Bottas finished second in the opening stint of the Monaco Grand Prix on Sunday and was five seconds behind leader Max Verstappen when he pitted on lap 30 to change tires.
But Mercedes was unable to get the right front tire of Bottas’ car and left it stuck in the pits. Despite the team’s best efforts, the car had to be taken out of service, which ended the Finnish Drivers Day prematurely.
Mercedes technical director James Allison explained how the nut on the axle had been machined by the wheel gun and got stuck.
“If we don’t get the pit stop gun onto the mother completely clean, it can chip off the mother’s drive surfaces,” Allison said.
“We call it the editing of the mother. It’s a bit like using a Phillips screwdriver and you don’t get it right into the screwdriver’s cross.
“You start to round the drive face of the screwdriver slots, and then you just can’t take the screw out of what you want to take it out of because you no longer have the drive faces.
“It is similar with our pit stop nuts when the weapon rotates and the drive surfaces of the wheel nut flake off.
“Given the power of the gun, it can happen that you don’t have a drive face and you just take the mother to a place where there is nothing left, and that is what we had today.”
Allison revealed that Mercedes could not remove the wheel nut from the car at all and needed a heavy duty drill to restore the distance at the factory.
“We didn’t take the bike off, after all, it’s in our garage and the bike is still on,” said Allison.
“It has to be sanded down, taken out a Dremel and painfully cut through the remains of the wheel nut. We’ll do that again in the factory “
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Mercedes team principal Toto Wolff said “many factors” contributed to the problem and refused to attribute it to a single mistake.
“We have to check the design, we have to check the material of our wheel nuts because the mechanics who operate the wheel nuts have to do this in such a way that it cannot be machined,” said Wolff.
“In fact, a mechanic who did that is one of the best and one of the best in terms of pit stop speed that the team has.
“So things always come together. It’s never anyone’s fault, it’s always multifaceted. “
Mercedes wheel nut design
Wheel nut design for the Mercedes F1 W12 by Valtteri Bottas
Photo by: Giorgio Piola
The wheel nut design of the Mercedes (see picture above) does not correspond to that of road vehicles.
Instead, it’s custom-made and dome-shaped. It has two vertical extensions that are gripped by the wheel gun to turn the nut on and off.
It was these extensions that were processed during the Bottas stop and meant that the gun had nothing to grip.
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