Formula 1’s latest technical controversy has erupted at the Brazilian Grand Prix amid suspicions that some teams have allegedly used water to cool their tyres from the inside.

With the fight for the championship between Red Bull and McLaren getting super close, there has been an increased probing between the two squads over elements of their cars.

McLaren came under fire for its mini-DRS rear wing, which the team had to alter in the wake of complaints about the concept being outside the rules.

Then more recently there was a row over Red Bull having a front bib adjuster inside its car that some of its rivals suspected could have been used to adjust ride height during parc ferme conditions.

Both matters brought intervention from the FIA, but neither squad was found to have done anything illegal.

Now, however, Motorsport.com has learned that attention has shifted to a trick that Red Bull suspects has been used by several of its rivals – believed to include McLaren – to help cool tyres during races.

The theory is that some teams have found a way to inject water – or another unspecified liquid – into the tyres through the valves shortly before tyres are fitted to the cars in the race.

Having such a coolant inside the tyre could help keep the bulk of the tyre cool to help limit thermal degradation, and ultimately help deliver better race pace.

It is understood that concern about the activity erupted after the Singapore Grand Prix when sources suggest some rims of teams were spotted with liquid inside them – something that is unusual.

That is because teams normally make an extra effort to try to remove all moisture from inside a tyre as that helps to ensure teams can hit perfect peak tyre pressure.

Indeed, F1’s technical regulations make a point of trying to limit the amount of moisture that teams can remove rather than add.

Article 10.8.4 states that: “Tyres may only be inflated with air or nitrogen” and “any process the intent of which is to reduce the amount of moisture in the tyre and/or in its inflation gas is forbidden.”

Motorsport.com has learned that the FIA has been alerted to the concerns about the activity, and its head of single-seater matters Nikolas Tombazis has been in dialogue with Pirelli and teams at the Brazilian GP to discuss the matter.

Red Bull Racing Team Principal Christian Horner talks with Nikolas Tombazis, FIA Single Seater Director

Photo by: Red Bull Content Pool

Furthermore, it is understood that Tombazis kept a close eye over the removal of the tyres from their rims after the sprint race in Brazil to see if there was any evidence of unusual liquid there.

Although there has been no official comments from the FIA over the matter, it is understood that there is scepticism about whether or not teams would be trying to exploit matters in this area.

The FIA scrutineering report from the sprint race also confirmed that tyres were inspected, and given the all clear. It said: “The tyres used by all drivers during the Sprint today have been checked.”

It is understood that the idea of adding moisture to tyres has been outlawed for many years through a technical directive that the FIA issued previously, so anyone found to have been adding liquid in this manner could risk being reported to the stewards.

The race pace mystery

Red Bull has been hunting for answers as to why its race pace advantage over rivals disappeared this season – especially at the Miami GP where a number of other squads made a leap that could not be explained through upgrades.

Max Verstappen said ahead of the Brazilian GP that the long runs of rival teams are hard to fathom.

Oscar Piastri, McLaren MCL38, Lando Norris, McLaren MCL38, Charles Leclerc, Ferrari SF-24, Max Verstappen, Red Bull Racing RB20

Photo by: Sam Bloxham / Motorsport Images

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“Some teams made huge steps on race pace, which is quite odd,” he explained. “Because if you look at our car compared to last year, we made steps in qualifying and in the race.

“The others also make a decent step in qualifying pace, but then they make a much, much bigger step in race pace. And that’s something that’s hard for us to understand.”

Team principal Christian Horner told Motorsport.com recently about the swing of form in Miami: “If one was a sceptic and somewhat paranoid, you say something’s changed. Because even when we’ve gone back to the configuration of the car that, for example, we had in China, we still have some of the same issues that we have experienced.

“But, in saying that, it changed for everybody, potentially. But I’ve never in a season seen a swing so exaggerated. Obviously we have to get on top of that. We have to understand it.”

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After setting the fastest time early in practice, things went very wrong for Denny Hamlin. The car fired off into Turn 3 as a high rate of speed, spinning sideways and backing into the outside wall.

“Stuck throttle! F****** stuck throttle!” exclaimed Hamlin the radio. There was significant damage to the rear clip of the car. Hamlin drove the wounded No. 11 Joe Gibbs Racing Toyota back to the garage. As he climbed from the car, he slammed his helmet down on the roof in frustration.

