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PIRELLI.COM / RACING

Anatomy of the pit stop

Fail to prepare, and you prepare to fail

There is at least one consistent element throughout the history of any endurance racing series: the pit stop. 

Of course, throughout the decades the operation has been refined and redesigned in response to performance and safety concerns. The outcome is still the same though: fluids replenished, new drivers, new tyres. Go.

And teams have always tried to make their stops as quickly as possible. The faster an operation, the more time there is to react if and when something goes wrong.  

Tyre changes always take place during the refuelling stage of the stop in the Blancpain Endurance Series. Switching used slicks for a fresh set well before refuelling finishes allows for more hands on deck – and able to react if needed – when the car is ready to be released. Or when the fuel line or jack gets stuck.

The pit stop is nothing more than a production line. And so, academics who study the theory of pit stops – yes, such people actually exist – apply established industrial principles such as Ohno’s seven wastes in a never-ending quest to make stops faster and better.

Waste not, want not

Three of the seven wastes – basically, the reasons why processes fail – can be directly applied to the pit stop.

The first one is motion. Ultimately, the less time people spend moving means that the ratio between motion and actual work done is reduced, and in turn so is the overall stop time. Moving less also reduces risk and the chance for things to go wrong.

The second one is waiting. Time spent waiting is time spent doing nothing. But reducing this in a pit stop does requires a lot of time, practice and skill to master – which is why teams devolte so much attention to pit stop practice, Mechanics colliding with each other, dropping wheels and fumbling when mounting a wheel will result in longer wait times and therefore a longer stop.

The third one is transportation. This is all about ensuring that distances parts are moved are kept to an absolute minimum. The logic behind this is similar to waste due to motion: the less time spent moving things; the more time can be spent on changing wheels.

But now that the theory has been established, how is this put into practice?

The evolution of the species

What’s fascinating about pit stops is that there are so many ways that they can be made better, as there are so many different parameters to play with. For the pit stop academics, it’s like a three-dimensional chess game.

One important consideration is the order in which the wheels are changed. An effective order means that the distance a mechanic travels around the car is less than the total perimeter of the vehicle. What tends to work best is starting at the front-right corner and finishing at the rear-right – although there are different ways to do it, depending on the circumstances (and regulations).

It’s an incongruous thought, but the two mechanics changing tyres can easily be compared to competitive ballroom dancers. To be effective they must work within close proximity of each other without colliding and increasing wait times. The most well-drilled duos are an artistic joy to watch when completing their pit stops.

Reducing transportation and waiting in a pit stop can be as simple as having tyres conveniently pre-placed where the rules allow, together with the use of pre-made mounts, so the mechanic can grab the wheels from waist height. Ergonomics and physical fitness play an important part: mechanics have to be fit and flexible enough to work with ease and so reduce the time spent moving.

The same applies to driver changes, as the drivers too become temporary members of the pit stop crew. The driver getting in and the one getting out need to help each other and avoid getting in each other’s way. This can only be achieved with rigorous practice, following an established system.

A well-executed pit stop is an art form, which in an endurance race can contribute to a win as much as the drivers taking to the track. Although in recent years the rule makers in the Blancpain GT Series have focussed on reducing the variance of pit stops due to rising costs (by introducing minimum pit stop times) the stops still form a pivotal part of an endurance race.

Let’s say that finishing a tyre change early enough allows a team to lose an average of no more than four-tenths of a second on each occasion compared to the minimum pit stop time.

Over the course of a 24-hour epic, made up of 26 pit stops, that could warrant an additional advantage of over 10 seconds. In the past, numerous 24-hour races have been won by less than that…

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