Importance of pit stops

As the popular saying in motor racing circles goes, “races are won and lost in the pits”. Le Mans is no different. Clearly, the less time you spend in the pits the better. The new rule that comes into force this season reshuffles the cards in this respect as the mechanics now have two air guns – instead of just one – and can intervene during refuelling, which was previously forbidden.

Why was it forbidden?

Firstly, for safety reasons – to protect the pit mechanics. However, a lot of progress on the equipment has been made in recent years. It was also not allowed for technical reasons to ensure that competitors did not exceed their tyre allocation.

Before each race, each tyre manufacturer communicates a tyre list to the marshals. This list contains all the tyre references liable to be used during the race. Previously, at each tyre change, the pit marshals had to read the bar codes on each tyre to check that they matched the list. Today, the tyres contain an RFID (Radio Frequency IDentification) tag. An automatic reader at the pit lane exit detects in real-time which tyres are fitted to each car as it enters the track. The system then checks the tyres against the list and monitors the quantities used instantly.

New rule

In previous years, no benefit was gained at all from changing tyres on every pit stop as the mechanics had to wait until the car had been refuelled before moving in. The fact that only one air gun was allowed made wheel changes even costlier in terms of time. The rule change should, therefore, result in shorter stops and a greater spectacle for the fans. According to Michelin Motorsport Director Pascal Couasnon, “we should no longer see quadruple stints in prototypes.”

Tyre limits

The new rule will not, however, increase the number of tyre changes as the Sporting Regulations limit the number of tyres that the competitors can use during the race: 48 in LMP1, 56 in LMP2, and 60 in LMGTE Pro and LMGTE Am. Teams may be tempted to try a different strategy, however. “In recent years,” Couasnon continues, “we have become used to seeing cars – especially in LMP1 – do several stints on the same set of tyres thanks to Michelin’s consistency, which meant that they actually used fewer tyres than the regulations allowed, despite the lower allocation. This year, teams could adopt a different approach: determine the number of stints required to complete the race and divide this number of stints by the number of sets of tyres allowed, while remaining within the quota.”

The team strategists will, therefore, have their work cut out to choose the right option at the right time, as Toyota Technical Director Pascal Vasselon pointed out at the ACO media conference: “We’ve set up a special team to look at pit stop strategy. It’s been a real headache for them as there are lots of things we can do while refuelling. We’re listing all the possible scenarios. We’ll drill the pit crews in them all and, at a pit stop during our test sessions, we’ll activate one of them.”

Why not cut the number of tyres allowed?

Quite simply for safety reasons. “We’ve reached a limit regarding the number of tyres allocated for the race,” Couasnon explains. “If there are several punctures due to a track incident, for example, over-restricting the number of tyres would increase the safety risk for the teams.”

Going back to that adage that an endurance race is won and lost in the pits, the #2 Porsche 919 Hybrid may well have disproved the theory last year, triumphing after rejoining the field in 56th position following an hour-long repair due to a loss of front axle power. Nonetheless, despite the rule change, pit strategy will undoubtedly continue to play a key role at the 86th edition of the 24 Hours of Le Mans on 16-17 June.

Photo (Copyright ACO/Nikon): The Porsche 911 mechanics wait for refuelling to finish before changing tyres at the 2017 Le Mans 24 Hours.