Lotus head of trackside operations Alan Permane has claimed that driver Kimi Raikkonen feels "unsettled" with the front end of the Pirelli construction.
Raikkonen has been out-qualified by his teammate Romain Grosjean six times in the last eight races of the Formula 1 calendar.
"He doesn't like the front end," Permane told AUTOSPORT. "He doesn't like the turn in.
"It is not sharp enough for him, but, if you try to sharpen it up too much, you then lose the rear.
"It has just unsettled him a little bit. But he is getting to grips with it. There is no stopping Romain at the moment, that is for sure."
Raikkonen has agreed to leave Lotus and return to Ferrari for the 2014 campaign.