The "curveball" offered by F1's mid-season change of Pirelli tyres

Tyres have played a critical role during 2021, not least in the delicate competitive balance between Mercedes and Red Bull. Thus a change for the 10th race of the season that potentially makes a lot of valuable knowledge obsolete is not a small matter.

As of now nobody, including Pirelli and the teams, knows how the change will play out. The new tyres have not been run on track, and won't be until they are tested on Friday at next week's Austrian GP.

The move to a stiffer rear sidewall could make little or no difference, or it could have an impact on the balance of competitiveness up and down the field, at least until teams learn how to manage them.

To add to the intrigue they will be introduced at F1's first ever sprint qualifying event at Silverstone, when all teams are taking a step into the unknown in terms of how they run their weekends.

They will use the new tyres in FP1 on Friday morning, and then go straight into qualifying and parc ferme conditions in the afternoon, with very little opportunity to adjust their cars.

"That's a curveball," said Mercedes boss Toto Wolff when asked by about the impact of the new tyres by Motorsport.com. "Nobody really knows on which head it is going to detonate. You could be on the lucky side or on the unlucky side. We're going to test them next week and see what they do. But it's very much an unknown.

"It affects a lot, because we only have this 60 minute session now, so we are time-limited anyway, and now you need to test another tyre. But as long as it's the same for everybody, we can cope. We will take on the challenge and try to find out what to learn from these tyres, and what feedback to give Pirelli, and that's fine."

The new tyre is part of Pirelli's response to the failures experienced by Max Verstappen and Lance Stroll in Azerbaijan. The first step was the technical directive that clamped down on tyre operation for the French GP, along with higher rear pressures.

Max Verstappen, Red Bull Racing RB16B looking at the tyre after retiring from the race

Photo by: Mark Sutton / Motorsport Images

Heading to Silverstone, a venue notorious for ultra high loads and tyre issues, Pirelli wanted to take another step.

The possibility of changing rear construction has been discussed over the past couple of weeks, and the plan was confirmed in a gathering of team bosses in Austria on Friday afternoon, chaired by F1 boss Ross Brawn. Pirelli's Mario Isola was given the opportunity to state the Italian company's case.

Brawn's presence as the chair of the meeting indicated what a big change this is, and how important it is to avoid a repeat of the Baku failures. However he downplays its potential impact.

"It's an evolution," he told Motorsport.com after the meeting. "Pirelli want to give some more margins for the teams to work with. And it's a sensible change. I think it's something all the teams support, and a logical move.

"I think the changes that were done with the pressure control would have handled the situation. But we want to give ourselves a bit more margin."

But could the change lead to complaints from teams that initially struggle to adapt to the new tyre?

"Well, F1 is very competitive, so someone will find an issue! But I don't think so. I think the teams are very supportive, and I'm optimistic there'll be no issues."

Teams have only been given some basic information about the tyres, and they will receive more comprehensive details on Tuesday. Then next Friday each driver will have two sets to run in either FP1 or FP2, on top of the regular race weekend allocation. That test is essential, and without a positive outcome, the new tyres cannot be raced at Silverstone.

"We are talking about the construction that we never tested before on track," said Isola. "That construction was an idea that we had last year, when we were developing the 13-inch tyres for 2021. If you remember, we tested different constructions in Portimao. And then we had a deadline to respect to homologate the new 2021 construction.

"But after Portimao we had also some other ideas on how to make the rear tyre more robust. And we made some prototypes. We usually run several indoor tests to assess the level of integrity of the tyre. And the new construction was positive in this regard.

Pirelli tyres

Photo by: Steven Tee / Motorsport Images

"The 2021 construction is for sure a step better than 2020. But the new one we want to propose is another clear step in the direction of having a tyre that is more robust than the current one.

"Why do we believe we want to test it and why we want to introduce it? It is true that with the new technical directive we have a much better situation now. The type of controls and number of controls made by the FIA are giving us a good guarantee about the way in which teams are running the tyres.

"But it's also clear that we don't yet have a standard [pressure] sensor. And until 2022 it's impossible to introduce a standard sensor. So the situation has improved massively compared to a few races ago, but we still have this impossibility to check the running pressure. And we have a busy year in front of us. So we believe that having this solution in the pocket, and not using it, is not the right decision."

The new tyre also allows Pirelli to try some ideas for next year, as Isola explained: "This new construction has some concepts that we are planning to introduce also in the 18-inch tyre.

"So when we found that this improved integrity on the prototype, we tested end of last year, those concepts were taken for the 18-inch tyre. And now, if we introduce it, also on 13 inch. It's a good test also for the 18-inch tyre, because the idea behind is on both tyres."

Like Brawn Isola downplays the potential impact on teams, stressing that the profile of the new tyre is the same as the current one.

"I'm not expecting a different driveability," he said. "Obviously, it is a different construction in terms of geometry and design of the tyre. We are not going to change the external profile, because otherwise this affects the design of the floor and the downforce on the rear of the car.

"So it is not going to change these elements. But it is more robust. In terms of driveability, I'm not expecting a big shift in balance, or something like that. But we need to test it on track to confirm that."

