Why the impact of FIA’s anti-bouncing metric is hard to judge

Aside from the aesthetics, the biggest visual difference between the older generation of Formula 1 car and the new-for-2022 concoctions was in their vertical movement. Bouncing and porpoising are nothing new in the world of motorsport as a whole but, having mandated flat undertrays since 1983, Formula 1 had spent the preceding four decades in its own bubble – one where porpoising barely figured.

Its appearance and effects therefore blindsided the teams at pre-season testing, where the cars were oscillating so fiercely that their skid blocks were rattling against the track surface and transmitting the impact shock straight to the drivers’ bodies. The teams simply hadn’t seen it coming: not only had a whole generation of engineers grown up in F1 without experiencing the phenomenon, testing restrictions prevented them foreseeing it. Windtunnels are currently capped at simulating speeds of 180km/h; Ferrari, to give one concrete example, has confirmed its car only begins to experience porpoising at 250km/h.

Hasty development work in the early season enabled the majority of teams to tune out the porpoising response caused by the aerodynamic sensitivity of the sub-floor venturi tunnels, either through ride-height changes or by manipulating the airflow underneath the car at certain speeds to eliminate flow patterns causing vertical movement.

PLUS: The mechanics behind porpoising in F1 - and how to fix it

Red Bull proved to be one of the first teams to get on top of it, while Mercedes notably struggled to tame its W13.

Bouncing is a different mechanism, but one still related to the switch to ground-effect aerodynamics this season. The underfloor tunnels require a stable platform to produce consistent downforce; using high spring rates in the suspension ensures the ride height of the car doesn’t change too much around the lap.

But there’s a price to pay for increasing the suspension stiffness. On bumpier circuits, when the unsprung masses (in this case, the wheel assembly) respond to a bump, the suspension yields much less damping through the stiffer spring. That creates a coupling effect, where the sprung and unsprung parts of the car are interlinked and the energy is directed through the bottom of the tub. Hence in Baku Lewis Hamilton had to be helped out of his car because he was in so much pain.

Hamilton suffered back pain after the Azerbaijan GP - just as the FIA moved to install its AOM measures

Photo by: Simon Galloway / Motorsport Images

Hamilton wasn’t the only driver to voice his concerns about the long-term health effects of this car behaviour and the FIA duly announced, ahead of the Canadian Grand Prix, an intent to introduce an “aerodynamic oscillation metric” on safety grounds – thus sidestepping the usual requirement for unanimous agreement from all teams. This metric would be based on the vertical acceleration of the cars, where any continuous cycles could be measured by a sensor and then assessed by the FIA to determine if a car was bouncing excessively.

This process employs an FIA-standard accelerometer already fitted to each car and hooked up to the mandatory accident data recorder. Using the data already gathered from the previous rounds, the FIA set the base metric at 10J/kg/100km as a limit, with wiggle room for each round depending on the circuit. Every car would have its mean AOM calculated from each “eligible” lap of running – which excluded in, out and safety car laps where it isn’t reaching peak performance.

The limit is calculated as a function of the circuit length, the sample time of the accelerometer signal, and the calculated readings themselves, to yield a reading for each car. Any situation where a car exceeds that 10J/kg/100km limit by 20% means that the team can play one of three jokers, as part of an FIA leniency initiative to allow the teams to get their cars into shape. Beyond that, and the FIA has authority to disqualify the driver of that car from the results.

What started as a measure to safeguard driver welfare has therefore become embroiled in the politics of relative performance. Mid-season changes naturally affect some teams more than others, and in ways which are often difficult to understand immediately

This was not universally popular, particularly among the teams who had either fixed their own problems or weren’t suffering from discernible bouncing issues in the first place. Red Bull team principal Christian Horner was among the more vocal detractors of the AOM, standing against the proposal on the grounds that it was a gateway to intrusions on teams’ technical sovereignty.

“When you look at it from a purist’s point of view, it’s not ideal, because it seems that we’re giving more and more influence to the FIA to dictate what your set-up is,” Horner grumbled. “At what point do they say you have to run this rear wing, or a certain ride height? It’s a dangerous avenue to go down.”

Horner later made his opposition to the notion of a bouncing metric more pointed, stating that “there’s an awful lot of lobbying to change the regulations significantly for next year so a certain team can run its car lower and benefit from that concept.”

