A little bit of data…
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 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.
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.