Pirelli say debris likely cause of Stroll and Verstappen crashes, as they reveal cut found in Hamilton tyre

A pair of high-speed crashes for Aston Martin’s Lance Stroll and race leader Max Verstappen – from which both drivers emerged unharmed – turned the 2021 Azerbaijan Grand Prix on its head. But with both drivers appearing to have suffered left-rear blowouts, Pirelli boss Mario Isola told media after the race that he believed debris on track at Baku was the cause.

On Lap 30 of the race, Stroll had just passed the site of his Q1 crash from Saturday when he appeared to suffer a blowout near the pit entry and spun violently into the wall, bringing out a Safety Car.

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Following the subsequent race restart, Verstappen was then leading with five laps to go when he suffered his own blowout going down the main straight, the Dutchman also spearing into the wall after his left-rear tyre appeared to let go.

But Pirelli’s Head of F1 and Car Racing didn’t believe that tyre wear had been the issue in either incident, with Mario Isola telling the media: “I believe I can exclude that failures were due to tyre wear, because it's not a matter of tyre wear…. The rear-left tyre is not the most stressed tyre in Baku because... it's obviously the rear-right.

“I don't want to give any preliminary conclusions. But it seems that it is a cut due to debris, because as I said, it's not the most stressed tyre… We had other cars with the same number of laps [on the] same tyres without any issue. So the preliminary investigation is that it is probably due to an external factor, or debris, or kerb or whatever.

“Another element was there was no sign, or any warning according to the teams,” Isola added. “We have to receive the telemetry from them but what they told us was that there was no warning, no vibration nothing to seem that there would be something [wrong] in the tyres.”

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Isola suggested that Verstappen’s crash could have been caused by running over debris from Stroll’s crash, likening the incident to Valtteri Bottas’ tyre failure after running over debris while leading the 2018 Azerbaijan Grand Prix.

“For Max, it could be debris from Lance's car,” said Isola. “For Lance, honestly I don't know because there were no incidents before his crash, so I cannot exclude that there was a part of something on track.

“In 2018 if you remember, Bottas picked up a big piece of debris on the main straight and he had the same problem with the sudden deflation. In that case, it was visible from the images, and we could see clearly the piece of debris that was cutting the tyre. In this case, it's a bit more complicated.

“Obviously another element of our investigation are images and if there is any camera, any image, any video, any footage that we can use to better understand what happened [we’ll use it].”

READ MORE: Hamilton explains switch issue that led to him dropping from P2 to P15 at crucial Azerbaijan GP restart

Meanwhile, Pirelli announced that they’d also spotted a cut in the hard tyre of Mercedes’ Lewis Hamilton, discovered when he pitted under the red flag caused by Verstappen’s crash.

“We found a cut on the inside shoulder on the rear-left tyre used by Lewis Hamilton in the same stint [as Verstappen],” said Isola. “The cut was quite deep and big, probably 6-7cm, but not cutting the construction, so the tyre was still in one piece, just with this cut. And when there was the red flag and Lewis and came to the pit lane and changed the set of tyres, we were able to find the cut in the tyre.”

Pirelli will now air freight the tyres back to their Milan laboratories in order to perform a full investigation, with Isola adding that he would push to have a report for the teams in time for the French Grand Prix in two weeks’ time.