BuddyPress.org

Thx *danbp*
With define( ‘BP_GROUPS_DEFAULT_EXTENSION’, ‘members’ ); the default tab for all groups (private and public) DOES change.
But if the user is not a member of a private group, he cannot see the group’s page to request a membership. However, if the user is already a member of private group, of course everything is OK and the default tab is changed as the same as the public groups.
If I don’t remove ‘home’ tab in the group pages, then everything is fine though!