Bahrain FP2: Rosberg retains the upper hand

Championship leader Nico Rosberg lapped more than a second quicker than last year's pole position time as Mercedes dominated Bahrain Grand Prix practice on Friday.

The German, who is chasing his fifth victory in a row after winning Formula One's season-opener in Australia and the last three races of 2015, led both sessions with his triple champion team mate Lewis Hamilton second.

Rosberg's best lap of one minute 31.001 seconds, in the floodlit evening session at the Sakhir circuit compared to Hamilton's 2015 pole of 1.32.671.

Hamilton, winner for the past two years in Bahrain, was the only other driver to lap below the 1:32 mark with a best effort of 1:31.242. McLaren's Jenson Button produced a third best time of 1:32.281 on the super-soft tyres.

Ferrari's Kimi Raikkonen had been third fastest in the afternoon practice, a hefty 1.834 off Rosberg's pace on the same soft tyres as the Mercedes pair.

The Red Bulls of Australian Daniel Ricciardo and Russian Daniil Kvyat were fourth and fifth in that same session but Toro Rosso's Max Verstappen and Raikkonen filled those places in the evening.

Ferrari's Sebastian Vettel, third in Australia, was sixth but pulled off the track and stopped late in the second session with a loose wheel.

"The rear-left corner (wheel) is not tight. The nut is not on, that was the problem," the four-times world champion said over the team radio.

Belgian Stoffel Vandoorne got to grips with the McLaren ahead of his Formula One race debut as stand-in for the injured Fernando Alonso and was 18th on the 22-driver timesheet in the first session.

The rookie moved up to 11th after another 30 laps in the second practice after flying from Japana day earlier where he is racing in the Super Formula series this season. He had not previously driven the 2016 McLaren.

Spaniard Alonso was ruled out on Thursday, after failing to pass a medical following his big crash in Australia.