Pirelli says the tyre separation problem diagnosed after Friday’s practice in Qatar was so small that it was only visible under microscopic examination.
The potential safety issue compelled the FIA to take action ahead of Saturday’s sprint event to mitigate the risk of tyre failures.
The governing body established new rules on track limits fir Turn 12-13 and reserved the right to restrict tyre usage in Sunday’s Qatar Grand Prix by possibly mandating a three-stop race.
Pirelli's post-session analysis of tyres used in Friday's FP1 exposed a sidewall separation between the topping compound and the carcass cords on tyres that had been used for a long time.
The tyre manufacturer’s engineers suspected that the damage was caused by cars hitting the high pyramid kerbs under high G-loading at Turns 12/13/14 of the Lusail circuit.
However, Pirelli F1 boss Mario Isola said that the damage was so small that it was not noticeable to anyone prior to the tyres being cut open as part of Pirelli's standard analysis conducted after each day of running.
“If I cut the tyre and I show you the section, you cannot see any damage,” Isola explained. “It is so small, that obviously we can find the damage with a microscope.
“So, it's not an issue that we are saying, guys pay attention because we have a big issue now. It's an initiation, it's an indication, but obviously we cannot ignore it. That's why I reported what we found after our analysis [to the FIA].”
Ahead of this weekend’s round of racing at Lusail, the track underwent a complete resurfacing, while all the problematic kerbs from two years ago have been replaced.
But the new ‘pyramid’ kerbs that have been installed all around the track are hammering the tyres at a very high frequency according to Pirelli.
“The issue is – to give you an [explanation] that is not a lot technical but probably clearer – it is like if you take a hammer with a pyramid at the top, and you hit it against the sidewall for 100 times per second for a long period,” Isola explained.
“The compound is the weaker part. You have the chord of the carcass that is made with textile material and is a lot more resistant.
“So, it’s not a matter of fatigue. Fatigue is when you have the construction with fatigue [and] also the chord is affected.
“In this case, we don’t have an issue with the construction. It’s just the fact that you have a repeated impact on the sidewall that is affecting the resistance of the compound, localised where you have the chord.”
Pirelli is confident that there will be no tyre problems in Saturday's sprint race, which runs to 19 laps, as the issue has only affected tyres that have completed more than 20 laps.
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