Northwest of Christchurch near Cass in the Arthurs Pass National Park, the Poulter Valley Track is tenatively open to mountain biking through December 2010. The route has amazing scenery and has two huts along the way for overnight stays. The distance from the start of the track to the Poulter Hut is about 27km (mountain bikes are not permitted past Poulter Hut). The first 18km are difficult due to ruts and numerous river crossings. The best riding is the last 9km.
To reach the trailhead from Arthur Pass village, head east on SH73 for 25km to Mt White Road. Turn onto Mt White Road. After 1km, the road crosses Waimakariri River. Then the road heads true left through the Poulter River (actually down the river), passing the park boundary fence and up to Mt White Station after about 25km of unsealed road.
Note: there are numerous hikers, so make sure to slow down and be considerate.