Despite what Isola says about the unchanged static shape of the tyre, at speed a stiffer sidewall will flex in a different way. That dynamic change will inevitably have an aerodynamic impact, particularly with regard to the interaction between the tyre and the floor – a critical area for all 2021 cars.

There's also something else to consider within the cars too - the overall vehicle dynamics aspect. Tyres are considered a part of the car's suspension, as they provide a given additional spring rate within the system. With a stiffer sidewall, this would introduce a greater spring rate, and also affect other dynamic parameters such as cornering force and slip. However, if Pirelli has offset that with the rest of the construction, then it could be that the lateral forces put through the tyre are about even.

Lance Stroll, Aston Martin AMR21, Daniel Ricciardo, McLaren MCL35M, Sebastian Vettel, Aston Martin AMR21, Charles Leclerc, Ferrari SF21, and Mick Schumacher, Haas VF-21, as drivers practice their start procedures

Photo by: Glenn Dunbar / Motorsport Images

Asked if the status quo could be impacted, Isola added: "On paper, the changes are not big in terms of expected behaviour. And so I don't think that they will affect the competitive order of the teams.

"They have to test them and obviously they will try to understand the new tyre as soon as possible. That is normal, there is always a learning curve.

"Obviously, we are not talking about a completely different tyre. That means I'm not expecting that this learning curve will be a long period."

The teams have had no say on the decision to proceed with the new tyre, but Isola also explained that they've accepted it as a move that will improve safety.

One intriguing aspect of the change is that it should allow Pirelli to drop back down on rear pressures, which were hiked for France and the Austrian races.

"The new construction is designed to work at a lower pressure compared to the current one," Isola noted. "Being more robust, you can run it at a lower pressure. And then the pressure obviously is always defined on the simulations we receive, and also considerations on the level of running pressure at which they stabilise."

Pirelli has already made enough new tyres for Silverstone, and in case they can't be used – for example because next Friday in Austria is rained out and teams are not asked or do not agree to try the tyres in FP3 – there is also enough stock of the current tyre available.

Isola insists that despite last year's issues Pirelli doesn't have concerns about going to Silverstone with the existing tyre, should that ultimately be necessary: "No, because we have changed the construction this year. The front is different not only in the construction, also the profile on the front, we had the possibility to make a further step on the new 2021 construction, changing also the profile, a step that was not possible on the rear.

"But with the new conditions we are not worried about the integrity of the current tyre. If we want to introduce the new one, it's because it's available, and because we believe that we have more margin, not because I'm worried about anything."

Pirelli tyres

Photo by: Steve Etherington / Motorsport Images

So what do the teams think? As it's a safety issue, they have been happy to back Pirelli and the FIA.

"In the end the most important thing is safety," McLaren boss Andreas Seidl told Motorsport.com. "And, therefore, we also strongly support the initiative from Pirelli, together with the FIA to do this test next week, and then to possibly introduce this new construction from Silverstone onwards.

"Together with the technical directive that has been sent out during Paul Ricard, in terms of what the expectations are, in terms of tyre pressure management, I think it's two very important initiatives in order to make sure our drivers are safe when they go on track.

"Of course, with a change of tyres or construction in the middle of the season, there's always the potential that there's winners and losers from such a change. But I think it's important in such a situation to put our opportunistic view on things aside, priority must be safety. And that's why we support it."

Aston Martin is on top of its tyre management in 2021, and thus arguably has more to lose than most. Team boss Otmar Szafnauer admits that a change in the middle of the year can have tricky consequences.

"It's happened before, I think we've done this before a few years back," the American told Motorsport.com. "And I remember that construction didn't suit us at all. And we went backwards in competitiveness. So hopefully, this time, we'll get on top of the new tyre as well.

"I think we get some information next Tuesday. Hopefully we're going to be running 40 sets of tyres here next weekend [between all teams], and we'll collect a lot of track data from that. Once we have that track data, we'll make a good decision.

"It's a lot of difference for Silverstone. New tyres, plus a sprint. But we'll do it, we'll do a good job."

Sebastian Vettel, Aston Martin AMR21

Photo by: Mark Sutton / Motorsport Images

So what do the drivers think? Obviously safety has to be their priority, and as such, they welcome the change.

"I don't think that the previous tyre was unsafe," GPDA director George Russell told Motorsport.com. "Obviously, we know the reasons of the blowouts. But if there is something that's slightly safer, there's no reason not to take it.

"And so let's see how we get on with that. I'll be shocked there's a big difference, just the integrity will be slightly better."

"If we are doing that for safety, I think we can't complain," said Esteban Ocon. "We have seen tyres breaking, we have seen tyre failures. So it is quite good that we come up with some solutions to fix those problems, especially looking at Silverstone coming shortly. I think this is going to be quite important.

"Until I test it, I can't really give feedback on how it's going to feel. It's going to be interesting, because it's going to re-set a bit the understanding of everyone into the season, as the tyre topic is usually something quite difficult to get right.

Some drivers are hoping that the new tyre could actually be beneficial: "It's only positive for us, just to see if it changes a bit the trend," said Ferrari's Carlos Sainz Jr. "It could help. Who knows? I think our problem is the fronts, but let's see."