Central North island has excellent mountain biking tracks: Craters of the Moon in Taupo, 42nd Traverse, Fishers Track, Old Coach Road, Mangapurua Valley just to name a few. Check with locals about the conditions of the tracks, in the winter some tracks are unrideable and with the pumice in the soil, you will ruin your brakes! Check weather and be prepared, a lot of these places have limited cell phone coverage and can be in very rural areas so you need to be self sufficient. Definitely bring a head light; it has often come to good use.

When driving to the Central North, the route through the King Country (Te Awamutu, Te Kuiti, and Taumaranui) is a nice alternative to SH1. Nice scenery.