Travel down the coast to Hokitika, where you'll find the area known as Blue Spur. During the New Zealand gold rush Blue Spur was home to around 2,500 people, today it is a hub for mountain bikers.
Built by local bikers for pure fun, the Blue Spur track is actually a network of tracks all within easy riding distance of Hokitika. With names like The Edge, Stags Drop, Bad Boys and Seesaw, the tracks each have a character all of their own. Spend the day trying out as many as you can. Be sure to finish with the Tunnels Track, which leads through an old mining tunnel.
If you have time, stay an extra day and explore the West Coast Wilderness Trail from Kumara to Cowboy Paradise.