After being stunned by Nico Rosberg\'s qualifying and race pace in China, McLaren re-asserted itself in opening free practice for the Bahrain Grand Prix as Lewis Hamilton posted the fastest time of the morning. No doubt relieved to finally be able to pull on their helmets and put the questions about politics to one side, the drivers still made a tentative start to the 90-minute session, and Hamilton was slower than most to go chasing a time, When he did, however, he was immediately on the pace, with his initial flying effort netting second spot and a follow-up two laps later pushing him to the top of the pile. With all teams concerned about rear tyre wear, there was a balance to be struck between gathering data and preserving rubber, and Hamilton completed fewer laps than most in posting his 1min 33.572secs benchmark. The Briton racked up just eleven tours of the Bahrain International Circuit, while others - notably both Force Indias and Pastor Maldonado\'s Williams - were into the high twenties, but also ended his session early after mechanics spotted a problem at the rear of his MP4-27 during a simulated pit-stop. According to paddock rumour, Paul di Resta and Nico Hulkenberg may have been banging in the miles as part of a plea for Force India to be excused participation in second practice later in the day, the team having been spooked by some of its members getting caught up in a firebomb incident on their way home from the circuit on Thursday. With post-practice debriefs and set-up work usually taking personnel into the night, the Silverstone-based squad is naturally conscious of the risk of a possible repeat. Talks are apparently underway with Bernie Ecclestone regarding a pass on FP2. Both di Resta and Hulkenberg were notable for using the softer Pirelli tyre during their 26-lap efforts, something not usually looked at until second practice, and both benefited as they annexed third and sixth spots respectively. That put the Scot behind Sebastian Vettel, as well as Hamilton, as the world champion posted an improved second spot mark of 1min 33.877sec to end the session a matter of tenths shy of Hamilton\'s pace. Red bull team-mate Mark Webber, who has out-qualified Vettel in each of the three rounds so far, was eighth fastest, just under a second off Hamilton and the last driver to get within a second of the McLaren. Ahead of the Australian were both Mercedes, with Shanghai race winner Rosberg fourth fastest, narrowly ahead of the man who followed him home in China, Jenson Button, and Michael Schumacher seventh, fractionally quicker than Webber. There is little to be learned from FP1, however, and much could change in the second session. For the record, Lotus duo Kimi Raikkonen and Romain Grosjean rounded out the top ten, with Sauber, Williams and Ferrari mixing it immediately behind them. Among the surprises of the session, meanwhile, was an apparent lack of pace at Toro Rosso, which had Jean-Eric Vergne down in 17th, just over a tenth ahead of Caterham\'s Heikki Kovalainen, and Daniel Ricciardo three spots worse off, behind the second green machine of Vitaly Petrov. Charles Pic also got the better of Marussia team-mate Timo Glock, who endured the only major spin of the session.