Both drivers suffered left rear blow outs in the Baku race, with the initial suspicion pointing to debris being the cause of the incidents.
This theory was boosted by the fact that other cars were found to have suffered cuts on their tyres during the red flag period triggered by Verstappen’s incident.
In a bid to get to the bottom of what happened, Pirelli flew the tyres back to its Milan headquarters for a detailed analysis in its laboratories.
On Tuesday, the Italian tyre company issued a release making it clear that the failures were not caused by a production fault, wear nor delamination.
It went on reveal that the blow outs were instead caused by a circumferential break on the inner sidewall of the tyres, rather than being the result of a cut from debris.
The statement suggested that the breaks in the sidewall were likely caused by the ‘running condition of the tyre’ – which is probably related to either tyre pressures or the temperatures they were run at.
“This analysis also took in the tyres used by other cars in the race, which had the same or a higher number of laps on them compared to the ones that were damaged,” it said.
“The process established that there was no production or quality defect on any of the tyres; nor was there any sign of fatigue or delamination.
“The causes of the two left-rear tyre failures on the Aston Martin and Red Bull cars have been clearly identified.
“In each case, this was down to a circumferential break on the inner sidewall, which can be related to the running conditions of the tyre, in spite of the prescribed starting parameters (minimum pressure and maximum blanket temperature) having been followed.”
Lance Stroll, Aston Martin AMR21, crashes out of Qualifying
Photo by: Mark Sutton / Motorsport Images
F1 teams are currently only required to run tyres at a minimum tyre pressure when they are first fitted to the cars, as there is no requirement for them to maintain pressures once a car is out on track.
This means that the door is open for teams to find ways to lower the pressure once checks have taken place, but such a reduction in pressure means the tyre is put under more stress.
Pirelli revealed that new pressure and tyre blanket protocols were to be put in place to ensure there could be no repeat of the Baku problem, with teams having already been informed by the FIA of what new processes must be followed.
The statement added: “As a result of this analysis, Pirelli have submitted their report to the FIA and the Teams. The FIA and Pirelli have agreed a new set of the protocols, including an upgraded technical directive already distributed, for monitoring operating conditions during a race weekend and they will consider any other appropriate actions.”
Red Bull has since responded to the findings and insists it ran its tyres within Pirelli’s parameters.
“We have worked closely with Pirelli and the FIA during their investigation into Max’s tyre failure on lap 47 of the Azerbaijan Grand Prix and can confirm that no car fault was found,” the Red Bull statement read.
“We adhered to Pirelli’s tyre parameters at all times and will continue to follow their guidance.
“We are grateful that following the weekend’s high speed impacts no drivers were injured.”