But even Mercedes, arguably the team that stood to benefit the most from the AOM – and was no doubt the “certain team” to which Horner was referring – wasn’t particularly enamoured with the FIA inserting itself into the debate. As a result, following a stormy meeting with the various stakeholders at the Red Bull Ring in July, the governing body kicked the can further down the road.

Sparks trail from Lando Norris's McLaren at Spa, where the AOM received its belated introduction

Photo by: Mark Sutton / Motorsport Images

Delaying the AOM’s introduction until the Belgian Grand Prix, said the FIA, would give time for the teams to make alterations to their floor and skid block designs, partly since some teams had created modular skid blocks to retract and limit the measurable wear. Plank checks hence became more stringent to ensure nobody continued to shift any wear to other areas of the underbody.

What started as a measure to safeguard driver welfare has therefore become embroiled in the politics of relative performance. Mid-season changes naturally affect some teams more than others, and in ways which are often difficult to understand immediately.

There was a rebellion from a handful of teams, supposedly led by Ferrari and Red Bull, over several of the proposed changes that would roll into 2023. This included a 15mm rise in all floor edges and a rise in the throat height of the diffuser, which would mean that any developments produced throughout 2022 would effectively be voided by the change in dimensions. These changes have since been approved by the World Motor Sport Council.

McLaren wasn’t among the dissenters. Its technical director, James Key, points out that the teams can’t be trusted to make the required changes themselves to lessen porpoising and bouncing, particularly if issues crop up again in subsequent seasons.

“If you imagine you’re the FIA, and you do nothing,” he says, “and it’s still there in ’23 after turning things around and producing new cars based on a lot more knowledge than we had for ’22…

“It’s very difficult to simulate and predict porpoising. We kind of recognise there’s ways of getting rid of it. But it can come back again quickly if you have certain types of development, or increase your downforce. So rather than take that risk, from the FIA’s point of view, it makes sense to try and remove the issue entirely, but also show that we’re taking it seriously and doing something about it after the concerns raised by some of the drivers. You can’t just assume that teams are going to do it.”

Ultimately, despite Red Bull’s trenchant opposition to the changes, the addition of the metric seems to have favoured that team’s package. Following the implementation of the AOM Red Bull’s margin of superiority over Ferrari seemed to grow, and Max Verstappen embarked on a winning streak which netted the drivers’ title with four rounds remaining. Meanwhile Ferrari’s development stalled or even went into reverse as the team rowed back on certain new aerodynamic components.

As the season has progressed, teams have largely dialled out porpoising

Photo by: Lionel Ng / Motorsport Images

Part of this is down to performance characteristics already present in the cars. The RB18 clearly has greater downforce efficiency since it’s been able to cope with running at slightly higher ride heights when the occasion calls for it. Ferrari’s F1-75 was one of the cars more predisposed to porpoising at the start of the year and, although the team had largely ironed it out, the requirement to run more cautious set-ups has proved costly.

Where Ferrari was closest to a victory post-Belgium, when Sergio Perez was being chased down by Charles Leclerc around Singapore’s Marina Bay circuit, it coincided with a loosening in the oscillation metric for the bumpier circuits. Correlation doesn’t necessarily equal causation here, however; the FIA had simply elected to eliminate any spikes over 7G from the metric calculations to ensure that any kerb strikes weren’t skewing the figures. The same rubric was applied at the US Grand Prix at Austin, where the track surface notoriously becomes more bumpy every year.

The bouncing storm that dominated the news agenda in the early stages of this season appears to have abated for now – at least, until someone manages to surpass the FIA’s carefully curated AOM

In fact, it’s hard to discern the actual effect of the bouncing metric on the pecking order. In the case of the floor cuts implemented for the 2021 season, the teams who felt hard done by weren’t shy about airing their grievances – but there have been few such complaints about the AOM. Mercedes still appears no closer to the front two teams, Brazil notwithstanding, and although the likes of Haas and Alfa Romeo have regressed as Aston Martin has improved that can reasonably be attributed to the overall development cycle.

Perhaps those complaints are lying in wait for the end of the season, or for the 2023 changes that will undoubtedly take up valuable windtunnel and simulation time to get right. But the bouncing storm that dominated the news agenda in the early stages of this season appears to have abated for now – at least, until someone manages to surpass the FIA’s carefully curated AOM.

If and when a team does that, and is thrown out of a race, expect all of the arguments to begin anew.

The debate over porpoising has died down for now, but the AOM's impact on proceedings is unclear

Photo by: Andy Hone / Motorsport Images