Pirelli increase tyre pressures for French GP and specify new “cooling curves”

2021 French Grand Prix

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Pirelli has increased the minimum starting tyre pressures for the French Grand Prix and detailed several new restrictions in line with updated rules which come into force this weekend.

The changes follow the failures Max Verstappen and Lance Stroll experienced during the Azerbaijan Grand Prix two weeks ago. Pirelli confirmed these occured because their tyres were running at lower pressures than was expected based on the starting tyre pressures which were set for the event.

From this weekend Formula 1 teams will be subjected to new tyre checks conducted when the rubber has cooled, and also once it has been re-heated. Pirelli has issued a “cold pressure cooling curve” for the first time, which indicates what minimum pressures each tyre should achieve at a range of temperatures.

The minimum starting pressure for rear tyres for the race has been adjusted. On Monday Pirelli specified a minimum of 19.5psi for this race, which has been raised to 21.5psi. The minimum pressure for front tyres remains at 21psi.

The minimum re-heat pressure for slick tyres – which has been set for the first time this weekend – is 0.5psi lower than the starting pressure for both axles. The expected stabilised running pressures are no less than 22psi for the fronts and 22.5psi for the rears.

The tyres drivers use to set their quickest lap time in the final stage of qualifying they reach, and all sets used in the race, will be selected for cold pressure checks and potentially re-heat pressure checks.

Following Friday practice at the Azerbaijan Grand Prix, Pirelli increased the minimum front tyre starting pressures but left the rears unchanged. Verstappen and Stroll both suffered rear tyre failures during the race.

Pirelli’s head of motorsport Mario Isola said that, in retrospect, the rear tyre pressures should have been increased by “probably another couple of psi, 1.5 or something in the range of that.”

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Keith Collantine
Lifelong motor sport fan Keith set up RaceFans in 2005 - when it was originally called F1 Fanatic. Having previously worked as a motoring...

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36 comments on “Pirelli increase tyre pressures for French GP and specify new “cooling curves””

  1. When you need to implement complex regulations & guidelines like this just to stop tyres failing then something isn’t right.

    Pirelli need to go because this is a joke.

    1. When you’ve got cars with enough downforce to drive upside-down and couple them with teams that have hundred-million dollar budgets and the best engineers in the world whose only job is to come up with ways of obeying the letter of the rules while contravening their spirit, then yes, complex regulations is what you need.

      1. @aesto So other (Far better) tire suppliers from the past managed to not need this over-regulation how?

        The cars are constantly developing, evolving & improving. That is what the sport is, Always has been & it was always the case that the tire suppliers had to develop the tires to suit that development. Never in F1’s history has the sport ever needed to introduce absurd over-regulation to hide the deficiencies of the product its incompetent tire supplier was giving it.

        And these awful Pirelli joke tires were still suffering many of these problems & still required to be babied like no tires have done in F1’s history back when the cars had less downforce, were slower & lighter.

        Indycar don’t have any problems as they are heavier than F1 cars & put far more stress on the tires on the ovals for more extended periods of time than tires in F1 will ever see because Bridgestone is a competent tire supplier capable of producing tires that suit the sport they supply tires to. Pirelli are not competent & are incapable of supplying F1 quality tires.

        They are a joke, There tires are a joke & its about time after a decade of failure that they step aside & let somebody else have a go.

        1. The excuses from Pirelli & there blind defenders needs to stop, It’s been a decade now, A decade of repeated & constant failure & incompetence.

          The pinnacle of the sport should not be stuck with the worst tires in all of motorsport.

        2. It never stops, does it?

          I’ll repeat myself here yet again – no tyre manufacturer (ever) has had to come up with something that is put under the same conditions as the current F1 tyres are under. Teams have never had so much knowledge on the tyres and so many tools at their disposal to exploit every last bit of performance from them for so long.

          I know you think that Pirelli are rubbish and that Michelin or anyone else could do better, but there’s simply no evidence to support your opinion.
          Comparing current F1 with that from 15+ years ago is like comparing the same with road cars – everything has changed in that time. Not least of which now is that F1’s tyre supplier (whoever it may be) is under extremely strict conditions in regard to what tyre characteristics they need to aim for and the amount of development they can do themselves.
          Personally, I see nothing wrong with the teams being in the position of needing to make choices about how much performance they extract from a tyre, and how much stress they put it under.
          In some ways, there is nothing at all wrong with Pirelli’s tyres – the bulk of the problem is the cars they are bolted on to.

    2. Workaround after workaround.

  2. Black and white now that it was a tyre failure in both cars in Baku. Be it caused by low pressures or not, it was structural. Verstappen and Stroll are right to complain about the “what ifs…” No debris, drainage cover or kerbs to blame, nor Hamilton’s tyre cut was a clue to anything.

    But now comes the hard part: who will benefit (or loose) from the higher pressure? It adds a random effect throughout the field and can change the balance in such a close fight. Midfield specially, but also between the title runners.

    Who is going to figure out first which setup changes are needed? Expect some (maybe unfair) surprises…

    1. I’m expecting a solid race from McLaren.

    2. No, they were not right to complain, as their teams put them at risk by gaming the rules to run at a lower than recommended tyre pressure.The fact that they passed scrutinising doesn’t change that.
      At 300kph, the tyres rotate somwhere around 40x per second, which means as the sidewall deforms, any spot on the shoulder of the tyre is flexing eighty times per second. That’s a lot of energy going into the shoulder of the tyre.
      Lower pressures mean greater flex, and greater energy, and that is why the Red Bull and Aston Martin tyres failed.

      1. Guess what… you missed the point. Scrutinising confirmed that it was not the teams that put the drivers at risk. Because the teams did not run at a lower than recommended tyre pressure. The tyres failed because they had a lower than expected tyre pressure during the race. A wrong expectation from Pirelli by how much the tyre pressure would/should have gone up during racing.

