Why do Mercedes suspect Russell’s race-winning strategy led to his disqualification? · RaceFans

George Russell won praise for his role in an audacious strategy which put him in front at the Belgian Grand Prix.

It also won him the race – for around two-and-a-half hours, until he was disqualified. A post-race investigation discovered his Mercedes was one-and-a-half kilograms under the minimum weight limit. That’s an infringement of the technical regulations and the penalty was never likely to be anything less than disqualification.

After the race Mercedes admitted they had suspicions that Russell’s strategy had contributed to his disqualification. While their closest rivals all made two pit stops, Russell gambled on making it to the end with just one.

“It’s really tough for George to have been disqualified from the win after such an impressive drive,” said Mercedes’ trackside engineering director Andrew Shovlin. “He did a brilliant job to hang onto the tyres and defend to the finish.

“We don’t yet understand why the car was underweight following the race but will investigate thoroughly to find the explanation. We expect that the loss of rubber from the one stop was a contributing factor, and we’ll work to understand how it happened.”

Tyres shed rubber as they wear, forming the off-line ‘marbles’ which drivers are at pains to avoid. The loss of rubber means they become lighter, which is a factor the teams have to take into account in order to ensure they stay above the minimum weight limit.

None of this is new to teams, so Mercedes’ suspicions about the role Russell’s strategy played in his disqualification may seem surprising. After all, Russell used a one-stop strategy in the Belgian Grand Prix last year, so surely Mercedes should have been alert to the potential implications of doing so again?

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This isn’t the first disqualification for a Mercedes car in recent history. Last year Lewis Hamilton lost his second place finish in the United States Grand Prix when his car’s plank failed a post-race thickness check.

On that occasion the team blamed a mistake in its set-up choices due to the lack of practice time available on a sprint race weekend at the bumpy Circuit of the Americas circuit where the ride height setting is particularly critical. A shortage of relevant data may have been a contributing factor this weekend.

Mercedes ran a new floor specification on their cars during Friday practice. They weren’t happy with its performance, so reverted to a previous version from Saturday. There was no dry running on the second day, however. No team had a complete picture of how their car would perform, but Mercedes’ was potentially less clear.

A complication all teams had to get their heads around was the track surface at Spa, half of which had been re-laid since the previous year. Degradation appeared to be high on Friday, then a solid day of rain on Saturday removed all the rubber which had accumulated.

Teams therefore expected a harsh surface on Sunday would which subject the tyres to high strain. A two-stop strategy looked like the way to go and Mercedes thought any deviation from that would involve more stops, not fewer.

But as the race unfolded and the surface rubbered-in, teams discovered the tyres were lasting longer than expected. Russell hesitantly began to consider a one-stop strategy even though it went against what they’d discussed beforehand.

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“It was quite back and forth over the course of three laps,” he said. “It’s difficult because when you feel something in your gut, you have to go with it. But when every single driver and team is pitting to go on to a different alternative strategy, and after all the data we had on Friday suggested a one-stop was not even close to being viable, you do kind of question that a couple of times, thinking, ‘are we missing something here?’ Like, why isn’t anybody else doing this?”

Russell may have been emboldened in his decision as he was among a minority of drivers who used a one-stop strategy during last year’s race. But the circumstances were different then, even though the build-up to the race saw even more wet running than this year. The track surface was much less of an unknown quantity and degradation was so much lower teams were content to run the softer compounds. Russell ended his race with a 21-lap stint on C4s (softs) last year compared to 34 laps on C2s (hards) this year.

Mercedes did not run the hard tyres during practice, meaning they lacked crucial information on how it performed. McLaren and Ferrari did not run it either. Among the front-running teams only one did: Red Bull.

After Russell’s disqualification, Red Bull team principal Christian Horner was in no doubt the rubber Russell lost on his one-stop strategy could have brought that car’s weight down sufficiently for him to fall foul of the minimum weight limit.

“Absolutely, I’m sure that you would have lost well over a kilo of rubber,” he told Sky. “We saw that on Friday.”

Only one other driver one-stopped today. That was Fernando Alonso, who also ran the hard tyres in his final stint, though switched to them three laps later than Russell. He had run the hard tyres in practice, however, so Aston Martin would have known more about its wear rate.

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So Russell was the only driver attempting a one-stop strategy with such limited knowledge about the tyre’s performance. Had Mercedes realised what trouble he was in, they might have warned him to moderate his pace, but he appeared to receive no such message.

Mercedes were arguably unlucky to find themselves in this situation at Spa, the only track on the calendar where drivers do not perform a victory lap after taking the chequered flag. They are directed into the pit lane exit instead. Consequently, they have almost no opportunity to drive on the tyre marbles, picking up discarded rubber which helps them meet the minimum weight limit. However all teams have to take this into consideration at Spa.

The FIA’s explanation for Russell’s disqualification revealed the interesting detail that his car was on the minimum weight limit of 798 kilograms before its fuel was removed. But the regulations state it must pass the minimum weight check “without fuel”, and once Russell’s W15 was drained its weight fell to 796.5kg.

“You have to carry enough fuel to be able to do the sample, otherwise you’re using fuel as ballast,” said Horner. “So, really, sad news for George but obviously a mistake in their calculations.”

“We won’t be making any excuses,” said Shovlin. “It is clearly not good enough and we need to make sure it doesn’t happen again.”

Coming within 12 months of Hamilton’s disqualification in Austin, it was a galling blow for Mercedes. At least on this occasion they had the consolation of Hamilton’s car, which two-stopped to second place, able to inherit the win.

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