GB duo ease through qualifying
Great Britain's Jess Varnish and Victoria Pendleton set a team sprint world record in qualifying only to see China go better at London 2012.
The eight fastest teams advanced to the first round, with Varnish and Pendleton clocking 32.526 seconds to better the time Germany set in winning Track Cycling World Championships gold in Melbourne in April.
But China's Gong Jinjie and Guo Shuang went faster still in the fifth and final heat, clocking 32.447secs.
German duo Kristina Vogel and Miriam Welte were third fastest in 32.630, with Australia's Anna Meares and Kaarle McCulloch fourth quickest in 32.825.
The four fastest teams from the first round were set to go through to the medal rounds in an event which was wide open.