Jenson Button lapped Shanghai half a second under last year's Chinese Grand Prix pole position time as he established himself and the Brawn GP team at the top of the times for this year's event.

The Briton and team-mate Rubens Barrichello dominated for most of the second 90-minute session on Friday as teams began experimenting with super-soft tyre - with varying success.

But as has become the norm for Fridays, Nico Rosberg sneaked a fast lap in late-on to split the white and dayglo yellow machines and go second.

The softer rubber, the selection of which has come in for criticism by some drivers, clearly proved to be the faster option. But graining and degradation were major factors, with chunks of rubber bouncing back into drivers' helmets in certain corners.

Until half distance, it was the Red Bulls of Sebastian Vettel and Mark Webber that held sway, having usurped early pace-setters. But that all changed once the Brawns emerged from the pits.

It wasn't championship leader Button that set the pace though, rather Barrichello, whose sequence of laps culminating in a 1:35.881, put him top of the pile.

It looked as if the Brazilian might finally get the better of his team-mate this year, but Button was having none of it. On another set of green-rimmed softs, he went about deposing Barrichello. And after his first lap was aborted when he was held up by Kimi Raikkonen recovering on to the track in front of him, Button posted a 1:35.679.

That ended any debate at the top. That is except for Rosberg, who might have been even higher than second had he not locked up at the end of the straight on another quick lap.

Webber was fourth fastest behind Barrichello. The Australian posted a late flier to push Vettel down to fifth while Toyota's Jarno Trulli was sixth.

Kazuki Nakajima improved to seventh late-on ahead of Timo Glock in the second Toyota. Heikki Kovalainen did a solid job in the slightly less evolved of the two McLaren MP4-24s to go ninth ahead of Sebastien Bourdais who once again cracked the top ten.

Adrian Sutil was 11th fastest despite several spins, half-spins and off-track moments for both him and his Force India team-mate Giancarlo Fisichella.

The grandee teams all had a difficult session, as with the exception of Kovalainen, all of McLaren, Ferrari, BMW and Renault's drivers floundered outside the top ten.

Pos  Driver       Team                       Time              Laps
 1.  Button       Brawn-Mercedes        (B)  1:35.679           35
 2.  Rosberg      Williams-Toyota       (B)  1:35.704 + 0.025   36
 3.  Barrichello  Brawn-Mercedes        (B)  1:35.881 + 0.202   35
 4.  Webber       Red Bull-Renault      (B)  1:36.105 + 0.426   32
 5.  Vettel       Red Bull-Renault      (B)  1:36.167 + 0.488   22
 6.  Trulli       Toyota                (B)  1:36.217 + 0.538   42
 7.  Nakajima     Williams-Toyota       (B)  1:36.377 + 0.698   32
 8.  Glock        Toyota                (B)  1:36.548 + 0.869   40
 9.  Kovalainen   McLaren-Mercedes      (B)  1:36.674 + 0.995   34
10.  Bourdais     Toro Rosso-Ferrari    (B)  1:36.800 + 1.121   34
11.  Sutil        Force India-Mercedes  (B)  1:36.829 + 1.150   30
12.  Massa        Ferrari               (B)  1:36.847 + 1.168   34
13.  Hamilton     McLaren-Mercedes      (B)  1:36.941 + 1.262   28
14.  Raikkonen    Ferrari               (B)  1:37.054 + 1.375   33
15.  Buemi        Toro Rosso-Ferrari    (B)  1:37.219 + 1.540   34
16.  Piquet       Renault               (B)  1:37.273 + 1.594   36
17.  Kubica       BMW-Sauber            (B)  1:37.491 + 1.812   34
18.  Heidfeld     BMW-Sauber            (B)  1:37.544 + 1.865   28
19.  Alonso       Renault               (B)  1:37.638 + 1.959   28
20.  Fisichella   Force India-Mercedes  (B)  1:37.750 + 2.071   31

All Timing Unofficial