Valtteri Bottas, Mercedes, Bahrain International Circuit, 2021

Mercedes explain error behind 11-second pit stop which ruined Bottas’s race

2021 F1 Season

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Mercedes have said that a nearly-11-second pit stop for Valtteri Bottas in the Bahrain Grand Prix came down to human error by a mechanic withdrawing a tyre gun too early.

In a video issued by the team, technical director James Allison described the pit stop, which brought back memories of the tyre mix-up which destroyed their chance of victory at the track three months earlier.

Then, it had been down to a radio problem in the garage that failed to communicate which driver would come in first for a double pit stop. This time, however, Allison said it came down to an initial, small timing mistake.

“When the car came into the pit stop box, Valtteri came in very neatly, positioned the car neatly and well, which is always a help for the pit crew. But sadly one of the gun men went onto the wheel, started to disengage the nut, loosened the nut but then started to withdraw the wheel gun just a little bit too soon before the nut had spun off its thread.”

Withdrawing the wheel gun too early causes damage that makes repeating the action to fully loosen the nut harder, Allison explained. “Because it was still offering some resistance at that point, as he withdrew the wheel gun, the socket on the wheel gun started to disengage from the nut and then started to spin round. We call it machining the nut because it starts to chip away at the edges of the nut and destroy the nut, a bit like when you are using a screwdriver and you don’t have it lined up properly, and you start to sort of damage the screwdriver slot.

“So, as he pulled away, the gun machined away at the nut and it didn’t actually come off its mountings.”

Allison said the problem was further compounded by the wheel gun automatically reversing direction, in order to attach the new wheel. “He went back in to deal with it but the gun recognises or is designed to recognise when it has done a ‘gunning off’ action and it automatically shuttles the gun so that it is then in doing up mode and so when he went back on to finish the job of taking the wheel nut off, the gun is now in doing up mode and instead of undoing the nut, it is doing it up again.”

The feature, design to make pit stops as quick as possible, cost Mercedes and Bottas even more precious time. “The subsequent, follow-on mess of that is what causes something which is normally a beautiful two-second pit stop to then collapse into something that haemorrhages lap time and seconds in the pit lane. But all of it was caused by that initial misplacing of the wheel gun, machining the nut as the wheel gun came off.”

The pit stop left Bottas substantially adrift of the race leaders and within an almost-risky margin to Lando Norris in fourth place. Although he was able to re-extend the gap behind him, enough to be able to take another pit stop in the final minutes of the race to go for – and claim – fastest lap, he was unable to challenge for or cover team mate Lewis Hamilton for the lead.

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Hazel Southwell
Hazel is a motorsport and automotive journalist with a particular interest in hybrid systems, electrification, batteries and new fuel technologies....

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29 comments on “Mercedes explain error behind 11-second pit stop which ruined Bottas’s race”

  1. Martin Elliott
    31st March 2021, 18:32

    As well as the psychometric/ergonomic studies for methodology, I’m sure that the teams do proper studies of what could go wrong and how to recover like HAZOP.
    The worry is that they concentrate always on the perfect stop, and don’t fully address the consequences or risk of a ‘misfire’. Historically we’ve seen from damage/time only through to serious injuries to personnel and registered pit media.

    Does the FIA ‘Safety Culture’ which has address the issue at least 4 times in regulations keeping an eye on the levels of risk, or just waiting for the next serious injury/accident.

    1. PRetty much a picture perfect show of how to overoptimize and neglect some risks of failure, isn’t it Martin!

      1. Next thing, the gun has been equipped with a pressure sensor on its face for the reverse function.
        Mistakes happen, it’s what you do with them that matters.

  2. Being a human error then the team should focus on analyzing the scenario and try to minimize the impact for whenever it happens.
    That said, I understand why the team would put Bottas’ performance down to this event, but it was hardly the reason why his race was ruined. He lost a couple of positions at the start that took him a few laps to recover, but once back in clear air he never showed enough pace to get close to the two frontrunners and be in contention for anything other than the lower step of the podium. I can’t remember how far back he was, but it hardly seems like he would be a threat to Verstappen with or without the pit stop issue.

    1. Ben Rowe (@thegianthogweed)
      31st March 2021, 19:55


      as someone pointed out on another forum, bottas’s pace was pretty much equal to Hamilton.

      Leclerc had a great start rather than a poor one for Bottas. Bottas lost one place, not two. Bottas took a bit, but not much time to get by. However, it did cost him a few seconds. He then pretty much maintained the same gap to hamilton – sometimes catching, sometimes falling back. Then it was followed by his 8 second loss in the pit stop. This played into Verstappen’s favour just slightly as had Bottas not lost this time, it was likely Verstappen would have had to do something slightly different to fight hamilton for the win due to Bottas being in the mix. Bottas was only 15 seconds behind Hamilton when he pitted for FLAP. Considering he lost 8 in the stop and a few at the start, it is entirely possible he will have been right on Verstappen’s tail at the end of the race. And actually very likely that the top 3 will have been within just a few seconds of each other. Bottas was in no way better than Hamilton, but pretty much looked as good pace wise. This surprised me given his pace in practice. I do however think that his luck made him appear worse than he actually was. This certainly wasn’t one of his typical days where he was quite some margin off the leaders pace wise.

