The FIA's single-seater director, Nikolas Tombazis has revealed that "four or five" teams had to modify their rear wings in Shanghai following the latest crackdown.

Just days before the second round of the season, after analysing footage from the rear wing deformations, combined to the static deflections measured inside the FIA garage, the sport's governing body concluded that sufficient grounds existed for a tougher test to be introduced from the Chinese Grand Prix.

Article 3.15.17, which was introduced this season, states that if 75Kg of vertical load is applied on either extremity of the rear wing mainplane, the distance between the mainplane and the flap (also known as "slot gap") must not vary by more than 2mm. However the technical directive (TD) sent to all the team following the season opener dictated that henceforth this would be reduced to 0.5mm. However, due to the admitted short notice, only a tolerance of 0.25mm would be added to the new limit for the Shanghai event.

Seemingly the rear wings on the cars of four or five teams did not comply with the new TD.

"I think four or five weren't, and they had to make changes," Tombazis tells Motorsport-Total.com. "I'm hopeful it'll be enough this time."

In terms of using video evidence as well as the physical load tests, he explained: "We continue to use cameras, simply to be safe. But 'safe' is actually a word I want to avoid, because it's a rather complex phenomenon that causes this effect.

"Basically, we mainly use the results of the load tests and combine that with the camera data. That way we ensure we don't miss any tricks.

"Camera images alone would lead us to involve the stewards," he continues. "They're more likely to initiate a more detailed investigation, where we might discover that a team is using non-linear characteristics or a mechanism. Then we'd have reason to report it."

Though none of the errant teams have been identified, Haas and Alpine have both admitted to having to make adjustments, while there are claims that McLaren and Ferrari had to follow suit.

"That shouldn't be seen as arrogance," says Tombazis of the fact that the FIA is adamant that it will continue to monitor the situation even though all ten teams eventually passed scrutiny, "the teams are obviously still trying to get the most out of their cars, and we have to remain vigilant."

As for loopholes...

"Our view is, a car that passes the FIA tests is generally legal, unless there are hidden mechanisms or things based on non-linear properties, temperatures, or similar things. In such cases, we intervene.

"In principle, we would never report a team that has passed the tests to the stewards. But specifically on this issue, and for precisely these reasons, the rules give us the right to conduct additional stiffness tests."