Dual Axis Steering (DAS)

Pushing and pulling the steering wheel along its column changed front-wheel toe angle on the move, letting the driver run toe-out for cornering grip and toe-in on the straights for lower drag and better tyre temperature.

Article 10.4.1 banned realigning more than two wheels. DAS realigned exactly two. Article 10.2.3 governs suspension, and DAS is a steering system, not a suspension one. The car fell between two articles that each assumed the other covered it.

Front tyre temperature management, particularly on out-laps and behind the safety car. Never isolated as a lap-time number in public data.

A new Article 10.4.2 for 2021 restricting the steering wheel to a single rotational degree of freedom, with a strictly monotonic relationship between wheel angle and steered angle.

The most-asked ban question anywhere. It is also the cleanest example of the rulebook's real structure — DAS was legal because two articles each stopped just short of it, and the fix was one new sentence that closed the gap between them.