Generalzing PR & SERP Strength To Other Niche

Or will new content/keywords be sandboxed?

[janejanejane]

I maintain a website with decent PR that has done very well in the SERPs for our niche. We're considering adding an trangentially-related product line that is in a very competetitve (keyword) sphere. Any thoughts or exerpience on this?

Is it possible to leverage your PR/SERPS strength from your original niche to a new content, keyword area?

Or will your new pages in this different niche become sandboxed?

Or by adding tangentially-related new content can you subvert your original high rankings by going for another competitive niche?

Thanks for any thoughts on this.