Both drivers started testing different set-up packages before midday as there are some interesting new directions with this car and the Bridgestone Potenza tyres.
Other notable elements of the design included another step in the undercut of the sidepod leading edge, with top louvres for cooling.
The other prominent differences from the FW28 included large chimneys expressly for cooling at the season's first three races in Australia; Malaysia and Bahrain, and a narrower engine cover spine.
The FW29 proved a consistent challenger for points, but was well off the pace of the front running McLaren and Ferrari cars, and the new BMW Sauber team formed by Williams's old engine partners.
However, Rosberg proved to be a faster driver, scoring frequent points finishes and consistently outpacing Wurz, particularly in the 2nd half of the season.