A failed sensor on Oscar Piastri's car meant McLaren could not measure the oscillations that ultimately led to its double disqualification in the Las Vegas Grand Prix, its analysis has revealed.
Lando Norris finished second on the road in the Vegas race with Piastri set to be classified fourth before both drivers were disqualified as their cars were found to have excessive skid wear on the plank beneath the floor.
Both cars being in breach of the rules helped Piastri in one sense as it negated the six-point gain Norris was going to benefit from, but it allowed race winner Max Verstappen to draw level with Piastri in second place in the championship - and cut his gap to Norris from 42 points to 24.
McLaren's immediate reaction after the disqualification was to apologise to the drivers and promise an investigation, while explaining that it had been caught out by excessive porpoising in the Vegas race.
These aerodynamic oscillations had not been expected based on the limited amount of dry running that was available during practice.
What McLaren's revealed
In a first explanation of its findings that McLaren shared on Thursday, when both drivers will face the media in Qatar, team principal Andrea Stella did not reveal why McLaren suffered excessive porpoising – only that it "was exacerbated by the conditions in which the car operated during the race".
Stella said it was already clear from the "early laps of the race" that this would be a concern, hence the situation that unfolded late on when Norris began to lift and coast a lot in the final laps.
This was an ultimately futile effort to try to protect the plank at the end of the straights on the fastest parts of the circuit, as reducing the speed there should mean the rear of the car was not pulled as close to the track surface.
Piastri did not engage in the same methods to the same degree, and Stella revealed that McLaren was "able to monitor the situation better on Lando's car using telemetry data".
"It was made more difficult on Oscar's car, after we lost one of the sensors we use to establish the level of grounding," said Stella.
"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.
"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."
Cause still mysterious
Interestingly, Stella also said that reducing the speed "was only effective in some parts of the track but in others was actually counterproductive".
That, along with why McLaren suffered porpoising in the first place and what specifically exacerbated it, is still uncertain.
Running low is a well-established necessity in these cars, hence the porpoising phenomenon that emerged as a major factor early in the ruleset in 2022, and street tracks such as Vegas are inherently bumpier and more challenging on plank wear than most circuits.
But no other team fell foul of excessive plank wear despite all cars in the top 10 being checked - and McLaren felt it had not taken "excessive risks in terms of ride height" either.
"We also added a safety margin for qualifying and the race, compared to practice, in terms of clearance to the ground," said Stella.
"However, the safety margin was negated by the unexpected onset of the large vertical oscillations, which caused the car to touch the ground."
As this weekend's race in Qatar takes place on a very different type of circuit, McLaren does not expect a repeat of something "very specific to the operating window of the car in Vegas and the circuit characteristics".
However, Stella said what happened has provided "some useful information about the operating window of the car and the porpoising regime" and praised the reaction from the team at its Woking factory to what caught McLaren out.
Team orders question looms
The mix of medium and high speed corners at the Lusail track is expected to suit McLaren as Norris aims to wrap up the title before the Abu Dhabi finale.
Piastri is still in contention but is on a poor run of form for various reasons and the proximity of Verstappen will inevitably revive questions about whether McLaren should focus on Norris to ensure it wins both championships - having gone to great lengths to treat both drivers equally all year.
But Stella said "there is no reason to do so".
"We have always said that as long as the maths does not say otherwise, we would leave it up to the two drivers to fight for their chance at the final victory, and that is how it will be in Qatar," said Stella.
"Let's not forget that if someone had told us at the start of the season that we would find ourselves in this situation with two races to go, we would have signed up for it.
"Now we are going to fight for the double world championship with confidence and awareness of our strength."
