The freshly water-blasted track surface at Istanbul Park continues to give Pirelli something of a headache this weekend, as their analysis of the wet weather running on Saturday has yielded different tyre performances compared to initial expectations.
On Friday, Pirelli's Mario Isola explained that the dry compounds used this weekend may be a step too soft for the freshly-treated Istanbul Park track surface. The surface went through a water-blasting treatement to improve the grip after being more like an ice rink in 2020, but word of the process reached Pirelli too late for them to alter their tyre compound choices.
With rain falling on Saturday during practice, Pirelli also found that the increased grip even affected how the cars responded to the track surface when on the Intermediate or Wet tyre. As a result, the crossover point between the tyres is much different to originally anticipated – something which could have a huge effect on the race if inclement weather does hit.
"The comments on both Extreme Wet and Intermediate were positive," Isola told RacingNews365.com on Sunday morning.
"[The] Wets were working well on the three or four cars that did a few laps. They didn't report any warm up issue, any grip issue, so they were working well.
"The Intermediate was used more extensively during the session. The only observation I can make is the crossover time. That is very different compared to our expectation."
Explaining the crossover points between the compounds, Isola said it's done through a percentage calculation as opposed to the lap time itself.
"Usually we use a percentage from the time in dry condition," he commented.
"Basically, if you have 1:24 for dry, you consider 112 percent more for the Intermediate, 118 percent for the cross between slicks and the Wet. If you make it a calculation, it is 1:34 for the Intermediate, 1:39 for the Wet. You use the percentage, not the absolute time, so it's working quite well.
"Yesterday during FP3, we realised that the crossover between Wet and Intermediate was 1:36, so three seconds faster than the expectation, and between the Intermediate and slicks was 1:30/1:29, so four to five seconds faster."
There is a chance of rain during Sunday afternoon's race, although the official forecasts still suggest a 20 percent chance or less. But according to Isola, rain could have a major bearing on the Grand Prix, and this crossover information could prove vital.
"They [the teams] have to consider that for the strategy in changing conditions because, yesterday, when the track was 1:33/1:34, it was still not ready for slicks," he said.
"The expectation was for 20 percent of rain this afternoon, 60 percent this morning at nine o'clock. Honestly, it looks a bit worse than the expectation.
"The other point is that we saw how difficult is for the track to dry. The water is staying there and you have many, many places where the standing water is there, so it's difficult."
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