permissions question: no writing by users even when users in group with rwx on object

[Kholdstate]

I created a shared drive for two users on a f11 system. I installed the physical drive, formatted it with ext4 and mounted it under /media/stuff.

I created the group "trusted" and changed permission on stuff with "chown root:trusted" and added both users to the group trusted (stuff has permission rwxrwxr-x). However this wouldn't allow any of the users in trusted to write to the directory. It does however work if I set the owner to any of the two users (both users can create files in the directory when I do this).

Is this in fact how permissions work or did I set something up wrong? Does a root owned directory or file with a different group than root that has write access still not give members of the group write access?