        Reply moderated
      2. Flex is just a margin just use a ballon for example you blow it normal you manhandle it (without nails) it should survive now blow it up above that do it again it will fail.
        If you fill it for less and manhandle it it never fails. So if they used it as specified the ballon put a weight on it (downforce) manhandle it( flex) it will fail then you can say the ballon is here the failure.

        So it’s clearly Pirelli’s fault.

        1. Tyres aren’t made like balloons, @macleod. Not even close.
          Try attaching balloons to your car and driving around on them for a while and see how long they last.

  3. So why is it not enough to deal with the tricks used by the two teams that were running under pressure and both suffered tyre incidents?

    The teams that were on the “expected” pressure didn’t have an issue.

    1. @f1osaurus Pirelli haven’t confirmed that the other teams were on the “expected” pressures. After all they found a cut in Hamilton’s tire during the red flag period as well.

      1. @randommallard They found a cut and they that’s determined that was not the issue.

        1. @f1oSaurus They said on that Sunday that the signs were initially pointing to cuts on Verstappen and Stroll’s tires as well. A cut doesn’t have to mean only one caused by debris or a kerb.

          1. @randommallard Yes and they changed their mind and said the cuts were not the root cause, but instead low running pressures were.

          2. @f1osaurus Low running pressures were indeed the cause. I cannot argue with that. But I am yet to see any proof that these 2 teams were running pressures that were *too* low. They were meeting the minimum pressures at the times the readings were taken, as stipulated by the regulations. Pirelli can suspect otherwise, but if they cannot prove it then it can’t be taken any further. And the lack of outcry from the other team principles suggests that these two were not the only teams employing any potential, but I stress unconfirmed, trickery.

          3. Ok I’ve only just seen the quote from Seidl asking for more clarification. But like Ferrari’s engine, it appears to be a case of something being legal because it was not specifically outlawed.

            To quote the article on this site about Pirelli’s report:

            Formula 1’s official tyre supplier determined both that its product performed as intended and that teams followed the prescriptions on using them.

          4. @randommallard They can request the pressure data from the teams.

            Mercedes, Alpine and McLaren have already cried out. So you are just arguing semantics really.

          5. @f1osaurus I have seen McLaren ask for clarification, but have not heard much out of Mercedes beyond Hamilton playing mind games, and have heard nothing out of Alpine. If you could point me in the direction of those articles I would be grateful.

          6. @f1osaurus Thank you. I had not previously seen that interview. However there are a couple of things in there that are important. First of all the headline says ‘I’m, and later in the article it says:

            Budkowski would not go as far as to say that tyre pressure tinkering has definitely occurred

            This is important. There is no firm evidence that tinkering took place. We only have the word of a tire supplier that probably wants to get people off their own back so tries to shift the blame elsewhere (see the Chapel kerb at Silverstone for example). Even then, they haven’t provided any evidence such as data or testimony. There is nothing to prove that Red Bull or Aston Martin did anything wrong, and the FIA need to act on an innocent until proven guilty basis, not guilty until proven innocent. If there later emerges evidence that either or both teams were in the wrong, then I’ll hold my hands up and admit I was wrong.

            (I’ll also note that on another thread you told me not to believe everything that comes out of the mouths of Team Principals, so I’ll take that in mind with Budkowski as well)

    2. @f1osaurus We only have Pirelli saying that AM and RBR were running tyres with low pressure, but, there is no evidence to prove that they were. All we have once again is Pirelli deflecting blame for defective tyres.

    3. When you have to increase your tyre pressure by a full 2 psi sorry you can’t put the blame on the teams anymore.
      That is a massive difference on a track that is slower then baku.

      1. Well that’s exactly my point. They set the required starting pressure in an attempt to arrive at the desired running pressure. And that was too low only for a few teams. So now they make everyone run at higher pressure.

        1. So if you start with the prescription pressure and as a result of good design your tires do not overheat and as a result not increase in pressure. Then according to your dimension the team is at fault.
          You know Mercedes did abused the tire pressure in 2015. But probably not, knowing your selective memory.

          1. So if you start with the prescription pressure and as a result of tricks to circumvent the tests and to lower the temperature. Then when you are running at a pressure clearly visible from the tyre pressure monitors to be below the advised minimum. Then according to your dimension, the team is totally not at fault?

            They willingly did this. Stop lapping up the lies damn Verstappen hooligan!

            It’s disgusting that the FIA need to change these tests and spend more resources to actually warm them back up to running temperatures to check if Red Bull wasn’t cheating again.

            Mercedes did nothing wrong with the tyre pressures. A cold tyre from a parked car gives a different pressure. Yeah so what. Seriously. Stop pretending you are clever with this dumb nonsense.

          2. Oh snap, there’s a beef here!

  4. Next we will hear yelling from Mercedes about balloon pressure when they failed to win

    1. Nope, they already pointed the silver arrow at the pitstops by red Bull.

  5. I think the relative silence of Christian Horner and Lawrence Stroll says it all.

    1. They would have started a 24h press conference against Pirelli. Everything less than that raises doubts about the real pressure of their tyres…

    2. @schivo69 I think the relative silence of all the team principals bar Seidl says it all

    3. @schivo69 Exactly. The only thing we hear/read is other teams state that circumventing the safety guidelines is a serious issue.

      Alpine and McLaren team bosses have already said that they want more clarity on what actually happened, but instead FIA/FOM decides to cover it all up like they did with the secret agreement they had with Ferrari.

      Personally I think this Baku tyre pressure case is worse because playing loose on safety guidelines could result in serious injuries and/or damage to other teams.

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