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2017 F1 pit stop strategy and selection of tyres (part 1)

Zvonimir Martinčević

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Zvonimir Martinčević: Under F1 cover (eng)

One month ago, the exciting Formula 2017 season ended, so I’ve analyzed what happened with F1 tyres in the previous year. As in 2016, Pirelli offered five compounds of dry (slick) tyres, and two wet (intermediate and full wet tyres) mixtures, and based on what happened in 2016, I pulled some parallels. It should be said that this year a major change in the technical regulation has taken place, and the dimensions of tyres have grown dramatically, and it was not quite enough for Pirelli or for F1 teams to simply apply an improved model for the 2017 season. There are two main reasons for this ; the first is the inability to test the construction and tyre compounds for the 2017 season in 2016, because the test cars, I would say, pretty much couldn’t not even close simulate dramatically changed 2017 Formula 1 cars. Of course, we are talking about the increased downforce and the dimensions of 2017 cars. Another reason is, of course, the change in dimensions, construction, and compound of F1 tyre itself. So none of the important parameters remained the same. In my opinion, it is quite certain that Pirelli went cautiously and conservatively in 2017. And again, this analysis is intended only for “hardcore” fans and Formula1 experts. But let’s move on.

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First of all, we have to say that the dimensions of the F1 tyres have increased compared to 2016. The front tyres grew from 245 to 305 mm (+ 60 mm), while the rears grew more (+ 80 mm), from 325 to 405 mm. The outer diameter of the tyre grew from 660 to 670 mm (+ 10 mm), while wet tyres grew from 670 to 680 mm (+ 10 mm). It is quite clear that the carcass structure of the tyre itself has undergone great changes, and the internal air volume has grown. What remains unchanged is the outer diameter of the rims (13 inches), but the width itself has grown. Thus, 12-inches fronts (304.8mm +/- 0.5mm) rose to 13.7 inches (348.0mm +/- 0.5mm), while the backs grew from 13.7 (348.0mm +/- 0.5mm ) at 16.9 inches (429.3mm +/- 0.5mm).

As for tyre pressure, it is lower in average by 0.825 psi (0.057 bar) in 2017. If we compare the hardness of the 2016 and 2017 compound, I have to say that, as I said before after the first race in Australia (article published on March 28, 2017), Pirelli raised the hardness of the tyre mixture and reduced their wear. This year’s analysis showed that the 2017 ultrasofts were now harder and only slightly softer (but really just a bit softer, if any!) than last year’s supersofts. This also applies to other harder mixtures; supersofts to softs, softs to mediums, mediums to hards. Let us say, however, that this difference can hardly be attributed to the rubber mix as to the construction of the tyre itself . This table, which I conceived, shows the ratio of the softest tyre compounds used in the last two years, 2016 and 2017.

From this chart it is visible how much this year’s tyres were more durable in terms of the mileage driven by the longest stint of the race on a particular mix. In Australia this year the softest tyre was ultrasoft, lasting 17 laps longer than last year’s supersoft, and in the bottom line the approximate hardness of the two blends; so “zero”, this year’s ultrasoft is roughly as hard as last year’s supersoft. Look at the following races and increased mileage comparing to 2016. In cases where ultrasoft, for example, was the softest compound in both races; 2016 and 2017 (in 5 cases), more laps were driven and the hardness grew for  app. +1. The only exception was the race in Azerbaijan where supersoft lasted shorter than at 2016’s race, but it was a chaotic race and many drivers went for 3rd or 4th pit stops (Ricciardo and Bottas, …) to change “free of charge ” tyres during the safety car periods. I’m sure they would last much longer too than those in 2016 if everything went without incident on the track.

But let’s get back to the start, there is also the 2017 Formula1 Tire Strategy chart, which is analogous to 2016 that you could have read last year.

