So although Rosberg set the fastest time of the session he did it 20 minutes later than the McLarens, in which time the track will have become faster by several tenths of a second. Remember also that we saw Lewis Hamilton abort a lap on which he was set to improve after catching a Lotus in the final sector.
Interestingly, we know from the radio broadcasts that on Rosberg’s two laps when he set his best time he only activated his F-duct for the second. As the graph above shows that second lap was 2.3 seconds faster. However Rosberg was 7.5kph slower than Hamilton through the speed trap.
As usual the McLarens showed great straight-line speed. Jenson Button was fastest, cutting the beam at 315.2kph and Lewis Hamilton managed 314kph. But the next fastest driver, Sebastien Buemi, was 2.5kph slower.
There seems to have been no major leap forward from the Red Bulls as they test the new version of their F-duct. Sebastian Vettel hit 306.7kph which was 15th fastest, though more or less on a par with Robert Kubica’s similarly-engined car.