Renault have been struggling to find pace in testing

Renault won back-to-back titles on Michelins but its decision to quit left Bridgestone as the only supplier.

"We have not unlocked the secret of getting performance out of the tyres," said head of engineering Pat Symonds.

"We are not worried but when you are not on top of the pile you have to be honest enough to admit it."

Renault were off the pace in this week's testing in Barcelona, with Giancarlo Fisichella ninth fastest ahead of team-mate Heikki Kovalainen in 10th.

Although winter testing does not always provide an accurate reflection of a team's potential, Symonds saw enough to realise more work needed to be done to adapt to the Bridgestones.

Our objective was to learn our lessons by the time we reached Melbourne - we are not in Australia yet Pat Symonds

"We seem to be several tenths away from the fastest runners in most conditions, on the first laps and long runs too," he said.

"We know what we want to do to find the performance; we need to start getting the most out of the tyres and push even harder on all our traditional development paths.

"But this is winter testing and you cannot be sure of the fuel loads other people are running."

McLaren, who now have Renault's double world champion Fernando Alonso on their team, have been impressive in testing.

Symonds has been keeping a close eye on his rivals but is confident Renault will improve ahead of the season-opener in Melbourne on 18 March.

"McLaren and Ferrari have been pretty equal at the front and BMW are right up there too," said Symonds.

"Our objective was to learn our lessons by the time we reached Melbourne. We are not in Australia yet, and we haven't learned all our lessons either."