Bridgestone fears that drivers could run out of intermediate tires if the Belgian Grand Prix takes place in mixed weather conditions.
With drivers limited to just four sets of intermediate tires for the whole of a race weekend, Hirohide Hamashima, Bridgestone's head of motorsport tire development, thinks that the current situation is marginal after teams used up one set during Friday practice.
"In FP2 I was very surprised that everybody wasted one set of intermediates," said Hamashima, who thinks the worst case scenario is for mixed weather. "The majority of the opinion is that the intermediate performance was going down after five to 10 laps.
"I am very worried that if they start the race with the intermediate and then rain comes 10 laps in, performance will be not enough. So then tire management will be very, very crucial."
Hamashima said that in normal circumstances the wet weather tire limit of three sets of wets and four sets of inters is more than enough - but that the mixed weather on Friday had caused a unique situation.
"A few years ago [Flavio] Briatore complained so strongly that there weren't enough wet and intermediate tyres, but we explained to everybody that the past data showed that three sets of wets and four sets of intermediates are enough. That was until yesterday. For this weekend now I don't know."
Former world champion Lewis Hamilton was one driver who reckoned that the tire rules could need revisiting, after teams sat in the garage for a lot of Friday to conserve tires.
"Well it would be better for the fans if we had more tires and could go out more and test, because that's what we're here to do," he said. "It feels a little bit silly to be here, prepared all this time, and then just sit in the garage for the whole of Friday.
"I liked the old days where you could go out and practice and practice and practice. That's what it was about."