And again I will divide this main table into 6 quadrants, and there are some minor changes as compared to last year. I will briefly explain each of the quadrants. The biggest change I would say is that I used the Pure Pit wall (purepitwall.com) data, which is somewhat better than cliptheapex.com regarding the information about overtaking, or SC laps. It should be said that there are no data for two races in 2016 .; for GP Azerbaijan (Europe) and Austria, so for those races I took data for 2016 from cliptheapex.com. The article 2017 F1 tyre analysis will be published in two parts, just as it was published last year.

Quadrant 1

I started with the number of the race, the date of the race and name of the Grand Prix. Below, from left to right, the name of the driver (I grouped them only as members of a certain team, not in the order of completion of the races). So Ham (Hamilton) at the Australian GP was only 1 time in the pits to change the tyres (ie, strategy of going 1 time in the box). Vettel, the winner of Australia in 2017, went only once in the box, as well, and his chart cell is colored green, meaning his winning strategy of 1 pit stop was the lowest of all drivers. He wasn’t the only one driver in Australia on that strategy, but he was best placed from others with one pit stop strategy. Let’s go back to what the theme today is, therefore, Vettel was the winner in Australia with a one stop tyre strategy, while Kvyat from Toro Rosso was on the 2 times pit strategy and ended as 9th. His chart box is painted in red because he had the strategy of the highest number of pit stops, and as such he was best placed from the others with two stops, like Hülkenberg from Renault. Along with it, they were, at least until Stroll and Magnussen crashed or retired from the race. Of these two, the number of pit stops is in a gray box, meaning they have not finished their race, but their pit stops are counted when the total number of tyre changes scores is counted. This year, Hamilton had seven race-winning strategies with the lowest number of goings in the box for tyre change. On the other hand, Vettel had a four race-winning strategies with the least number of pit stops but also four times the best position in the race with the most pit stops. Wehrlein had four times the strategy with highest number of pit stops, but also he has completed two races with the strategy of the lowest number of pit stops. Of course, his strategy, whatever he did, did not bring him any victory. It should be said that Wehrlein had on average the highest rate of all drivers in 2017, with an average of 1.8 pit stops per race.

Quadrant 2

This quadrant, in addition to showing which tyre compounds has Pirelli chosen for each race, shows us very interesting fact: which driver drove the longest stint on particular compound during the race. In some races, there were more than one driver with the same number of laps, but unlike the 2016 when it mostly happened during the wet races this season it was during the dry races. This year, conditionally, there were only two wet races, the one in China where the drivers started the race on intermediate tyres, and then passed on slick tyres. The second race in wet conditions was this year GP Singapore, but there all the drivers started an intermediate or full wet tyres and then switched on the slicks. This race the drivers used the most different types of tyres this year, five, all 3 slick compounds, and both wet tyres. What all F1 experts this year have been surprised with is the fact that none of the 20 drivers have decided to use the hardest compound of dry tyres on 12 of the 20 races. No one used during the race following compounds selected from Pirelli for the GP weekend: 8 times medium (white) tyres, 3 times soft (yellow), and once hard (orange). And from this it is quite apparent that Pirelli this year “went on too hard” with the rubber compounds.

Quadrant 3

Temperatures of the air ( “Air”) and the track (“Track“) are very important for functioning of certain rubber mixtures. Here, I entered the official data from Pirelli; lowest and highest temperature in degrees Celsius of air and track on Sunday’s race day. The following is information on minimum tyre pressures prescribed by Pirelli for front and rear tyres in PSI (pound per square inch) and in bars. This is very important for the functioning of tyre itself on the track, but unlike the 2016 drivers didn’t object too much about the high tyre pressure set as the minimum by sole tyre manufacturer. Let me repeat the fact from the last year’s GP Abu Dhabi: „Do you remember the Practices at GP Abu Dhabi and Kvyat’s problems with rims? They damaged several times his tyres, not because of an error of Pirelli, but because of the structural faults of the rims on Toro Rosso’s car. Well, it didn’t wonder me so much, but when the Pirelli engineers rampant in the Toro Rosso’s garage on one of the monitors has emerged the data, for which I am quite sure that someone in charge might get a “pedal”. On the monitor there was a detail; tread rubber temperature 92 °C, and the air pressure in the rear tyres 2.6 bar! Do you know which was the minimum pressure prescribed for that race for the rear tyres? See the 2016 chart; 20 PSI or in „our language“ 1.38 bar! So, in track conditions on the track almost double, but it’s no wonder that drivers complain that their tyres are too hard. OK, each tyre has its own speed and load index and the air pressure is one of the most important factors for safe use of the tyres, natural the structure of the tyre itself is “the second part of hygiene.” But twice as much? And, it was only free training without a lot of consecutive laps under tension.“

