break with convention

To do something in a new, different, or unique way; to defy or go against conventions. I'm from a family of doctors, so I really broke with convention when I went to art school! My best friend just got engaged, and she wants to break from convention and elope. The artist always tried breaking with convention in everything she made, ignoring all the accepted norms of her contemporaries.

buck convention

To act or develop in an unexpected, surprising, or unforeseen way that runs contrary to normal conventions or expectations. The artist always tried bucking convention in everything she made, ignoring all the accepted norms of her contemporaries. The politician made an entire career out of bucking convention, seemingly always at odds with the norms of the political world. Although property values in our city are down overall, one neighborhood is bucking convention and still getting fair market value.

fly in the face of (something)

To be or act in clear conflict with or opposition to something else. I can't believe you said something so awful. It flies in the face of everything we stand for! They want to change the entire direction of the project, completely flying in the face of all the hard work we've done so far. Her controversial new theory flies in the face of everything we know about quantum mechanics.