“It was clear from the data that the level of unexpected porpoising would be a concern,” Stella said.
“We realised relatively soon that this level of porpoising was causing a high level of skid-wear energy and this is the reason why both drivers started to take remedial actions in various parts of the circuit.”
McLaren asked the drivers to employ a technique known as ‘lift and coast’ before corners in an attempt to reduce the aerodynamic load on the cars at the end of the straights, when the car is running at its lowest.
Stella said: “Unfortunately, we also saw that, because of the car operating window and the circuit characteristics, most of these actions were not effective enough in reducing porpoising.”
No further explanation as to why this was has been provided.
In current F1 cars, porpoising is caused by a disruption in the airflow under the car.
F1 cars use so-called ‘venturi’ underbodies to accelerate the airflow and create an area of low pressure that sucks the car to the ground to increase cornering performance.
If the underbody airflow is disrupted, it stops working as effectively – or ‘stalls’ – leading to the car jumping up. The airflow then starts working again, sucking the car back down until the same phenomenon is repeated. This usually happens about five times a second.
Stella said the problem was caused by “an anomaly in the behaviour of the car, rather than it being the outcome of an excessive or unreasonable chase of performance”.
The safety margin applied had been “negated by the unexpected onset of the large vertical oscillations, which caused the car to touch the ground”, he said.
Stella said the amount of excessive wear on the metal skids was “relatively minor”.
On Norris’ car, two of the skids were illegal – one at the front by 0.12mm and one at the rear by 0.07mm.
On Piastri’s car, three of the skids were worn lower than the 9mm permitted minimum thickness – two at the front by 0.04mm and 0.26mm and one at the rear by 0.1mm.
Stella said: “Unlike sporting or financial rules, there is no proportionality in the application of penalties for technical regulation infringements.
“The FIA itself has admitted that this lack of proportionality should be addressed in the future to ensure that minor and accidental technical infringements, with minimal or no performance benefits, do not lead to disproportionate consequences.”
Governing body the FIA has been approached for comment.
Stella said he did not expect the problem to recur at this weekend’s Qatar Grand Prix.
Stella said: “The conditions we experienced last weekend and which led to the onset of porpoising and excess of grounding, compared to what was expected, are very specific to the operating window of the car in Vegas and the circuit characteristics.
“We have a well-established and consolidated way of setting up the car and we are confident that this will lead us to an optimal plan for the coming races, starting from the Lusail International Circuit.”
