The intrigue over high-tech suspension systems pioneered by Mercedes has been around for several years, but the trigger for the latest row over what is and isn't allowed can be traced back to the Abu Dhabi Grand Prix.
According to sources, an overheard radio conversation between Daniel Ricciardo and his Red Bull pitwall about car set-up and the impact of the suspension on aerodynamic performance left some rival teams suspicious that there was more to these devices than originally thought.
In particular the idea of the suspension being used primarily to help aerodynamics prompted Ferrari to take action and write to the FIA to clarify exactly is and is not allowed.
Such a request for clarification to F1 race director Charlie Whiting is common – as it offers teams an opportunity to discern the legality of designs they intend to pursue, the chance to better understand the ones used by their rivals, or highlight to the FIA where others might be operating in grey areas.
In this case, Ferrari has queried the use of more complex systems than the one that Mercedes has legally put to good use – primarily one that stores energy that can be then be released to improve the car's aerodynamic platform over the rest of the lap when it is better needed.
But have teams like Mercedes and Red Bull been doing it already, were they planning on doing it for 2017 – or is Ferrari's bid simply to cut off an avenue of expensive development before it pushed full on with its own concept?
The intrigue surrounding the pre-Christmas technical directive from Whiting suggesting trick suspension systems that stored energy would be illegal comes in the wake of what F1 saw teams do with FRIC (Front-to-Rear-InterConnected) systems up until their effective ban ahead of the 2014 Hungarian Grand Prix.
The potential aero benefits of a clever suspension system can even be traced back to Renault's famed mass damper during Fernando Alonso's title years – and in recent years it was Mercedes that was at the forefront of the FRIC technology.
At the time, the removal of their concept seemed like a good way to peg back the Silver Arrows, but such was the team's commanding position and the advanced state of the systems run by those around it that it meant there was very little effect on the pecking order.
In F1, knowledge is never unlearned though – and with FRIC gone, resources were shifted to replicate the peripheral advantages it gave – as teams set about creating a similar effect, albeit without the hydraulic connection front-to-rear.
Much of the work done by FRIC revolved around heave - the vertical displacement of the car. Being able to connect the front and rear also helped to stabilize the car's roll through corners, improving aerodynamic stability as a consequence.
It is natural that the teams would have the FIA believe that the reason for these systems/subsystems was to improve tire performance and life, enhancing mechanical grip with an emphasis on increasing the contact patch.
However, while this is true, a chief motivation is always going to revolve around improving aero, with a more stable platform able to provide the team with the ability to hone in on aggressive solutions.
The heave element is by no means new in Formula 1, but the way in which teams are using them is far beyond what would previously have been considered ordinary.
The heave element provides stiffness at speed to improve how the car reacts to aerodynamic load, stabilizing the car and ensuring that it performs optimally as the airflow acts on the various surfaces.
At lower speeds the heave damper is decoupled, giving the driver the type of compliance he needs. But it is during transient conditions that the designers have had to find more and more performance, as discerned to us in an end of season interview with Mercedes technical chief Paddy Lowe.
In the interview with Giorgio Piola, Lowe was open about the aerodynamic benefits of the suspension system Mercedes ran at times in 2016.
Here is what he said.
Q: Is the use of a hydraulic heave damper used to achieve what was done with FRIC?
Paddy Lowe: "It's left us just trying to do things one end at a time and design spring and damper systems that will react to load in a more complex manner. A spring classically was linear, [but now] we are playing with far greater and more complex ranges of non-linear compliance.
"That's allowing us to play games with getting the aero platform exactly where we want. It's more difficult to do than it was with FRIC, but it's the same thing really."
Is it easier to achieve with a hydraulic damper rather than a conventional springed set-up?
PL: "It's about maintaining balance at different aspects of the circuit, different cornering speeds. Getting the best from the aero platform and best balance from high speed to low speed and indeed through different phases of the corner. All the teams are playing more tunes than ever they used to. Our suspension therefore becomes more complex year on year. We've not doing anything particularly tricky, it just gets more complex."
"If drivers from the past got into these cars they'd have their mind blown by how well balanced they are. We can set the car up with far more precision – and the degree to which we're tailoring aero and mechanical platform almost corner by corner even within the corner and brake balance, all these different things get a car where you can get to a certain point in the weekend where the driver is saying there's nothing to tune. It's a perfectly balanced car.
"Of course It's not quite like that – because the tire is moving around – but compared to how it was say 20 years ago, when you had to take a really very crude approximation of getting a balance at as many corners as possible, whilst accepting the others would be rubbish."
