Pirelli’s preliminary investigation into the cause of the left-rear tyre failure that cost Max Verstappen victory in the Azerbaijan Grand Prix, and the similar problem that put Aston Martin driver Lance Stroll into the wall, excludes the possibility of either being caused by wear and points to debris as the suspected cause.
Verstappen was leading the race and completing his 34th lap on his set of hard tyres when the left rear let go and pitched him into the wall.
Stroll was running fourth and on the verge of pitting when he suffered his failure, having put 30 laps on the set of hards with which he started the race.
Pirelli has gathered remains of the tyres to conduct a thorough investigation, but the company’s Formula 1 boss Mario Isola has ruled out the possibility of a wear-related failure.
This is for several reasons, including the lack of warning before a sudden loss of pressure, the fact there was still adequate tread in the remains of both tyres, others running longer on sets of hards and that cuts were discovered in other tyres, including Lewis Hamilton’s rear-left from the second stint.
Isola said that the cut on Hamilton’s tyre “clearly came from debris” given its shape, but it was not deep enough to cause a loss of pressure.
“I believe I can exclude that the failures were due to tyre wear,” said Isola.
“We found a cut on the inside shoulder of a rear-left tyre used by Lewis Hamilton in the same stint. The cut is quite deep, probably 6-7cm, but did not cut the construction. So the tyre was still in one piece, it’s just the tread is cut.
“When there was the red flag and Lewis came to the pitlane and changed the set of tyres, we found the cut in the tyre. The rear-left tyre is not the most stressed tyre in Baku because talking about the rear tyres, it’s obviously the rear right.
“Another element is that there was no sign or anything warning according to the teams. We have to receive the telemetry from them but what they told us is that there was no warning, no vibration.
“These are the main elements collected in this short period of time.”
Isola also pointed to the fact that the right-side tyre is the more stressed of the rears at the Baku circuit, and the fact that others – including McLaren’s Lando Norris who ran 40 laps – completed longer stints on hards as supporting the belief the failures were down to debris.
A final report is expected before the French Grand Prix at Paul Ricard in two weeks, with the remains of the two tyres – as well as other tyres used by rivals during that stint of the race – being air freighted to the Pirelli lab in Milan overnight.
“It seems that it is a cut due to debris because it’s not the most stressed tyre,” said Isola.
“We have evidence of another cut in the same position, both of the accidents happened more or less in the same part of the circuits and a few laps difference, we have other cars with the same number of laps and the same tyres without any issues.
“So the preliminary investigation is that it is probably due to an external factor or debris or a kerb or whatever.
“Now the plan is to make a thorough investigation now and come back with a report to the FIA and the teams that hopefully will be before Paul Ricard. I will push to have a report as a priority.”
Isola also could not rule out the possibility of Verstappen’s failure being caused by debris from Stroll’s crash, which happened 16 laps earlier.
“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.
“I cannot exclude that there was something on track. In 2018, [Valtteri] Bottas picked up a big piece of debris on the main straight and he had a sudden deflation.
“In that case, it was visible from the images and we could see clearly what cut the tyre. In this case, it’s a bit more complicated. Another element of our investigation is if there are any images or footage that we can use to better understand what happened.”