Heidfeld: Best car, biggest struggle in F1.

Nick Heidfeld has admitted that he was beginning to get very frustrated by the problems that saw him fall away from BMW Sauber team-mate Robert Kubica towards the halfway point of the Formula One season.

The German started brightly, with second place in the season-opener at Melbourne, but, while Kubica picked up his game to win in Canada and take the lead of the world championship as a result, Heidfeld's pace dropped off, particularly in qualifying. Another second place in Montreal was sandwiched between a DNF in Monaco and 13th in France - and was the result of a typically unpredictable Canadian Grand Prix - before the veteran began to feel like he had turned a corner with the set-up of his F1.08.

Although his Magny-Cours performance did not suggest as much, Heidfeld insists that the turnaround began in qualifying for the French Grand Prix, before picking up momentum at the Silverstone group test and culminating in a third runners-up spot of the season at the following weekend's race at the British circuit.

"In the beginning, I did hope there would be one big thing I would change and suddenly, 'boom', it would work," he revealed, "Unfortunately, that was not the case. It was hard, with a lot of small things coming together, but I think I have not discovered all of them yet, so I think there is even more potential to make more progress.

"Already in Magny-Cours, I made some good progress. Although I was not quite making it into Q3, I was just a few hundredths off Robert, who obviously gets on with this year's car very well.

"It has been a process over a couple of months, looking at the problem and finding the problems I had, working out with the engineers and doing some changes on the set-up, mainly on the mechanical side, as well as doing some changes on tyre preparation and changing my driving style a bit. All that has helped me to improve my qualifying performance over one lap.

"My race performance already worked quite well, and the last few races have shown that it is probably going in the right direction, having two second places in the last three races. I hope it continues like that."

Heidfeld admitted that he was beginning to get frustrated at not being able to generate sufficient heat in his Bridgestones to produce a decent qualifying slot, with the consequent knock-on to his race results.

"It was not depressing, that's the wrong word, but it was very hard knowing that we have a very strong car - probably the strongest car I have ever been in - and then struggling the most I ever have in F1. I think, normally, I've most of the time been able to maximise the potential of the car, but then, this year, unfortunately not.

"It was quite difficult, but it was great seeing the team behind me and it was good finding a couple of solutions and seeing that all the work I've done and we have done as a team started to pay off."