The crux of Ferrari's request for clarification centres around the recovery and storage of energy to be used at a later time to extend a spring seat or other parts of the suspension assembly.
This infers the use of hydraulic accumulators that are designed to store and dispense energy under certain conditions, creating a sort of high pressure hydraulic computer. This fluid logic system would rely and react to inputs, as the car undergoes various conditions around a lap.
Think then of the heave element and ancillary remote accumulators as a three-dimensional map, rather than just the cylindrical elements they outwardly appear to be - with small and large chambers interspersed to accommodate the various inputs, loads and conditions.
Imagine that as an F1 car approaches a corner - the driver will commence the braking phase, at which point the weight of the car should shift forward and the aerodynamic loads are altered.
If a team fully understood the inertia from a mathematical perspective you could model a reactionary response from the front and rear suspension that would keep the platform of the car within an acceptable tolerance, improving both mechanical (including the tire's response) and aerodynamic performance.
The knock-on effect is that the driver can carry more apex speed and will accelerate out of the corner earlier than is ordinarily the case.
Red Bull advances
There were rumours last year that Red Bull had also gotten particularly advanced in this area – with it able to have a car with a high rake for aerodynamic benefit in the corners but then sank down at the rear on the straights to minimise drag from its wings.
Rake is something that must be looked at from a conceptual point of view, because adding a Red Bull or McLaren level of rake to the Mercedes isn't going to see an immediate rise in performance.
Of course it's an exceptional tool to draw from, but simply cranking up the rear of the car will not work if all of the other aero surfaces are not in tune with it.
The Red Bull philosophy revolves around perfecting aerodynamic structures that emanate from the front wing and tie in with the floor and diffuser. The obstacle to its performance is always the tires, with neutering the airflow that is spilt from them critical in creating the necessary rear end downforce to complement what's going on ahead.
The use of a well tuned HPC (Hydraulic Pitch Control) suspension system, as some of the teams have called it, is something that has been part of Red Bull's success throughout 2016 as it overtook Ferrari.
For a team that usually had an abundance of aerodynamic updates at each Grand Prix, Red Bull was surprisingly quiet on that front last season. Instead, at each GP it honed its set-up, perhaps trialing a different front or rear wing on occasions, in order to maximize the car's operating window.
While it's understood that it sacrificed some of its resource early on to focus on the 2017 car, it's perhaps its mooted acquisition of a full chassis dynamometer that has seen it make further strides.
The VTT (Virtual Test Track) as it is known replicates its car in every aspect and allows it to run the car in the simulator loop, including the power unit.
Suspension actuation is also conducted and helps the team to make some decisions about the set-up, both aerodynamically and mechanically, before getting to the track.
This has led to what has been interpreted as a hunching over of the car on the straights, causing a drop off in downforce and drag and boosting straightline speed, helping the team to overcome some of the deficit of its the Renault power unit.
Red Bull's use of HPC is different in its approach to Mercedes, but both systems are aimed at improving the relationship between all aspects of the chassis to improve overall lap time.
So when Ricciardo was overheard on the radio in Abu Dhabi, talking in detail about the impact of suspension settings, did that trigger a new thought process in Ferrari's head?
Legal or illegal?
Ferrari's move has obviously led to the pointing of fingers about what Mercedes and Red Bull are up to – but only those two teams know exactly what they have and have not been doing.
The debate about what is and is not allowed is still ongoing with the FIA – but from Mercedes' perspective at least, it remains convinced that the system it ran when needed in 2016 does not fall foul of the FIA's interpretation of a moveable aerodynamic device so there is no impact from the latest ruling.
Indeed, the feeling is that Ferrari's clarification could have more of an impact on what Red Bull may have been planning for 2017 as it bids to push its suspension system on even further.
That the matter is not closed yet shows that some teams are on the limit of what is and isn't allowed – and that leaves Ferrari in a bit of a dilemma.
For does it now push on with its own trick system, does it accept Whiting's interpretation, or does it keep fighting and open up the prospect of a protest at the Australian Grand Prix?
Cast minds back to 2009 when the double diffuser row kicked off and Ferrari's belief that a protest to the stewards in Melbourne about them would be enough to get rid of them.
Ferrari may feel like it has dealt a blow to the opposition in Whiting's ruling, but nothing is ever that simple in F1.
One thing is for sure though - that ahead of the all-new cars coming for 2017, the suspension issue is likely to be the first of many skirmishes between teams as they keep a close eye on what their rivals have been up to.
Co-author: Matt Somerfield, Assistant Technical Editor