Old BMW better balanced says Heidfeld
Despite the German squad targeting a maiden victory this season, the 2008 car has usually been outpaced by its predecessor, the F1.07, on Spanish test circuits so far.
Heidfeld, 30, revealed that the problem is the car's balance.
"We have understeer and oversteer, and too much of both," he is quoted as saying by the German magazine Auto Motor und Sport.
Heidfeld refused to comment on whether he thought the 2007 car, which was F1's quickest racer excluding the Ferrari and McLaren last year, is better than its successor.
"All I can say is that the old car was better balanced," he admitted.
"I have to drive differently than I would like, but I don't want to say any more about it."
He insists that BMW engineers are busily working on improving the F1.08.
"We think we have identified the problems," Heidfeld explained.
"Maybe we will not see all the solutions at the next test, but the engineers assure me that it will be solved by the first race in Melbourne.
"I have the feeling that the matter is under control, but in this business you can never be 100 per cent sure."