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A little bit of data…

By saltire | 28 Jun 2011 | 6 Comments | 2,339 views

It’s been a while since I’ve done some statistical analysis so having been fascinated by a comment from Reboot in Viva’s forum I felt the need to investigate further. I couldn’t recollect any specific examples of traffic having held Hamilton up after a pitstop so it was off to the FIA’s timing data to see if there was anything obvious that had happened, however the initial look revealed that the pitstop times of the two drivers were very similar. So what had caused the discrepancy?

“I was looking at the lap time chart comparing Webber and Hamilton. Comparing the pit stop out lap between the two (they stopped on a similar pattern) Hamilton lost 6, 8 and 6 seconds (=20s). I know the second Hamilton stop was a bit tardy but can anyone explain this? I don’t recall him being unlucky with traffic, was the McLaren just slow to get the tyres working? With a 2s loss at the start this is most of the race deficit to Webber”
Reboot

I decided that instead of just comparing Hamilton and Webber’s times I’d see if the differences held out across teams – so each Red Bull, McLaren and Ferrari driver in included in the analysis. Using each drivers’ pre-pit lap time as an internal control, it becomes irrelevant whether one driver pits on lap 12 and another on lap 14 as we are comparing before with after or like with like. What I found was (I think) quite surprising and perhaps gives some insight into how the different cars behave on the Pirelli tyres.

I should probably explain a little bit about the table that follows before describing the data. For each driver I’ve noted the pre-pitstop lap time, the pitstop laptime and the laptime for the lap immediately following the pitstop, for each of his three stops. Each driver started out on option tyres, made two pitstops for further options and their final stop was for prime tyres. The time loss for each pitstop is simply the difference between the laptime before pitting and that afterwards; the post pitstop time loss is based on the difference compared to the pre pitstop lap time.

Viva F1

It seems that the Red Bull is able to make better use of the tyres on the lap that includes the pitstop, being on average about 6 seconds faster than either McLaren or Ferrari, this accounts for the time difference that Reboot observed between Hamilton and Webber but it was looking at the lap after the pit lap that was most fascinating. On this lap both Red Bulls were slower than on their pit lap. This happened after each driver’s three pitstops and, it didn’t seem to matter which type of tyre they changed to. Conversely, the McLaren’s and Ferrari’s managed a faster post-pitstop lap after every stop, making up most if not all of that 6 seconds they lost out in the pitstop lap. This colour highlighted data in the table shows that McLaren and Ferrari were more than 10 seconds faster than Red Bull on this lap.

Looking at cumulative data (the sum of the time lost for the 3 pitstops) we find that the McLaren’s have less pit loss time than Red Bull with Ferrari the slowest of the group; Button had the shortest pit loss, followed by Hamilton and then Vettel. In essence, the assumption that Hamilton lost out to Webber after each pitstop would seem to be wrong, at least using this method of analysis.

By the 2nd lap following the pitstop all 3 teams have recovered the time they lost for the pitstop and are setting faster laps than before they changed tyres, indicating that whatever is happening with the tyres is a transient phenomenon. I must admit I’ve no idea why the Red Bull’s get more speed out of their tyres immediately after a stop than the Ferrari or McLaren’s but whatever the reason they then fail to capitalise on that gain on the following lap, perhaps that’s something we should be grateful for given their pace thus far this season. I’d be interested to hear your suggestions as to why this should be the case either in the blog comments or in the forum.

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6 Comments »

  • Reboot

    Very interesting.I find it difficult to understand the reason for the differences with RBR. I suspect there is some simple fact that we are missing.

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  • Rick

    Is n’t it all to do with pit position and start/finish line?

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  • Mav

    I suspect there is some simple fact that we are missing.

    Yes there is.

    “Cumulative Loss, both laps” tells the story which you’ll notice is pretty constant across the board. The simple reason is the positioning of the garages relative to the timing line. Everyone bar Red Bull were changing tyres just before crossing the line while Red Bull were doing theirs after the line. Therefore the time actually stationary is added to Red Bull’s outlap and the inlap for everyone else.

    This is all because pitting is determined by the lap they enter the pitlane on, not the one they enter their respective pitbox.

    This is all related to Schumacher serving a stop-go penalty after crossing the finish line (Silverstone ‘98)

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  • saltire (author)

    Mav,

    Seems a bit silly to have one teams’ pitbox on the opposite side of a line than the others. Can’t see how that’s related to Schumi but then again I don’t remember that race.

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  • Mav

    Can’t see how that’s related to Schumi but then again I don’t remember that race.

    Schumi’s pitbox was on the far side of the finish-line – meaning he spent his 10 seconds stationary after the chequered flag. If he’d had to do it before the chequered flag, he’d have finished 10 seconds later (still in first place though – a much overlooked fact)

    that’s why they now have time penalties awarded in the closing laps

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  • Mav

    Seems a bit silly to have one teams’ pitbox on the opposite side of a line than the others.

    doesn’t really affect anything though. the pitlane loss is the pitlane loss whether it’s predominantly on the in-lap or the out-lap

    just remembered that they closed a loop-hole this year – last year, Mclaren could have pitted on the very lap and used their obligatory second tyre compound for just the few metres remaining before the finish line!

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