Jenson Button has set the fastest time in Friday's practice sessions for the Chinese Grand Prix.
The Brawn GP driver lapped Shanghai half a second under last year's Chinese Grand Prix pole position time after he and team-mate Rubens Barrichello dominated for much of practice.
Only in the final minutes did Williams driver Nico Rosberg set a quick time, to go second fastest and demote Barrichello to third.
The big talking point of the weekend is Bridgestone's super-soft tyre, which many teams fear is not durable enough to be effective on the super-grippy track surface for long.
Drivers used the test session to sample the rubber and, while it was clearly the fastest tyre, it degraded quickly and chunks of rubber could be seen bouncing back into drivers' helmets in some corners.
1 Button (Brawn-Mercedes) 1:35.6792 Rosberg (Williams-Toyota) +0.025s3 Barrichello (Brawn-Mercedes) +0.202s4 Webber (Red Bull-Renault) +0.426s5 Vettel (Red Bull-Renault) +0.488s6 Trulli (Toyota) +0.538s7 Nakajima (Williams-Toyota) +0.698s8 Glock (Toyota) +0.869s9 Kovalainen (McLaren-Mercedes) +0.995s10 Bourdais (Toro Rosso-Ferrari) +1.121s11 Sutil (Force India-Mercedes) +1.150s12 Massa (Ferrari) +1.168s13 Hamilton (McLaren-Mercedes) +1.262s14 Raikkonen (Ferrari) +1.375s15 Buemi (Toro Rosso-Ferrari) +1.540s16 Piquet (Renault) +1.594s17 Kubica (BMW-Sauber) +1.812s18 Heidfeld (BMW-Sauber) +1.865s19 Alonso (Renault) +1.959s20 Fisichella (Force India-Mercedes) +2.071s