Reactive suspension systems were banned from Formula 1 once it became clear to the FIA that their principal benefit was aerodynamic, AUTOSPORT has learned.
The governing body wrote to teams on Friday informing them that, in its view, the mechanical concepts pioneered by Lotus and Ferrari and being looked at by other teams would be in contravention of the rules if they were used to help the aerodynamics of the cars.
This came despite the initial idea for the hydraulic devices, activated by brake torque, being given the green light as long ago as January last year.
At the time of that initial approval to the then Renault team, it was understood that the devices were purely suspension related and aimed at maintaining ride-height - so effectively nothing more than a sophisticated version of rising-rate springs.
However, with rival teams having expressed an interest in the design, and querying its legality after it was spotted at last year's young driver test in Abu Dhabi, the FIA decided to look much closer at the reactive ride concept.
It is understood that as more details emerged about the Renault and Ferrari systems, both in terms of how they worked and what their benefit was, it became clear that the main advantage of the suspension systems was in helping aerodynamic performance.
The FIA believed that because the systems relied on changes being made to the length of the suspension member as well as unusual movement of the brake calipers - and these alterations helped the aerodynamics of the car - that they were in breach of Article 3.15 of F1's Technical Regulations, which effectively bans moveable aerodynamic devices.
The article states that any part that influences aerodynamic performance "must be rigidly secured to the entirely sprung part of the car (rigidly secured means not having any degree of freedom)" and "must remain immobile in relation to the sprung part of the car."
As well as the potential breach of the aerodynamic rules, it is understood that there was a risk of the reactive ride systems getting challenged under the articles relating to suspension in the F1 regulations too.
Article 10.2.1 states: "With the steering wheel fixed, the position of each wheel centre and the orientation of its rotation axis must be completely and uniquely defined by a function of its principally vertical suspension travel, save only for the effects of reasonable compliance which does not intentionally provide further degrees of freedom."
Article 10.2.3 says: "No adjustment may be made to the suspension system while the car is in motion."
The decision to make a ruling on the reactive suspension systems now removes the threat of the matter building up into a major technical controversy before the start of the season, which could have overshadowed the first race like the double diffuser row did in 2009.
Although the FIA directive states that the governing body views the devices to be illegal, there is nothing stopping teams from continuing to test them and fitting them to the cars for the season-opening Australian Grand Prix - because the final decision on whether they comply with the regulations always rests with the race stewards. But such a scenario is thought to be highly unlikely.