Pirelli is planning some fundamental changes to its tyres for the 2012 season, test driver Lucas di Grassi has revealed.
Brazil's Globo Esporte spoke to the former Virgin race driver prior to his next outing in the 2009 Toyota scheduled for early next week at Jerez.
"Only a few things need to be improved," said di Grassi, who is now Pirelli's main test driver on the heels of Nick Heidfeld and Pedro de la Rosa.
"The first is the 'marbles', and the engineers are trying to reduce them," he said.
"Another is that the tyres are not rubbering-in the tracks as much because the chemical bond between the rubber and the asphalt is too weak."
Di Grassi also said Pirelli is working to widen the 'operating window' of the tyres, with teams like Ferrari for example struggling massively on the hard compounds.
"The performance difference with the hard tyre can be too big between the teams," he acknowledged.
"The aim for next year is to improve a bit, and a bit more for the next year, because you can't make drastic changes."
Di Grassi also said Pirelli has developed a very durable compound.
It's a type that lasts an entire race, like Bridgestone
"It's a type that lasts an entire race, like Bridgestone. But this is not a proposal for Formula One today."
As for his own future, the 26-year-old said returning to the F1 grid is the main aim, but staying with Pirelli or switching to Indycars are also options.
"The plan is to return to Formula One but it would depend. It would have to be shown there is potential for long-term development.
"If it's the conditions I had in the first year (with Virgin), then no," said di Grassi.