Let’s go further, in this year’s chart I have entered the symbols of weather conditions during the Sunday’s race. From the table it is apparent that the symbol of sun indicates that the race was run in sunny (warm) conditions, the clouds indicated that the race was run in cloudy weather, but that rain did not fall, etc. Overtakes or numbers of overtakings this year was generally lower than in 2016. There are several different sources, even Pirelli brings its own data. This year, I took over the overtaking data during the race from Pure Pit wall (purepitwall.com).

So there were 14 overtakes in Australia. Next, the number of cars completing the race; in Australia, 13 out of 20 on the starting grid. Next goes the total number of pit stops during the race (Pirelli); Australia 20 total. I added “Pure Pit Stops” the number of clean Pit Stops, so only those cars that ended the race crossing the finish line; Australia has PPSs 15 here. Then, a column in red: “Tyre Strategy” in which the information ratio PPS and the number of cars at chequered flag, ie. for Australia the average number of pit stops of those who have “survived the entire race ” was 1,2. Compared with last year when it was 2,3. Hence, this year is marked (the whole season) with the average number of pit stops during the race 1,5 compared to 2,2 in 2016. Of course, minimum number of pit stops during one race is equal to or greater than 1, because each driver must go at least once to change the tyres. This figure (1) could not have been smaller because it would mean that no driver had finished the race in the event of a complete race. Then follows „the killer“ of all tyre strategies, the total number of laps driven in the race under Safety Car SC. You can do all the strategy preparings you want, but when someone crashes and the Safety Car hits the track all strategies fall into the water, the remaining cars get rid of the mandatory tyre and mount the ones that are better for the race. And at the end, two columns, the winner of the race and race laps needed to be driven during the race under normal circumstances. Vettel won 2017 in Australia, after 57 laps. Of course, some races are interrupted after 2 hours even before the “ideal” number of laps in the race. Although in Singapore this year the race lasted 2 hours, 3 minutes, 23 seconds and 544 thousandths, while last year’s race in Brazil lasted 3:01:01.335. Of course it is (according to FIA F1 Sporting regulations Article 5.3) the distance of all races, from the start signal referred to in Article 36.9 to the chequered flag, shall be equal to the least number of complete laps which exceed a distance of 305 km (Monaco 260 km). However, should two hours elapse before the scheduled race distance is completed, the leader will be shown the chequered flag when he crosses the control line (the Line) at the end of the lap following the lap during which the two hour period ended, provided this does not result in the scheduled number of laps being exceeded. However, should the race be suspended (see Article 41) the length of the suspension will be added to this period up to a maximum total race time of four hours. In Singapore, the total time of the race was over 2 hours, including a run-off time to clear the runway from crashed cars or debris. There is some more options, but I will not go into details of such cases.

Quadrant 4

On the left is the “legend”, followed by the total number of pit stops of each driver during the season. So Bottas had them a total of 26 in all races (including those races which he did not finish!). He finished 19 races out of 20, and below that is the data on the average number of pit stops without those races not completed, it means that his average this season of clean PS for the races completed is: 1,32. Of course, there are also data on all the other drivers. Below is information that the fastest pit stop of this year had the Williams team in Silverstone on the Felipe Massa’s car – 2,02 seconds. Here is a schematic presentation of the dimensions of the F1 tyre with the changes comparing to 2016

Quadrant 5

After a series of numbers for each driver right at the top of this quadrant is a schematic illustration of the thermometer, which indicates the operating temperatures of the tyres in Formula1.

