Australian GP: Mercedes' Rosberg and Hamilton still chasing set-up

Despite being comfortably quickest on the opening day of action in Melbourne, the pair confessed that they did not feel totally comfortable with how things were progressing.

It is a repeat of the issues they had in testing where, despite strong pace, they found it hard to get the new W06 operating how they wanted it to.

Hamilton, who was beaten by Rosberg in both Friday practice sessions, said: "The car's not ready yet. We've got some work to figure out the set-up. It's not perfect balance-wise."

Rosberg has no doubts that the fight for victory in Australia will be between him and his team-mate, and that getting the right set-up is therefore going to be crucial.

"The challenge as always is against Lewis," he said. "He was very quick again today, but I'm still searching for the perfect set-up and that's what it's going to come down to, I think.

"I'm not 100 per cent happy with the car set-up and that's what I'm working for.

"It's really difficult because there are infinite set-up parameters that we could use: is it mechanical, is it aerodynamic?

"It's very difficult sometimes even to decide which one to use to improve the car."

Despite the set-up woes, the drivers were overjoyed with the speed of the Mercedes - which appears to be a step clear of the opposition.

Hamilton added: "The guys at the factory have done an incredible job this winter. To arrive here and for the second year in a row to have a competitive car is an amazing feeling.

"As drivers we want to push the car and get to the limit. And it's our job to try to keep our heads down and try to maximise the set-up."