Red Bull's protest against Mercedes' dual-axis steering (DAS) system has been rejected after the stewards of the Austrian Grand Prix declared the innovation legal.
The legality of the novel solution, which is unique to Mercedes, has been debated since it was first spotted by rival teams during preseason testing in February. The system is designed to change the alignment of the front wheels when viewed from above to either point inward or outward -- known as the toe angle -- and is controlled by the driver moving the steering wheel backward or forward.
Although DAS has a direct impact on the handling characteristics of the car, it is thought that its main benefit is to condition the tyres by changing their alignment so that the rubber scrubs across the surface of the track and generates heat in the tyre. The system was in use by Lewis Hamilton and Valtteri Bottas during Friday practice for the season-opening Austrian Grand Prix, but only during out laps and in laps, and not on flying laps when the drivers set their quickest lap times.
In order to gain clarity on the system prior to qualifying, rivals Red Bull lodged a protest on Friday evening claiming the system was in breach of Article 3.8, which outlaws movable aerodynamic devices, and Article 10.2.3, which prohibits "changes to any suspension system while the car is in motion."
Ultimately, the stewards -- who conducted their investigation via videoconferencing -- had to determine whether DAS should be considered part of the suspension, and therefore illegal, or part of the steering, and therefore legal.
Red Bull argued the system was clearly aimed at changing the toe angle, which is usually adjusted only in the garage via suspension settings and not via the steering system. They claimed the car's steering clearly worked without DAS, as the Mercedes drivers did not activate it on the laps on which they set their fastest times, and therefore it must serve the purpose of changing the suspension settings to condition the tyres.
Mercedes countered that claim by saying DAS plays no role in suspending the car and simply changes the alignment of wheels -- like a conventional steering system -- but just so happened to turn them in opposite directions rather than in the same direction. It also pointed out that a car's toe angle changes the responsiveness of the steering and is therefore part of the steering.
Having heard both sides of the argument and deliberated for 6½ hours, the stewards deemed that DAS would be illegal if it were not part of the steering system, but because its function is to align the wheels and there are no rules limiting the ways in which the steering wheel can be used to do that, it was in fact part of the steering system and therefore legal. They also confirmed that DAS was mechanically operated and part of the steering system but would still be legal if it were hydraulically operated.
The full statement from the stewards, including the arguments made by both teams, can be found here.