Furthermore, there are two diagrams, the first is called the 2016 F1 TYRE STRATEGY (Pit Stops, Pure Race Pit Stops & Average Pit Stops), which tells us about the correlation of the total number of pit stops at each race, in this diagram we can see the number of visits to the pits for the tyres changes for each GP, and it will well serve us when calculating predictions for 2018 season. Yes, the 2018 tyres will be different, two additional compounds will be added; pink colored hypersoft (the softest) and orange colored superhard (the hardest). About the two new compounds for 2018 more in the second part of this analysis, which will be released on f1puls in couple of days.

The chart below: 2017 F1 overtakes & SC LAPS tells us the ratio of the number of overtakings in the race and the number of Safety Car laps. So far, seems that it does not have some basic connections, although it is clear that in a race in which the number of SC circuits is higher – the closer the cars are placed one after the other, and the greater the chance that someone will decide for an overtaking once the Safety Car went out. SC goes more into favor of those cars that are closer to the back of the grid – back markers, but certainly at least in favor for the driver that leads in the race. Again, with this diagram we have a good foundation for future races at the same tracks, it tells us before the 2018 race itself what we might expect.

Quadrant 6

The last segment of the article tells us which F1 circuit regarding air or the track temperature was the coldest or the hottest and the total number of overtakings and the average number of overtakings per race. Furthermore, there are data of the total number of pit stops and the average number of PS’s, and “pure” Pit Stops (only for those who finished the race). The green is the average number of pit stops, and the total number of SC laps, and in 2017 it was 3% of laps (in 2016 it was 7%) under the safety car, or 60 laps. The last two boxes shows us the number of all laps during the season, and the average of laps per race. Below is a diagram of temperature (working temp. range in °C) of each of the rubber compound in season 2016.

There is no longer statistical data comparison of the overtakings in 2014, 2015 and 2016 seasons due to the change to another data provider, but this year there were fewer overtakes due to the construction of the car for 2017. This year I made an additional table on the number overtakings in 2016 and 2017 season, and as there were no Pure Pit wall data for two 2016 races, I took data of the number of overtaking from cliptheapex.com in 2016. Take, of course, this with the reserve, but even without that it is clear that the number of overtakings this year is considerably smaller (GP Germany wasn’t held), about 30%.

In the table I marked with a light blue color which races were in 2016 and 2017 „rainy“.

The diagrams

1. the diagram of the average number of pit stops for each individual driver and their final position in the championship

If we move out of the diagram Button and Di Resta, which have an average of 0,00 pit stops since two of them drove just one race this year and did not finish it, Giovinazzi remains with an average of 1,00 pit stops. However, he is not very representative as he drove just two races this year (he replaced the injured Wehrlein for Sauber at first two races). Pierre Gasly (Toro Rosso) has the lowest average number of pit stops; only 1,20 per race, and he was placed on 21st place among all drivers, and has only participated at five of the 20 races. Further, Sainz with an average of 1, 25 stoppages (he drove 12 out of 20 races this year), finally ended the season at 9th place overall. According to this chart, Hamilton had an average of 1,30 stops per race and drove all 20 races of the championship, and ended up as the 1st in the driver’s championship. It is clearly that Lewis this year was the absolute best driver on the grid. On the other hand, Wehrlein had the highest average of all drivers; 1,80 and finally finished as the 18th driver in the lineup.

