American Kristin Armstrong defends her Olympic time trial crown with a storming ride.
Britain's Emma Pooley, a silver medallist in Beijing in 2008, finished sixth and Lizzie Armitstead, who won silver in Sunday's road race, 10th.
Germany's reigning world champion Judith Arndt claimed silver, while Russian Olga Zabelinskaya matched her bronze in the road race.
BBC Sport's Oliver Regan reports.
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