Heidfeld unhappy despite progress

The German took ninth in the afternoon session but was still dissatisifed with the car's handling.

"We are making progress, although I'm not satisfied with the balance of the car yet," he said. "It is not just as I want it to be - neither on a single lap nor on a long run. You can feel the tyre compounds are now more similar to each other than they used to be, but I'm afraid the tyres are still not really good."

His team-mate Robert Kubica continued to struggle, managing only 14th place in the second session - although he had been 11th earlier on.

"The car in the morning session felt good straightaway," said the Pole. "In the first run especially I was quite happy. When there was more rubber on the track we tested some new parts and a modified front wing. In the afternoon I was not too happy with the car."

The team's engineering boss Willy Rampf said practice had only been a first hints of the development parts' potential, and that there should be more to come.

"We used some new parts today, which prior to this had only been tested in the windtunnel," he explained.

"Therefore we put a lot of emphasis on working on the set-up of the car and finding a good baseline. I think we were able to make a small step forward."