Top F1 drivers are calling on the sport's sole tyre supplier to improve its wet-weather product.
The now critically injured Jules Bianchi lost control of his Marussia in worsening rain conditions at Suzuka recently when raining on worn 'intermediate' tyres.
Championship leader Lewis Hamilton said drivers often prefer to run on that tyre when it is wet, because the 'full wet' Pirelli is so much slower.
"It is no secret that they are not the greatest wet tyres that I have known," said the Mercedes driver.
...you try to put the intermediate on, taking a lot of risk into account, just because it's the quicker tyre.
"The slick will always be improved, but I guess not so much focus gets put on the wet," he is quoted by the Daily Mail.
"You want a tyre that clears the water and does not force us to go to the intermediate when it is so much quicker, and when it is probably not safe enough to do so," Hamilton added.
Reigning world champion Sebastian Vettel admits the drivers' concerns have been passed on to Pirelli.
"It's definitely something we've passed on already, not just after Japan," he said, reportedly having raised the issue in the pre-race briefing last week in Russia.
"As soon as you've got rid of most of the water (with the full wet tyre), you try to put the intermediate on, taking a lot of risk into account, just because it's the quicker tyre," the Red Bull driver added.
"That's something we need to work on," said Vettel.