NUERBURGRING, Germany (Reuters) - Lewis Hamilton and Sebastian Vettel set the pace in practice for the German Grand Prix on Friday with no sign of the tyre blowouts which marred last weekend's British race at Silverstone.
Hamilton, who won at the Nuerburgring two years ago with McLaren, topped the timesheets for Mercedes in the first session ahead of German team mate Nico Rosberg while Red Bull's championship leader Vettel was only eighth fastest.
However, the German triple world champion, who has never won a Formula One race on home asphalt or in July, sped around the track with the day's top time of one minute 30.416 in the afternoon session.
"Mercedes were very quick this morning. I wasn't entirely happy with the car this morning. I was quite happy with what we had this afternoon," Vettel told reporters.
Rosberg was second fastest again with a 1:30.651 as Mercedes were roared on by small pockets of home fans sprinkled among the half empty stands at the rural western German venue. Hamilton, the 2008 champion, was only eighth fastest.
Red Bull's Mark Webber, preparing for his final German Grand Prix as he quits for endurance racing at the end of the season, was third quickest in both practice runs at the circuit where he took his first Formula One victory in 2009.
The Grand Prix Drivers' Association announced on Thursday that they will withdraw from Sunday's race if the multiple tyre blow-outs seen at Silverstone occur again but both practice sessions were free of incident.
After the intervention of the governing FIA, Pirelli has brought upgraded rear tyres to the Nuerburgring with an inner belt made of the synthetic fibre Kevlar rather than steel.
The cooler tyres were expected to aid Mercedes and Red Bull, based on this season's analysis, and practice bore that out.
"It was an interesting day for us as we had to adapt to the new tyres. They are different and require a different set-up, so today was a good opportunity to learn something. We want to understand them quicker and better than the other teams," Rosberg said in a team release.
"Generally it seems that we are quick again over one lap and the long run was not bad."
The tyres are not totally new to the teams as Pirelli offered them for practice in Canada last month but bad weather meant teams used them sparingly and did not gather much data.
Practice in Germany also began under gloomy skies, which mirrored the mood of Spaniard Fernando Alonso after he ground to a halt just off the track in his first practice lap.
Ferrari said on Twitter that it was an electrical problem and the championship contender only managed one more lap before being recalled to the pits for further checks.
Alonso, 21 points behind Vettel after eight of 19 races, was able to take to the track normally second time around and was sixth quickest as he targets a first front row on the grid since the German Grand Prix at alternate host Hockenheim last year.
Hamilton edged out Sunday's Silverstone winner Rosberg in early practice with a time of 1:31.754 compared to 1:31.973 but the Briton's engineer reported problems with the rear wing DRS system over the radio.
Third practice takes place before qualifying on Saturday with weather forecasts looking brighter.
Marussia's Venezuelan reserve driver Rodolfo Gonzalez was allowed to take Jules Bianchi's car for first practice and clocked 1:37.459 as the slowest out on track. Bianchi was back in the afternoon and was second slowest.
(Editing by Alan Baldwin)