Hey!
Go to www.groundeffect.co.nz & pick up a copy of the Kennett Brothers guide to Mtn biking in NZ.
The Queen Charlotte Track at the top of the south island is supposed to be a beaut!!!
If you're at the top of the south island, take the ferry from Picton to Wellington & try some of the tracks there!
Are you flying to the south island or driving down from the north??? If you can find a group, I recommend the 42nd Traverese ONLY if you have a group. Don't try it with only two of you.
C