I'm working on a redesign of an app with a tab bar for navigation. Currently, the main screen is the middle tab in the tab bar. The application is a few years old and already has a solid user base.
Many large applications that use the tab bar, keep the main screen as the first tab bar item. Think screens like "Home" (like the screenshots), or "News Feed" (like Facebook). Always on the far left.
My question is, is this design pattern so common that it is justified to switch the tab bar layout around? My users are familiar with the middle tab being the main screen of the app. Best practises seem to suggest the main screen should be the first tab in the tab bar.
Is there any research that shows that the tab bar item order helps improve usability and/or conversion? Or is it better to leave things as is, because my user's are used to that?