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Insight: What is it about Pirelli rain tyres that means wet F1 races need careful management?

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Insight: What is it about Pirelli rain tyres that means wet F1 races need careful management?
Nov 17, 2016, 2:25 PM

Two red flags and 27 laps driving behind the Safety Car at Interlagos on Sunday, but we had F1 drivers saying that the conditions were nothing like...

Two red flags and 27 laps driving behind the Safety Car at Interlagos on Sunday, but we had F1 drivers saying that the conditions were nothing like as bad as Silverstone in 2008, for example.

So what was going on in Sunday's Brazilian Grand Prix that made the Race Control take a cautious approach, even red flagging the event the second time without an accident to trigger it?

Many fans have been asking this question.

Pirelli wet F1 tyres

Nico Rosberg offered the beginnings of an answer after the race,

"It’s down to the tyres, you know, not coping well with the aquaplaning. We know that and we’ve been working on that now for next year and so we’re hopeful to make progress on that. Of course it would be good, you know, if it wasn’t so on the edge as soon as there’s a bit of standing water."

Max Verstappen added another important detail: "It’s a combination of having more horsepower now (compared to ten years ago), so more torque, so the cars are speeding up more and less downforce at the moment. Yeah, I think next year it should be solved already, it will be much easier to drive the cars in the wet because of having quite a lot more downforce on the race. Of course, I think we can do improvements on the tyres, we’re working on that for next year but I think that with more downforce that should help already."

Fuji F1 2007

But there is more than meets the eye on the question - why are the Pirelli wet tyres seemingly not on the level of the Michelin and Bridgestone wet tyres of the past?

To fully understand this we need to go back to the mid 2000s, when there was a tyre war between the two tyre giants. At that time they each had partnerships with their contracted teams and they tested extensively with them. Ferrari was Bridgestone's main team, while Michelin had a close relationship with Renault in particular, but also with Williams and McLaren.

Because of the tyre war, the manufacturers did extensive testing of all types of tyres, including intermediates and wets. With slick tyres the main areas to concentrate on are compounds and construction, while with wet tyres you add in the tread pattern.

Renault F1 2007

Engineers working on the Michelin programme have told this website that in a typical day's wet weather tyre testing, they would try 18-20 sets of varying stiffness, tread pattern and compounding in a process of elimination that arrived at the right tyre for F1 wet races.

Pirelli has neither the access to the test days or the cars to do that level of work and possibly for that reason, hasn't signed up many of the engineers from Michelin or Bridgestone from that era.

As testing is limited and wet races feature relatively rarely in the F1 calendar, the bulk of the work goes into the five different slick tyre products. The 2016 rules say that teams must select three different compounds and by and large this has worked pretty well this year with some interesting strategy choices.

In winter testing this year there was a limited amount of wet tyre testing and results were not ideal especially with regard to the base of the channel of the grooves and its ability to move large amounts of water. With precious little time to work on it, as Pirelli could only work with the limited test days allowed in the rules and with no specific team affiliations, there was not much more to be done.

Max Verstappen Daniel Ricciardo

But on a day like Sunday where you have proper rain and a fully wet condition, the critical point where the wet tyre cannot shift the water can arise and that has just been something everyone on the inside of F1 was aware of and would have to manage if and when it arose, as it did on Sunday.

The second Red Flag came about because of this - not for an accident - and drivers were frustrated because in the initial laps as they circulated, they felt that it was ok to race and was at an intermediate condition, but moving slowly behind the Safety Car the water was allowed to build up on the track surface and the tyre temperatures fell and that brought out the second red.

Mark Webber Tweeted at the time that the Safety Car should be ditched and the leader, Hamilton, should lead the cars around at 60% pace until a consensus of drivers said that it was good to race. This is how it is managed in karting and all the F1 drivers have experience of this kind of situation, so would have no problem adapting. Some will be calling at the next Drivers' Meeting for this to be adopted in future in F1.

"I don’t really understand why the last one (red flag) came out but the track was the same pretty much throughout, apart from after the first Safety Car so it was kind-of a pointless need to have a Safety Car come out, we should have just kept going," said Hamilton.

There is also the unspoken aspect of race manageent post the Jules Bianchi accident in Suzuka 2014, which comes into play at times like this and adds an extra layer of sensitivity.

There has been a strong emphasis on wet weather tyre testing for the new F1 2017 rules, partly because of the above but also as there was concern that a wider tyre might lead to greater risk of aquaplaning. Red Bull has done two tests in the last two weeks on a wet track in Abu Dhabi Pirelli's Mario Isola reported last weekend that this had made good progress for next year. The wet tyre specifications are now set and will go into production.

In the two pre-season tests for all teams at Barcelona, if it has not rained by Day 3 of the first test, then the fourth and final day will be a wet tyre test for all F1 teams.

It is worth pointing out that another dynamic at play here is that F1 teams now have such sophisticated simulators that they don't need to test as much as 10 years ago. They can carry out development work, aerodynamic simulations, and much more without leaving the comfort of their team headquarters; hence the way the testing has been cut down so dramatically in recent years.

This saves money, travel costs, mechanics' time and much more. But it doesn't help Pirelli, which needs cars on a track to develop its products.

Another example of where the business side of F1 acts to the detriment of the sporting side? As ever it's a bit more complex than that.

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