(Motorsport-Total.com) – It has always been customary in the paddock that the notorious pessimists start predicting doom as early as Thursday of a race weekend – based on the weather forecast for Sunday. In Miami, this ritual now gains additional urgency. Not least because the race start was moved forward from 16:00 to 13:00 local time (19:00 CEST) to avoid impending thunderstorms.
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In fact, Formula 1 is currently not optimally prepared for wet conditions. The reason for this is the new tire dimensions this season as well as the limited comparative data from tests and races under identical conditions so far. Even the pre-Miami decision to raise the tire blanket temperatures for intermediates from 60 to 70 degrees Celsius is still experimental in nature.
First indications of the peculiarities of the new intermediates emerged during the shakedown week in January in Barcelona. On the second test day, conditions were wet, but only Red Bull and Ferrari each sent one car out on track.
Wet tires: What physically happens
The most important insight: The new intermediates apparently take longer to reach temperature and their full performance window. Although Pirelli still follows the philosophy of a coordinated tire family, construction and materials had to be adapted to the changed dimensions. The rim diameter remained unchanged, but the front tires were made 25 millimeters narrower, the rear tires 30 millimeters narrower. Additionally, both are built somewhat flatter.
The reduced contact patch and the lower air volume inside change the energy balance in the tire. Part of this energy is lost as heat when the rubber deforms under load. The assessment in the paddock is therefore that while Pirelli has successfully transferred the characteristics of the slicks to the new generation, the intermediates may have turned out somewhat too robust.
In addition, the wet tires still represent a work in progress. While they efficiently displace large amounts of water, they overheat quickly. In practice, this means: as soon as conditions become so bad that full wets would be sensible, a race interruption usually threatens anyway. Pirelli is working to make these tires more race-capable – but testing opportunities are rare and often politically sensitive, as teams are reluctant to accept rivals gaining extra track time with current cars.
Previous tests only conditionally meaningful
Since January, Pirelli has therefore been trying to accelerate understanding of the behavior of the intermediates. Most recently, in April, a Ferrari was used for two days on an artificially watered track in Fiorano. A test after the Japanese Grand Prix was also supposed to provide additional data – especially on dry tires. But rain thwarted this plan, at least providing opportunities for further use of intermediates and wet tires.
However, such tests only provide limited comparable data. Truly meaningful insights only arise when several teams drive simultaneously under representative conditions. Ideally in practice sessions of a Grand Prix weekend – or in the race itself.
“We started in Barcelona (at the shakedown in January; editor’s note) with Ferrari and Red Bull testing on the second day,” explains Pirelli chief engineer Simone Berra in Miami. “It was quite cold and there was a lot of standing water, and we collected the first feedback from them. It was a very early phase, and the teams, let’s say, started commenting that warming up under these conditions is a bit difficult, but of course only two teams, very cold conditions. Let’s wait for another significant test.”
“In Japan, we were unlucky in that it rained on both days and we had no opportunity to test the dry tires. But we had the chance to test intermediates and wet tires. With less standing water and somewhat higher temperature, the drivers’ feedback was still a kind of difficult warm-up, especially on the front axle, where it is complicated to keep the temperature in the working window.”
“So you start at 60 degrees (blanket temperature; editor’s note), and the risk is that if you don’t put enough energy into the tires, you continue to lose temperature. Then it becomes difficult to generate energy and increase temperature. So it’s a snowball effect.”
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“We started thinking a bit more about how we can support the drivers in this sense, so in agreement with the teams and the FIA, we decided to test at Fiorano with 70 degrees blanket temperature. There was a proposal for 80 degrees, but we wanted to take a first step, evaluate the first step, and then try to see where we stand, and then move forward.”
First practical test with 70 degrees
“At Fiorano (where the track was artificially watered; editor’s note), the test went well, but the conditions were slightly different because it was a bit warmer, significantly warmer. So after the test, after receiving the feedback that warming up was better and we were going in the right direction, it was decided to increase the blanket temperature from 60 to 70 degrees and wait for the first wet race to evaluate whether this step has a significant effect, there are no further warming problems, and overall we end up in a better situation.”
“That is now the next step for us because we also want to evaluate the intermediates with 70 degrees in the blankets with more teams. A test is a controlled situation, but we would like to see it at a race weekend, during a race, when you have eleven teams driving. Then you get more feedback and a clear overall picture of where we stand.”
From a purely data-analytical perspective, a wet race in Miami would therefore be quite welcome. Although the tires are homologated for the season, a better understanding of their performance in different conditions helps optimize deployment strategies – for example in setup, tire pressure, or temperature management.
The increase in blanket temperatures is intended to give the tires a kind of head start. During driving, energy is introduced into the tires when they deform in the contact area and then return to their original shape. Part of this energy is lost as heat.
Hot matter: How Formula 1 tires work
Formula 1 tires are designed to reach their performance maximum within a certain temperature window. For intermediates, this is about 80 to 100 degrees Celsius, for slicks between 90 and 110 degrees. Usually, the tires are preheated to 60 degrees before use, the rest is done by so-called hysteresis – i.e., energy input through movement.
However, previous experience shows that intermediates do not deform sufficiently under load to build up temperature quickly enough. Raising to 70 degrees is therefore an obvious step but must be validated under various conditions.
“Let’s assume it rains on Sunday, it’s a different situation anyway compared to all previous tests and considerations because the temperature is higher than what we had,” says Berra. “So let’s say it’s not really a final test. Let’s see how it goes this weekend, see how it goes if it rains, for example. In Montreal, it could be cold, it could be wet, and the energy of the track is not so high.”
“So we can still gather some information and then we can decide together with the teams where we move because obviously it is our intention to support them if there is something we can do in this sense.”
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