Expand existing site topics or create a new one

Hey!

I have a quick question regarding the topics of a site.

I got a content website that is focused on a quite specific topic. The name of the site is chosen based on it as well. However, I want to start covering new a topic that is somewhat related to the existing one. Would it be a bad idea to simply expand the content topics of my current site, or should I create a new site?

Cheers!