        1. @balue loving that page. Should be a permanent link to that one. Thumbsup emoji

    2. F1oSaurus (@)
      1st April 2021, 16:22

      @diegof1 Bottas was less than 8 seconds behind Verstappen after Verstappen had his pitstop. So if Bottas lost 9 seconds in the pitstop then that means he essentially lost P2 because of it.

  3. As Brundle said (even last year), if Bottas didn’t have bad luck, he’d have no luck at all..

    1. opps… didnt read before i posted. ;-)

      [ these old yokes are always a pest ]

    2. Martin must be a Cream fan. Or an Albert King fan.

  4. Just think, that could so easily have been Hamilton… and then we’d all be entertaining all kinds of fanciful theories as to why that happened.

    If it weren’t for bad luck, Bottas would have no luck at all. Or maybe you create your own luck.

    1. Racing Dave
      1st April 2021, 12:22

      Or would we all be waxing lyrical how Hamilton fought his way back yo the win with a run of quali laps another change of tyres to battle for the win – Bottas did match Lewis’s pace but where was the fight!

      1. Maybe Bottas is a realist, and has accepted his role is to not take chances with the all important championship points. As a consequence he will manage the engine, not stress the car unless he absolutely has to , or there is something clearly at stake. If there was a real chance of 2nd he might have push harder, but it seems to me he was satisfied with the position. This might not be entertaining, but it is sensible.

  5. Tire strategy and the Bottas debarcle explained here by team Mercedes.

  6. You make ya own look it was no bad luck dropping the ball again and letting a way slower car by. Look at Hamilton when Max passed him off track perfect positioning on way older tyres. Bottas on fresh tyres and with no disadvanatge drops the ball. Can only imagine what he woulda done with Max chasing him down. He probably would of had a huge snap and lost it in turn 2/3. And no Bottas was not as fast especially not the first stint he had clean air aswell when got by Leclerc. Lewis was 2 seconds behind the whole first stint.

    1. The ‘making your own luck’ for a wheel gun operator issue is too silly to comment, and as for getting riled up with Verstappen chasing one down, you now want to pretend your man didn’t get spooked and and went off the track once Verstappen caught up with him didn’t happen. It could easily have been a nasty kerb or gravel trap and 3rd place or even end of the race, but he lucked out it wasn’t. As for pace, Bottas was actually faster on the hard tyres.

  7. Pace. isn’t the determinative factor in WINNING; how Ham responded to the threat and his reactive pace is what won.

  8. RocketTankski
    1st April 2021, 9:09

    You had one job, wheel gun guy!

  9. It might have ruined his race, but I doubt it would have changed the end result. When they told Valtteri to ‘hunt him down’, he only lost time to Verstappen and Hamilton. He was never able to actually be in the battle for the lead.

  10. It’s always bottas, isn’t it, when there’s problems like these, now that’s a number 2 driver.

    1. now that’s a number 2 driver.

      Doesn’t even need to be mentioned. BOT was no.2 before they even signed the contract. Most obvious no.2 in history, the best one too. HAM/Mercedes still owe him 1 win. He doesn’t cry on the podium that somebody stole his win, doesn’t give outrageous interviews about how the team is forcing him to be no.2 etc etc. He’s PERFECT. Ferrari are amateurs at picking no.2s.

  11. Sergey Martyn
    1st April 2021, 12:25

    They have yet to explain last year Russell situation.
    Don’t believe a word

    1. F1oSaurus (@)
      1st April 2021, 16:23

      They did explain that. Quite extensively.

  12. It does highlight just how much of the fast pitstops are down to muscle memory and pure process. As soon as a human has to think to resolve something you start adding thinking time into the mix and very quickly the stop deteriorates. You saw it with the broken nose on Gasly’s car too how they were clumsy getting the car in the air to be able to then change tyres and finally the nose. While they practice the process it is clearly only a fraction of the time they spend drilling the normal pitstop.

    This is always a risk when you’re pushing the boundaries which Mercedes have to do in order to get close to Red Bull. I’ve noticed previously that Mclaren stops are usually closer to 3 seconds and I often wondered if they do so deliberately by not pushing the boundaries to add a bit more safety margin in their stops. Would be interested to see some analysis on average pitstop times across the teams with averages and number of outlier or botched stops that occurred for them.

    1. F1oSaurus (@)
      1st April 2021, 16:28

      @slowmo I know right. it must be better to make sure you always have a good stop rather than winning half a second on a stop. Losing 9 seconds on one stop is enough for half a second on 18 pit stops. Not entirely the same, but still.

      I remember the teams (ie Red Bull) were outraged when started getting a penalty for cars losing a wheel after a stop. The penalty they felt was very unfair. It prompted them to actually take the issue seriously. Like dropping out of the race because you lost a wheel wasn’t enough of an incentive to make sure that never happens.

  13. Why does it reverse direction automatically. The gun could do it by pushing a button while the other two guys are changing the tyre. No time lost or won.

  14. Bottas not only has to fight Lewis but he also has to fight the team. Tough gig.

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