For skilled riders, the Bowenvale Downhill Track is the best ride down from the central part of Summit Road to Christchurch city below. It goes down a steep sided valley with enough technicality to keep it interesting - including the odd drop, steep switchbacks, some rocks to navigate around, tricky variations, some surprises, some ruts, some grade reversal, some exposure, lots of fun and nice views all the way.
You come out right at the bottom of the Port Hills on Bowenvale Avenue. It's then a short ride to Centaurus Road.
A great loop from the city is to ride up the Rapaki Track, along the Mount Vernon Track and down the Huntsbury to the Bowenvale Downhill. If you parked your car at the bottom of the Rapaki Track, ride on down Bowenvale Avenue and back along Centaurus Road.