Pirelli has denied claims its mid-season tyre specification change will add yet another kilogram to the already-hefty weight of this year's F1 cars.
Teams tested the updated tyres in practice for the Spanish GP - and they are debuting this weekend at Silverstone.
Pirelli argued that the changes are to respond to higher-than-expected downforce levels.
"In Barcelona, the (new) tyres were already 800 grams heavier," said Mercedes driver George Russell, a director of the Grand Prix Drivers' Association.
"And the tyres we're using here are even 1.1 kilograms heavier than what we had in Austria last week," he added.
According to Germany's Auto Motor und Sport, Pirelli has denied that claim - insisting the new tyres actually add less than half a kilogram of extra weight.
It is yet to be seen if the new tyres shake up the pecking order at all, especially for the teams who have been struggling with excessive wear.
"I think it will be important to evaluate and understand how much difference the new tyres make on the degradation," said Ferrari's Charles Leclerc ahead of the British GP.
"We don't know if it will be a benefit or not."
