What's a great Australian off-road cycling destination?

Answer 1

There are fire trails in just about all national parks. If you don't mind some up and down the Blue Mountains outside Sydney, and the Snowy Mountains south of Canberra are rewarding.

A lot of rail trails are opening along former rail lines - don't know whether this meets your definition of off-road.

Answer 2

Ayers Rock, in the Northern Territory you might need somebody to accompany you in a van,its a bit far from anywhere! nearly in the middle of Australia.I think the land mass is about the same as the USA.