The Red Bulls of Sebastian Vettel and Monaco pole-sitter Mark Webber are understood to be running with floors featuring a ‘hole’ in the surface of the step plane directly in front of the rear tyres.
The location of the hole is said to be the main cause of concern for a number of Red Bull’s rivals, even though the FIA, motor sport’s governing, declared the device legal in Bahrain, a race won by Vettel.
The matter could come to a head today should a rival team elect to lodge a protest, with McLaren, Mercedes and Ferrari seemingly the most aggrieved.
But Red Bull team principal Horner said: “There was a bit of a fuss after the Bahrain race but it was clear the car complied. We sought clarification after that, but there is no doubt the car is fully compliant.
“As I say, we’re totally comfortable with the car, that it complies with the regulations and we’re not going to change it.”