2. the diagram of the number of overtakings, cars that finished the race and the number of SC laps

In this diagram we can generally say that the greater the number of the SC laps, the greater the likelihood that fewer cars will finish the race. An example is the GP Singapore where only 12 cars finished the race and 8 of them somewhere along the way, “crashed”, so the number of laps under the SC was 12. Or the GP Azerbaijan where the number of laps under the SC was 12, and only 13 cars made it to the chequered flag due to the chaotic race. The opposite examples are the GP Malaysia and GP Abu Dhabi where 18 cars finished the race, the SC was 0 laps on the track. Compared to the 2016 season this year we didn’t have any race where all 20 (22 in 2016) cars finished the entire race, like at GP China (6 SC laps) and GP Japan (0 SC laps) in 2016. It is not to be taken literally, I say these are just pure data after the race, and really does not mean that it would take us in the right direction.

3. the diagram comparison of average speed of the fastest race lap for 2015, 2016 and 2017

In this diagram, we can see the evolution of the average speed of the fastest race lap over the past three years with very accurate data from the race. Exceptions are the 2015 and 2016 races in Mexico and Brazil (last year it was raining heavily in Brazil, so the fastest race lap in the 2015 was higher than in 2016). This diagram also confirmed the fact that this year’s cars are considerably faster than a 2016 cars (and tyres, of course) due to the huge technical regulation changes.

4. the diagram of max air and track temperatures during the races

There is nothing special to say, these are just the meteorological facts, but it is worth to know when comparing the results next year, and I will get back on this topic later.

5. the diagram of the drivers who had the longest stint in particular races and particular compounds during the season and their driver’s position at the end of the season

Unlike last year when the “aggressive” Vettel in Ferrari had 8 times the longest stint on certain compounds, in 2017 both Wehrlein and Vandoorne had 8 times the longest stints. The German is the first of this year because he had the longest stints on as many as 5 different compounds; one at ultrasofts, supersofts and full wet tyres, and twice with softs and twice on mediums. 2017 World Champion Hamilton had only four times the longest stints, two times at supersofts and two times on intermediates. He is placed this year among all drivers in this category at 8th place, while the championship second – Vettel with the 2 longest stints on one of the mixes is ranked 18th in this category.

6. the diagram of pit stops, pure pits stops, pit stop strategy and numbers of cars finished

From this diagram you can see the „jumpy“ first part of the season where the number of pit stop rates and clean pit stops are extremely sinusoidal alternating all the way to GP Malaysia towards the end of the season, and after that the jumps are much moderate because the (in my opinion) cars “stabilized” as well as the team’s and driver’s understanding of the 2017 tyres. After that, there was less pit stop and more cars ended races on average. It was similar to the 2016 season, with the exception of GP Brazil when it rained heavily and this fact broke the downward trend towards the end of the season. If this year was not raining at GP  Singapore, this downward trend could be seen sooner, after GP Italy.

The additional 2017 comparisons

This year you can see some novelties in my analysis, which are the tables:

  1. comparison of the softest tyre compounds for 2016 and 2017
  2. comparison of the number of pit stops for 2016 and 2017
  3. comparison of the average numbers of pit stops for 2016 and 2017
  4. comparison of the winner’s pit stop strategies for 2016 and 2017
  5. comparison of the number of overtakes for 2016 and 2017
  6. comparison of the max track temperatures for 2016 and 2017

I have already explained the first table in the text above, as well as the fifth table on the number of overtakings.

The second table compares the number of pit stops for 2016 and 2017

It can be seen that apart from GP Azerbaijan, during the whole season, there was a total decrease in the number of pit stops (here is the data of all pit stops during the race, including those who did not finish the race). Of course, it should be noted that this year there were fewer cars on the grid (Manor had bankrupted, so accordingly there were 2 cars fewer, in 2017 there were only 20 cars on the grid) and a lower number of races (instead of 21 in 2016 there were 20 race in 2017). As for the first facts regarding this year, there we still have had fewer pit stops that even if we had 2 cars more and it would not have much to do with the fact that in total we had less pit stops than last year (from 5 to 41). So without GP Germany there were in 2017 total 523 pit stops, unlike last year’s 869 (with Germany 929). Accordingly, in 2017 there were 346 pit stops less.

