Pirelli F1 Racing boss Mario Isola has confirmed that Red Bull’s and Aston Marin’s Baku F1 tyre failure was “a circumferential break on the inner sidewall, which can be related to the running conditions of the tyre”.

Championship leader Max Verstappen and Aston Martin’s Lance Stroll both were force-out following left-rear tyre punctures in Baku which has triggered new tyre rules for this weekend’s French Grand Prix and for the rest of the season.

“At the beginning [of our investigation] the idea was there was some debris cutting the construction, because obviously we had the evidence of other tyres with some cuts on the tread. But then when we finalised the investigation, we found that… the failure was not related to the cuts that we found not only on Lewis [Hamilton’s] tyre, but also on one tyre from Sebastian [Vettel]. Those cuts were due to debris for sure, but the debris was not sharp enough to cut the construction. Isola told Formula1.com

“What happened in Baku is simply that the running conditions expected [i.e. the conditions when the cars were moving] were different compared to the actual running conditions, and that created the failures. The failures were a circumferential cut on the inside shoulder.

“When you have a lot of energy going through the tyres, with the pressure that is lower compared to the expectation, the result is that on the side wall, you have what we call standing waves and standing waves are putting a lot of energy into the shoulder of the tyre and at a certain point the tyre failed, and that is what happened and the reason why we had this situation in Baku. said Isola.

“In this case, we didn’t achieve the 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 compared to what we were expecting. [But] we didn’t say [in Tuesday’s press release] that the teams did something that is not permitted in the regulations.”