Insight: Why the FIA believes Mercedes' steering device is legal

Formula 1's second day of pre-season testing has been dominated by intrigue surrounding the Mercedes 'Dual Axis Steering' (DAS) system.

But while the clever trick of adjusting the toe angle of the front wheels through steering wheel movement left some questioning how it could be allowed, the FIA is comfortable the design is fully in compliance with the regulations.

It is understood that Mercedes has been in detailed correspondence with motor racing's governing body about the idea for some time and has proceeded to feature it on its W11 only because the opinion of the FIA is that it is allowed, rather than risk a disqualification from the Australian Grand Prix.

Autosport has learned that the central matter for the FIA is the grey area in the regulations between what are suspension components and what are steering parts of the car.

The regulations are clear that suspension changes made when the car is in motion are not allowed.

"No adjustment may be made to any suspension system while the car is in motion," states Article 10.2.3 of F1's technical regulations.

If in the FIA's view the changes made to the toe angle were altering the suspension of the car, the DAS would be outlawed, but instead its view is that the DAS is merely another way of 'steering' the front wheels.

In terms of what is allowed in terms of steering, the rules are not as restrictive.

Article 10.4.1 of the technical regulations states: "Any steering system which permits the re-alignment of more than two wheels is not permitted."

As the Mercedes system only adjusts the toe of the front wheels, it is fully in compliance.

Moreover, nowhere in the regulations does it state that the wheels can only be turned on one axis - nor that the two front wheels must change angle at the same rate.

That means that Mercedes changing the angle of the front wheels to alter the toe is allowed because there is no regulation that states it cannot be done.

The only stipulation regarding such a DAS system is that it cannot be done through power-assisted means - as the power-steering of the car has to comply with a regulation that states: "No such system may carry out any function other than reduce the physical effort required to steer the car."

The Mercedes steering system must also have have had to comply with crash tests.

Rival teams are well aware that Mercedes has exploited an area in the rules that has not been tested in this way before - and has got a head start in designing, building and testing the system.

Since its ultimate legality can only be proven by race stewards if there is a protest, the question is now if other teams begin work on their own solutions immediately, or wait for clarity in Melbourne with a potential challenge.

At a time when all outfits are already juggling resources with the 2021 F1 revamp on the horizon, having to throw extra focus in to coming up with a DAS system will almost certainly be a major disruption for everyone that elects to create one.