range

you can look up all of the specifics on Tire Rack -- pick a tire and size and then look at the "sizes" and "specs" tabs for more details, such as the overall tire diameter and the recommended rim width

it's hard to say how much difference in sidewall height will be noticeable, and some folks like to see a bit more rubber on the back when looking from the side as well as the rear . . . I'm guessing 1/4-1/2" taller tire on the back is probably not very noticeable, beyond that it might be noticeable