Kimi Antonelli has chosen ballast over the cooling vest for the Singapore Grand Prix, and the reason runs back to a session in Austin last year that left him with heat stroke. Mercedes have made this trade before at heat-hazard weekends, and the championship leader is sticking with it at Marina Bay.
The system itself is not optional for the car. Teams are required to fit functional cooling hardware whenever the FIA declares a heat hazard, which the sport’s governing body has done again for this weekend. What the driver chooses is whether to wear the vest or absorb a 0.5kg ballast weight in the cockpit.
Antonelli told reporters his hesitation is rooted in two failures last year.
“The first time it didn’t work for as long as we had hoped. The second time, the pump system failed,” he said.
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That second failure came at the 2025 United States Grand Prix in Austin, where the system never cooled anything.
“I did the whole session with the system pumping the water at 50 degrees, so I suffered heat stroke after the session.”
The scenario he described in Singapore is a race where the pump quits early and the system turns against the driver.
“Imagine on Sunday, you put it on, and after three minutes it doesn’t work anymore and just hot water is even worse.”
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His answer, for now, is physical rather than technical.
“I’m going to train hard, so I don’t have to use it for the weekends.”
Marina Bay heat hazard, again
The FIA’s heat hazard clause under Article B1.5.10 of the sporting regulations kicks in whenever the forecast heat index tops 31°C in a session. Marina Bay sits comfortably inside that threshold, with ambient temperatures in the 30s and humidity typically between 70 and 90 per cent. Drivers lose three to four kilograms of body fluid across the race distance.
Where a driver opts out, the car carries 0.5kg of compensating ballast. During practice and qualifying, teams add 2kg for the cooling hardware; an additional 5kg is required on race day.
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Where Russell and Verstappen stand
Antonelli’s team-mate George Russell is at the other end of the debate.
“I definitely see a benefit in it, I really like it,” Russell told reporters, adding that he would wear the vest at every race except cold events such as the Las Vegas Grand Prix.
Max Verstappen, sixth in the championship, is firmly against.
“For me, it’s not needed. Yes, it’s hot, but it’s not a sauna,” the Red Bull driver said.
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“With this cooling vest, you have these stupid cables in your car, so you’re just limiting your movement as well.”
Antonelli leads the 2026 drivers’ championship on 320 points, 84 clear of Russell and 132 ahead of Verstappen, with six rounds remaining after Singapore. The race starts at 8pm local time on Sunday, 11 October, over 62 laps of the Marina Bay Street Circuit.
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