Pirelli has finally offered a full explanation for what caused two scary tyre failures during the Azerbaijan Grand Prix.
Both Lance Stroll and then-race leader Max Verstappen both suffered left-rear punctures at well over 300kph on the long main straight at Baku City Circuit.
In their initial report, the Italian supplier absolved themselves of any blame, insisting the production and quality of the tyres met the standard and there was not any fatigue or delamination.
Instead, Pirelli said a failure of the inner sidewall of the tyres was due to the "running conditions", in other words how they had been used by the teams.
Both Aston Martin and Red Bull quickly denied any wrongdoing, insisting they were operating the tyres within the guidelines set, but now Pirelli has gone into more detail about what occurred.
“What happened in Baku is simply that the running conditions expected were different compared to the actual running conditions – and that created the failure,” motorsport boss Mario Isola told reporters in France.
“When we prepare the prescriptions [for minimum pressure], we receive simulations [from the teams] and we consider margins.
“The expected loads, the downforce or the speed, are simulated, so it is not exactly the value that we find on track. And in this case in Baku, we also found some parameters that were not exactly what we found on track.
“We assume that they are running at a certain pressure, and a certain camber. And with a margin on it, of course, we run in a condition that is okay for the tyre.
“In that case, we didn’t achieve these conditions, not because teams were doing something against the regulations, but because they were looking as usual for performance, and that created a different scenario to what we were expecting.
“And the different scenario was that mainly the tyres were running at a lower pressure compared to the expectation.
“Then, when you have a lot of energy going into the tyres with a pressure that is lower compared to the expectation, the result is that on the sidewall you have what we call standing waves.
“Standing waves are putting a lot of energy into the inside shoulder of the tyre and at a certain point, the tyre breaks. That is what happened, and the reason why we had this situation in Baku.”
The safety of Pirelli's tyres certainly isn't a new topic, dating back to when six failures took place during the 2013 British Grand Prix alone and multiple others since.
At Circuit Paul Ricard, drivers opted not to attend a proposed meeting with Pirelli to discuss what happened in Baku and now some are admitting concerns not just with their product, but also their transparency.
“Personally not, because for me it was just a bit vague, what came out,” Verstappen, who was very critical after his crash, said when asked if he was satisfied with the supplier's conclusions.
“The only thing I can say is from our side the team did everything like they should have done, I mean they followed all the guidelines with tyre pressures and stuff, so there was nothing to be found there.
“It would also be nice to just know if it was tyre pressure-related… just speak out, I think that would be I think a bit easier to understand than I think the explanation we got so far because the team didn’t do anything wrong.
“They explained that they don’t have measurement tools during the race but we gave them our tyre pressures and they were within the limits they set.
“If those limits are not correct, there is nothing we can do about it, we just follow what is possible within the rules. If that means we have to go up on pressures we will, everyone will go up on pressures.
“They have to look at themselves and we are here, of course, happy to help with everything but they already went up on pressures from Friday to Saturday so that means that something, maybe it wasn’t enough.
“We will go up on pressures and hopefully that is enough.”
Sebastian Vettel has also suffered a few tyre failures during the Pirelli era, and was asked if he had trust in their product.
“I think the short answer would be, I can’t say 100% yes, and I can’t say 100% no,” he said on Thursday. "I don’t think I need to add a lot.
"The demands are very high and it’s not always easy to get everything right. So, if you’re trying for the perfect product, to make everybody involved happy, probably it’s not going to happen.
“I think I’ll leave it there. I’ve said enough.”
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However, one voice defending Pirelli was Lewis Hamilton, who does believe Red Bull and Aston Martin likely caused their own problem.
“As you know every weekend, whenever there is a failure, they always put the pressures up – so that tells you something,” he said.
“More often than not, [it’s] that the tyres are not being run at the pressures that are being asked. We didn’t have a problem with our tyres.
“I think they’ve done a great job with the tyres this year, they’re more robust than before, and I think in this particular instance, I don’t think Pirelli are at fault.”
In the wake of Baku, the FIA is set to monitor tyre pressures more closely with random checks after they have been used on track.
Also, how teams use tyre blankets will be more closely observed to limit any possible tricks.
“At the end of the day, safety is always the priority, and for me and for my team, there have been clear rules and guidelines as to where we have to operate,” Hamilton continued.
“So I was very surprised naturally to see that they [the FIA] had to clarify those, which obviously, you can take what you want from that.
“I’m happy that they have acknowledged that they need to clarify it, and I think what’s really, really important from now is how they police it because they’ve not been policing how the tyres are being used, tyre pressures, tyre temperatures, and we need to do better.
“It’s great that they’ve done a TD (technical directive), but it’s the action now. We need to see them really follow through and be really vigilant to make sure that it’s equal across the field.”
