Lewis Hamilton topped the timesheets in opening free practice for the 2012 Chinese Grand Prix, but fickle weather conditions meant that his one-second advantage was largely meaningless in the context of the entire weekend.
The Briton completed only half the number of laps of most of his rivals, as an initially dry session suffered the effects of overnight rain and then the return of the precipitation, but produced a late 1min 37.106secs lap on slick tyres to open out a huge gap over the field. Mercedes' Nico Rosberg had crossed the line just seconds ahead of the McLaren to move into P1, but Hamilton rewrote the target time with little time for anyone to respond.
A damp circuit meant that there was precious little action early on but, as it dried and slicks were a viable option, drivers progressed from mere installation laps and Mark Webber was the first to set a meaningful benchmark. The Australian eventually returned to the pits having posted a 1min 39.558secs effort, and would remain at the head of the field for almost an hour as the return of the rain either kept drivers indoors or prompted slower laps on Pirelli's intermediates as they attempted to get a handle on the conditions lest they return on raceday.
Only in the final quarter of the 90-minute session did the surface briefly begin to dry again, allowing the teams to consider a return to slick-rubber running. Michael Schumacher quickly replaced Webber at the head of the times, before the Australian hit back, going half a second faster than he had previously. Hamilton then took his first turn at the top, before Rosberg thought he had done enough on his final flying lap. The McLaren was just behind the German, however, and left the field open-mouthed as he trimmed a full second from the target.....
Rosberg and Schumacher filled second and third for Mercedes, which goes into the weekend knowing that there protests over its rear wing should have been silenced, while Webber was pushed back to sixth in the closing stages as Sauber's Sergio Perez and Kamui Kobayashi both found enough time to better the Red Bull. The Australian ended the session just ahead of team-mate Sebastian Vettel, who complained that his DRS had stopped functioning, with Jenson Button next up after being denied a late flier by traffic on the long back straight. Toro Rosso duo Daniel Ricciardo and Jean-Eric Vergne rounded out the top ten.
Less happy were Ferrari's Fernando Alonso and Felipe Massa, who returned to form with spots rounding out the top half of the table, and Kimi Raikkonen, who also suffered DRS problems and was restricted to 24th spot with a time some 13 seconds off the pace. Lotus team-mate Romain Grosjean had led the initial pursuit of Webber, but sat out the fastest part of the session, and dropped to 17th, leaving him in amongst the Caterhams and Marussias.
Reserve drivers Valtteri Bottas, Giedo van der Garde and Jules Bianchi all took part in the session, for Williams, Caterham and Force India respectively, with the Frenchman running for the first time since binning his VJM05 in the opening minutes of pre-season testing in Spain. They finished 13th, 19th and 20th after mustering just 27 laps between them.