Pirelli reveals cause of tyre failures in Azerbaijan GP

Pirelli's investigation into the tyre failures suffered in Baku by Aston Martin's Lance Stroll and Red Bull's Max Verstappen concluded that there was no production or quality defect on the tyres.

Both Stroll and Verstappen suffered left-rear blowouts, with the Canadian's failure occurring after 30 laps while the Dutchman's rupture took place just five laps from the checkered while the Red Bull driver was comfortably leading the race.

A post-race examination of Lewis Hamilton's tyres revealed a deep cut in the left-rear rubber which led to speculation that the failures had perhaps been caused by debris.

But Pirelli's investigation has ruled out that theory.

"Pirelli, in conjunction with the FIA, has completed the analysis of the left-rear tyres involved in the incidents that affected Lance Stroll and Max Verstappen during the recent Azerbaijan Grand Prix," said Pirelli in a statement released on Tuesday evening.

"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.

"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."

In the aftermath of the Baku crashed, both Red Bull and Aston Martin stated that they ran their tyres to the minimum pressures mandated by Pirelli, a fact that Red Bull repeated on Tuesday.

"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," said Red Bull.

"We adhered to Pirelli’s tyre parameters at all times and will continue to follow their guidance."

Nevertheless, in agreement with the FIA, Pirelli will rely on new pressure and tyre blanket protocols from this week's French Grand Prix while a new technical directive issued to teams by the governing body should discourage the former from tampering with pressures.

As a reminder, while pressures are checked when a tyre is fitted, Pirelli has no way of monitoring pressure levels when cars are in action on the track.

"As a result of this analysis, Pirelli have submitted their report to the FIA and the Teams," said F1's tyre supplier. Teams are therefore entirely responsible for keeping pressures within the limits  set by Pirelli.

"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."

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