Lewis Hamilton won an all-McLaren battle for early pace ahead of the Australian Grand Prix, pipping world champion team mate Jenson Button for the fastest lap at a rain-affected second practice session on Friday.
After rain forced drivers back to the pits to change tyres a few minutes into the session, Briton Hamilton emerged during a break between showers to overtake Button for the fastest lap at Albert Park with a time of one minute 25.801.
Button, slower by under three tenths of a second, attempted to wrest back the pace from his compatriot, but their times stood for the remainder of the session as teams grappled with tyre selection amid intermittent showers.
"I didn't go out when it was wet," Hamilton told reporters.
"(We) still have to make a couple of changes going into P3 (third free practice session) but good running, good feeling off both sets of cars."
With rain easing to allow the track to dry late in the session, Michael Schumacher pushed his Mercedes to the third fastest lap but was deposed shortly after by Australian Red Bull driver Mark Webber.
With traffic causing problems at times on the tight street circuit, the McLaren drivers came close to grief when overtaking BMW Sauber's Pedro de La Rosa late in the session.
Webber's team mate Sebastian Vettel lost control towards the finish, ending up on the gravel in a possible preview of things to come, with rain forecast for part of the weekend.
The German finished 16th, behind Ferrari's Fernando Alonso and in front of the Spaniard's Brazilian team mate Felipe Massa.
Renault's Vitaly Petrov, Russia's first F1 driver, posted the fifth fastest lap in the session, while Polish team mate Robert Kubica had the 11th fastest after setting the pace in the earlier session.
Hispania's (HRT) Indian driver Karun Chandhok, whose debut for the new team was in qualifying at Bahrain, was again denied a practice time when his car ground to a halt soon after leaving the pit.
Britain's Paul di Resta marked his track debut at a grand prix weekend with the 11th fastest lap in the first session, after he replaced Force India''s German race regular Adrian Sutil.
BMW Sauber driver Kamui Kobayashi lost part of his wing when he skidded off track, then had it come clean off minutes later for a second red flag in an eventful first session.