Denny Hamlin, Joe Gibbs Racing, Toyota Camry

Photo by: Bozi Tatarevic

After narrowly missing out on the win at Homestead, Hamlin enters Martinsville 18 points below the cut-line. It would have been difficult, but he could have pointed his way in with the benefit of stages, but that path is likely gone now. Unless something surprising happens to the Hendrick Motorsports drivers in front of him, a win may be necessary on Sunday.

He will not take part in qualifying and will start from the rear of the field. And Martinsville is a track where passing is difficult and those in the back are lapped rather quickly, so this really puts him behind for Sunday. The team has the choice to either make repairs to the primary or go to a backup for the race. At the moment, they are trying to fix the primary and will run it through inspection to check the measurements.

Hamlin was the first driver to miss out on the final four in both 2022 and 2023. He is the winningest driver in NASCAR Cup Series history without a championship as well. It’s a glass ceiling he simply cannot seem to brea and a myriad of issues have plagued him throughout the playoffs this year.

Joey Logano  and Tyler Reddick are the two drivers locked into the title-decider at Phoenix with Christopher Bell +29 points and William Byron +7 points on the cut-line.

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McLaren has admitted its approach to team orders is making life difficult for itself, but says there is no “easy solution” that does not risk upsetting one of its drivers.

The Woking-based squad successfully came through the Brazil sprint race with a 1-2 finish, having swapped it cars around to help Lando Norris’s quest to win the world championship.

But the situation was far from straightforward as, with Norris stacked up behind Oscar Piastri earlier in the race, the team risked the Briton being exposed to attack from Charles Leclerc and Max Verstappen right behind him.

While the occasional window appeared to open up in the early stages of the 24-lap sprint to get Piastri to let Norris through, the team kept them racing until two laps from home – when the risk of a Virtual Safety Car for Nico Hulkenberg’s stranded Haas forced its hand in getting the swap done.

McLaren was fortunate that neither Leclerc nor Verstappen were able to stay right with Norris though, because having not switched its cars earlier there was a danger of it never having an opportunity to do so before the chequered flag.

Team principal Andrea Stella has admitted that the team orders situation is a difficult one to manage – but points out that there is no solution that will keep the team and both drivers perfectly happy.

“Making life difficult for ourselves is natural, because when you have two drivers that can win races and a car that can win races, this first thing you have to accept is there’s not an easy solution,” he told Motorsport.com.

“That already sets you in a good mindset to deal with the potential difficulties.

“But, like I have said already in the past, we have worked very hard to put ourselves in this difficult situation – and we are all on the same page: team and drivers.

“I always discuss with the drivers, and say that this is the most difficult thing we are going to face in our career, because this is the only thing that we cannot face by having our interests exactly matching.”

Oscar Piastri, McLaren F1 Team, 2nd position, Lando Norris, McLaren F1 Team, 1st position, congratulate each other

Photo by: Steven Tee / Motorsport Images

Why McLaren delayed the switch

McLaren went into the Brazil sprint crystal clear that the ultimate intention was to have Norris finish ahead of Piastri.

However, what was not settled was how that would be executed in the race, especially because the team could not be certain about how its rivals would get involved.

Explaining how its calls played out, Stella said that the team had agreed with both drivers that they race away as normal – with the priority being that they do not allow any other cars to get between them.

The idea then was to swap the cars once the pair had got to the point where there was a big enough gap behind Norris, so that race-leader Piastri would not be at risk of being overtaken by anyone else.

Stella added: “We knew that we wanted to swap. But we were waiting for the right gap behind Lando, because if you swap and the other car gets in the DRS, we may compromise one of the principles, which is maximum result for the team.

“So, we were observing, and we were ideally waiting for a couple of seconds [gap], but repeated for a couple of laps.”

Stella said that without the gap behind Norris staying large enough for several laps, it felt the risk was too much to force a change too soon.

“The gaps in the sectors were moving around a bit, and I wasn’t completely comfortable to expose Oscar to Leclerc, because, at some stage, Leclerc didn’t seem slow at all at the start of the race.

“Even the time the two seconds appeared, the next lap, it was 1.2 seconds. We were waiting for the right opportunity.

“We didn’t want to get excited and then create a situation that doesn’t maximise the result for the team. We knew that we had time to do that, unless there was a risk of a safety car.

“And as soon as we saw the risk of a safety car towards the end of the race, then we needed to accelerate the process.”