LEAD: Vettel starts pre-season tests; Rosberg leads in old Mercedes

Feb 9, 2012, 16:22 GMT

Jerez, Spain - World champion Sebastian Vettel and two of his main challengers went on a first Formula One pre-season spin on Thursday while Mercedes clocked the fastest time again in last year's model.

Nico Rosberg topped the timesheets on the 4.42km Jerez course in 1 minute 17.613 seconds the day after team-mate Michael Schumacher had dominated.

The two-times reigning champion Vettel drove 96 laps in his new Red Bull with the fastest at 1:19.297. That was third overall as Romain Grosjean had 1:18.419 as the best driver in a 2012 car.

Vettel, who ran away with the 2011 title, will be aiming to emulate Michael Schumacher and Juan Manuel Fangio as only the third driver in the sport to get three titles in a row.

Former champions Lewis Hamilton of McLaren and Fernando Alonso of Ferrari had 1:19.468 and 1:20.412, respectively in their first drives after taking over from team-mates who had driven the first two days.

Rosberg chalked up 118 laps but Mercedes won't have their new car ready until the second round of testing from February 21 onwards in Barcelona.

Three rounds of pre-season testing are scheduled ahead of the March 18 season-opener in Australia.

Not everything went according to plan, though, as Alonso was stopped for a while by a hydraulics problem and Vettel was also in the pits because of a problem.

Force India fared worst, getting no timed lap after spending the rest of the day repairing the car after reserve driver Jules Bianchi crashed early on.