Ross Brawn says aero staff changes were key to Mercedes' F1 slump

Mercedes, which took over the world champion Brawn squad in late 2009, scored its first F1 race win as a constructor since 1955 when Nico Rosberg dominated the Chinese Grand Prix from pole position.

By the halfway point of 2012, Rosberg lay sixth in the championshp, only 34 points behind Red Bull's Sebastian Vettel.

But the squad's form suffered during the second half of the year, Rosberg eventually trailing world champion Vettel by 189 points and Michael Schumacher's sixth place in Brazil its only points finish from the final six grands prix.

Team principal Brawn said that the departure of head of aerodynamics Loic Bigois, coupled with a change in windtunnel philosophy while the team experimented with Coanda exhausts and double DRS, also played a major influence.

Brawn said: "We made a decision to change the structure of the aero group. We had to wait for [new aero chief] Mike Elliot to join us because we had a notice period he had to fulfil at Lotus.

"We concluded the situation with Loic and there was a gap that we didn't fill very well."

"On top of that we were doing the transition from 50 per cent to 60 per cent models in the windtunnel, and there were a lot of other things in the aero group as well. It did have an impact."

Brawn said that the shift to 60 per cent models was necessary to increase the amount of technical data it could extract from Pirelli's tyres.

"Our conclusion was that we would get a much more representative tyre at 60 per cent than at 50 per cent," he added.

"Pirelli have to make 50 per cent and 60 per cent windtunnel tyres. There are only two teams that are still doing 50 per cent.

"Even with Pirelli's best efforts, they're going to be getting better feedback about 60 per cent tyres than 50 per cent. So we wanted to make the move.

"The other thing that has happened over the years is that you're putting more and more equipment inside the windtunnel model to measure, monitor and check. We just ran out of space in the 50 per cent model.

"There were things that we wanted to do that we couldn't do, and we needed the 60 per cent model to accommodate those features. Sixty per cent is the legal limit you can go to, there is no further step we can make."