In the table – comparison of the average number of pit stops for 2016 and 2017 (Table 3)

it is evident that the trends of the expected lower number of tyre changes have been confirmed due to the new cars, tyre construction and rubber compounds for 2017. Exceptions are the GP Russia and GP Mexico, where last year we already had the lowest number of pit stops: 1,3 just like this year . Of course, this year’s ultrasofts in Russia was much more durable than last year’s supersofts, 13 laps more, while in Mexico the difference between these two mixes was higher; 16 laps. Azerbaijan is the only one in “plus” because of the chaotic race and the “free” pit stops under the safety car periods. Of course, if it were possible and without consequences on the total time the drivers would change the tyres during the race far more than prescribed at least one time, the fresher tyres  have more grip from the older already used ones. In the table, I repeat once again, marked with a light blue color which races were rainy this past year. So, at the end of last year’s we had total of 42.9 (pure pit stops) or average of 2,15 (with 2,18 in Germany) during one race, they managed to reach 30.7 in 2017 (Germany was removed from this statistic) or 1,54, which is 12,2 less or 0,61 “pure” tyre changes on average during one race in 2017

A comparison chart of the winner’s pit stop strategy for 2016 and 2017 shows the relationship between the winner’s pit stops for the previous year and this year.

It is noticeable that out of 20 races, 11 winning strategies were those with less pit stops comparing to 2016, with 8 stoppages identical, out of which on 5 races it could not be lower because in 2016 that number was already minimal, or 1. Only in Azerbaijan, and again only because of the chaotic race there were 3 stops of winner Daniel Ricciardo (last year’s winner Rosberg had one). So, overall (without Germany) in 2016 there were 35, and this year 26 or 9 less.

Interesting one is the last table that compares the max track temperatures in 2016 and 2017

Why is this important? Because if the track temperature is higher, it is better suited to harder tyre compounds. The total average track temperature compared to 2016 went to plus 4.9°C, but look at the difference between Monaco, Canada, Austria, Japan and Brazil (from „plus“ 18.0 to 38.6°C) or in China the difference is in a „minus“ 29.3°C. These are very extreme temperature differences and it is not easy to predict them even if you take perennial average temperatures at a certain time of year when the race is usually held. Some races will change their dates in 2018; Bahrain and China have switched their dates Azerbaijan will be in the time of Russia, and Russia in the period of Malaysian race that has left the F1 calendar. Instead of Azerbaijan at the end of June in the calendar enters France, Austria moved for a week earlier, as did the United Kingdom. Germany is on July 22nd. Other races are mostly in their usual dates.

It will be not easy for Pirelli in 2018 because they will introduce two more slick compounds, but I will review this in the second part of this text (as in the last year). Anyway, next year we will have not only one category softer tyres, but two, because the new hypersofts will be two categories softer from this year’s ultrasofts. I’ll explain this fact in the second part of my 2017 analysis.

Pirelli has already announced compounds for the first three races in 2018 and you will notice that in China the softest tyres are ultrasofts, the medium tyres are the softs and the hardest are the mediums.

About this phenomenon I will refer in the second part of this analysis, but remember, I have blamed Pirelli for the last year tyre policy. Here’s the evidence:

„Personally, I belong to the latter category because it provides an additional interest in this so sophisticated sport, but I think Pirelli has to be more flexible in making decisions about the choice of mixture for each race, and maybe even 3 mandatory compounds, and should not be necessarily linked as ” Siamese twins ” in term of softness, but could be for some races possibly skipped one of the mixture in the series.

This was published on January 7, 2017 and I am not bragging about it, but this is the fact.

Happy New Year’s F1 season 2018!

Sincerely yours,
Zvoc

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Zvonimir Martinčević
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