March 1 (Reuters) - Lotus put their recent problems behind them with French driver Romain Grosjean setting the pace on the first day of Formula One's final pre-season test in Barcelona on Thursday.
The former Renault team, who have 2007 champion Kimi Raikkonen making a comeback as their main driver, had to quit the second test last week due to a chassis problem.
The Malaysian-backed outfit returned to the Circuit de Catalunya with re-designed parts and plenty of mileage to make up on their rivals with the season starting in Australia on March 18.
"The car was feeling very good and it's great to bounce back from our dramas to set the fastest time of the day," Grosjean, whose best lap of one minute 23.252 seconds came on the soft tyres and in the afternoon while most others were doing long runs, said on the team website (www.lotusf1team.com).
Technical director James Allison explained that, due to the lost time, Lotus had to compress as much set-up work as possible into the first day and that involved making many short runs.
Grosjean added last week's problem had clearly been solved.
"Now we have to complete a very full test programme this week. The feeling in the team is fantastic and it's like last week's issues never happened," the Frenchman said.
"The chassis is stronger, and all the team is stronger."
McLaren's Jenson Button was fastest in the morning, in 1:23.510, with his team moving their focus away from putting on the mileage.
The team said the first two days would concentrate on pitstop practice and race simulations before attention was switched to the aerodynamic package for Melbourne.
"Having completed more than 2,000 kilometres at Barcelona last week, today was always going to be more about quality than quantity," team manager David Redding said.
"We wanted to drill a little deeper into our understanding of the car and that meant undertaking some bigger set-up changes that wouldn't ordinarily be available to us during a grand prix weekend."
Mexican Sergio Perez was third quickest for Sauber ahead of Red Bull's Australian Mark Webber, although it would be unwise to read too much into the times with teams testing different areas and running with various fuel loads.
Germany's Nico Rosberg was fifth fastest, after completing the most laps (128), in the new Mercedes while Ferrari's Brazilian Felipe Massa was eighth.
Russian Vitaly Petrov stepped into the Caterham at the last moment after Finland's Heikki Kovalainen went down with food poisoning. Despite not having his own race seat fitted, he completed 123 laps. (Reporting by Alan Baldwin; Editing by Sonia Oxley)