Both riders suffered blowouts to the left rear during the Baku race, with initial suspicions pointing to debris behind the incidents.
This theory was reinforced by the fact that other cars suffered cuts to their tires during the red flag period triggered by the Verstappen incident.
In an effort to shed light on what happened, Pirelli returned the tires to its Milan headquarters for detailed analysis in its labs.
On Tuesday, the Italian tire company issued a statement making it clear that the failures were not caused by a production defect, wear or delamination.
He then revealed that the bursts were more caused by a circumferential rupture on the inner sidewall of the tires, rather than a cut of debris.
The statement suggested that the sidewall ruptures were likely caused by “the tire’s working condition” – which is likely related to the tire pressure or the temperatures at which they were used.
“This analysis also took into account the tires used by other cars in the race, which completed the same number of laps as or greater than those which were damaged,” he said.
“The process established that there were no production or quality defects on any of the tires; there was also no sign of fatigue or delamination.
“The causes of the two failures of the left rear tires of the Aston Martin and Red Bull cars have been clearly identified.
“In each case, it was a circumferential rupture on the inner sidewall, which can be linked to the operating conditions of the tire, despite the respect of the prescribed starting parameters (minimum pressure and maximum temperature of the blanket).
Lance Stroll, Aston Martin AMR21, exits qualifying
Photo by: Mark Sutton / Motorsport Images
F1 teams are currently only required to run tires at minimum tire pressure when they are first fitted to cars, as they are not required to maintain pressure once a car is on track.
That means the door is open for teams to find ways to reduce pressure after checks are done, but such a reduction in pressure means the tire is under more stress.
Pirelli revealed that new tire pressure and coverage protocols need to be put in place to ensure the Baku issue cannot happen again, as teams have already been briefed by the FIA on the new processes to follow.
The statement added: “Following this analysis, Pirelli submitted its report to the FIA and the teams. The FIA and Pirelli have agreed on a new set of protocols, including an improved technical guideline already circulated, to monitor running conditions during a race weekend and they will consider any other appropriate action. “
Red Bull has since responded to the findings and insists it ran its tires within Pirelli’s parameters.
“We have worked closely with Pirelli and the FIA during their investigation into Max’s tire failure on lap 47 of the Azerbaijani Grand Prix and can confirm that no car fault was found.” , indicates the Red Bull press release.
“We have adhered to Pirelli’s tire parameters at all times and will continue to follow their advice.
“We are grateful that after the high speed impacts over the weekend, no driver was injured.”