How to divide my community into 2 parts?

[Kosiak]

I have an general thematic forum and over time I want to bring parts of it (user base, and messages from certain sections) to another forum.

For example:
Sections “Cars” and “Trucks” forum about-all.com I want to put on the forum about-cars.com

Can I do this?
What is the separation procedure?

[PitaJ]

The closest thing I can think of is essentially cloning your forum (copying the database around) and then disabling certain categories on the specific forums.