Pirelli motorsport director Paul Hembery said at the British Grand Prix that his company was open to developing new tyre sizes in the future .
Motorsport director was not convinced 18 - inch tyres were big enough .
Pirelli motorsport director Paul Hembery said at the British Grand Prix that his company was open to developing new tyre sizes in the future , although he was not convinced 18 - inch tyres were big enough .