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F1 Explained: Why do drivers swerve in a zig-zag motion behind the safety car?

F1 Grand Prix of Brazil
F1 cars can be seen weaving behind the safety car.

It's a common sight to see F1 cars weave behind the safety car during the safety car period. The cars are often seen swerving in a zig-zag motion behind a safety car, and for a new fan, that does not make sense whatsoever.

However, there's a science behind all that. Drivers behind the safety car swerve in a zig-zag motion, as they look to keep their car in perfect condition before the safety car restart. Here are some of the benefits of F1 cars weaving behind a safety car and why F1 drivers do it.


Why F1 drivers weave behind a safety car

Here're a few reasons:

#1 To keep the tyres in optimum temperature window

One of the most important components for the performance of the car is the tyres that are in contact with the track surface. They need to be kept in the optimum temperature window for best performance. If the tyres fall below the working temperature window, the grip is lost, and the driver will not have the confidence in the car to push it to its maximum.

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If the tyres are too hot and exceed the working range, there will be excessive thermal wear, reduced tyre life and shortened race stint. To exacerbate things, the performance extracted from the tyre would not be optimal too.

That's precisely why at every stage of the race, not only during the safety car period, the tyre temperatures are monitored closely, and drivers are kept informed. During a safety car period, that becomes even more important, as the field is bunched together. If the tyres are in the working range, one can attack the cars in front or defend from ones challenging the leader.

The zig zag movement tends to also help in keeping the brake temperature optimum, as most of the time the first corner of a race track is a heavy breaking zone. If the brakes are not up to temperature, it could cause lockups or even incidents.


#2 Clean the debris that might be on the tyres

One of the biggest concerns during a race is the formation of a racing line on the track. A racing line is the optimum path for an F1 car across the track. As the F1 race weekend progresses, the racing line becomes more and more prominent as more and more tyre rubber is laid down on that part of the track compared to other parts.

So with everyone bar @PierreGaslyFr1 on inters, and losing tire temperature to boot behind a Safety Car, the sensible decision was made to stop the race. The heaviest rain is forecast to be now, with it lessening in ten minutes or so. #JapaneseGP

As a result, during a race, this part tends to be the more cleaner part of the track and has more grip. The other part tends to be somewhat dirty with all the tyre rubber falling off the cars as the race progresses. Due to accumulated debris on the sides of the track, whenever an F1 driver goes off the racing payh (to either overtake another car or makes a mistake), their tyres pick up all the debris.

Any debris or dirt on the tyres means a reduced surface area of contact between the track surface and tyre. A reduced surface area of contact means reduced grip while running. So, whenever there's a safety car, a driver weaves in his car to remove any debris on the tyres so that the car would have optimal grip during the safety car restart.


#3 Burn off excessive fuel

F1 cars have an upper limit on the volume of fuel that needs to be used in a race. Not only that, there's an upper and lower limit on the fuel flow rate that could be fed to the power unit. Another added variable in the performance of an F1 car is the weight of fuel.

Excess fuel in the car tends to increase the weight of the car, leading to longer lap time. Hence, it's always a fine balance between the fuel volume in a car, fuel flow rate and loss of performance due to weight of fuel.

These variables are kept in mind when F1 cars are fuelled before the race. Now, during the race, if there have been too many laps spent behind the safety car, the car ends up having marginally excessive fuel in the tank.

This excess fuel could compromise lap time, so to burn it, F1 drivers tend to weave in a zig-zag motion and bring the car back to optimum conditions.

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Edited by Bhargav
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