Well, it's a question of aesthetics. Generally, you want your wheel well gap to be shorter than your sidewall height, or at worst, equal. A 215/45 will make your gap look huge, and the car will look lifted.
Function before fashion.
'96 Contour SE
"Toss the Contour into a corner, and it's as easy to catch as a softball thrown by a preschooler." -Edmunds, 1998