By Alan Baldwin
SPIELBERG, Austria (Reuters) - World champions Mercedes dominated Austrian Grand Prix practice on Friday, Formula One leader Nico Rosberg setting a record pace around the scenic Red Bull Ring with the fastest lap in both sessions.
The German set a best time of one minute 07.373 seconds, 0.357 quicker than team mate and triple world champion Lewis Hamilton on a bright but cloudy morning and he was again top in the afternoon with a 1:07.967.
The second session was punctuated by heavy rain that sent waves of water rippling down the pit straight before the sun returned.
Hamilton, 24 points behind Rosberg after eight of 21 races, was second in both.
Ferrari's Sebastian Vettel, who is set for a five-place grid penalty in Sunday's race for an unscheduled gearbox change, was third and fourth respectively after spinning off in the afternoon.
Fellow German Nico Hulkenberg was third in the second session for Mercedes-powered Force India.
Since Austria returned to the calendar in 2014, after an 11-year absence, Rosberg has won both races and Mercedes-engined cars have swept the podium.
Red Bull's Daniel Ricciardo, celebrating his 27th birthday, was fifth fastest in each of the two practice sessions.
Rosberg's fastest lap on Friday, using the quickest ultrasoft tires on a resurfaced track, compared to the 2015 pole position of 1:08.455 and the race lap record of 1:08.337 set by compatriot Michael Schumacher for Ferrari in 2003.
It was also three seconds quicker than his own fastest lap of 1:10.401 in first practice last year and easily the fastest lap yet of the circuit.
While Rosberg had a clean first session, Hamilton spun into the gravel and triggered the virtual safety car at turn eight. Frenchman Romain Grosjean, in the Haas, also spun off as he avoided the Mercedes.
The circuit's revised kerbs also caused problems for Red Bull's Max Verstappen, who called them 'unbelievable' and 'dangerous' after two incidents.
The Dutch 18-year-old ended up in the gravel half an hour before the end of the session with a damaged suspension after earlier smashing his car's front wing on the kerb at the penultimate corner.
"The yellow kerbs in the fast corners are really dangerous," he said over the car radio.
The new kerbs have been introduced to force drivers to respect the track limits.
(Editing by Ed Osmond)