Mercedes elaborates on their strategy in Turkish GP; why only ICE change
James Allison goes through most of the decisions of Mercedes in Turkey.
James Allison looks back at F1 Turkish GP and how Mercedes fared strategy wise. what they could have done as he adds on the engine situation.
The F1 Turkish GP left several questions to be answered, especially with regards to the strategy decision of Mercedes on Lewis Hamilton's side. The team did wish to pit early on but hung on late after a push from the Brit to stretch the first stint.
They eventually were forced to pit after the lap times started to trim down and they had no choice, but to salvage a Top 5 finish. Although Esteban Ocon did see-through the race without pitting which shows it was possible, but with certain conditions.
There was always a risk of puncture as this was beyond the permissible data and limit from Pirelli, while he would have lost all performance in the final laps, which would have left him to defend against host of other drivers racing just behind him.
Additionally, Allison talks about the surface which didn't dried enough for Hamilton to bypass the inters stop and switch to dry compounds. In hindsight, as Mercedes chief Toto Wolff and the driver already alluded to before, they would have stopped earlier.
Stopping around the time of Perez battle:
Allison: "We did consider undertcutting Perez. But in order to understand why we didn’t do it you have to understand a little bit of the strategist's dilemma. The strategist doesn’t know what will happen in the future, has no guarantees of anything and all the strategist can do is play the best hand that they can. They are trying to maximise the odds, the probability of success but they can't guarantee anything. So, sitting as we were behind Perez, approaching that lap 36, 37 mark with a car that was quicker than Perez but penned in by it. You've got to consider the things that were running through our minds at the time and principally running through James Vowles's mind, our Chief Strategist.
"Yes, it is possible we might have made an undercut but you have to remember that when you come out on fresh Intermediate tyres on a track that is no longer covered in water and is actually nearer to dry than it was to wet then those tyres have to be treated with kid gloves in the opening laps, else they tear themselves to pieces and suffer from what we call heavy graining. So, instead of what you can normally do which is come straight out on new rubber, hit it and get a jump on someone, we would have to come out and then be super careful on that new rubber. So, pretty tough to undercut in those circumstances.
"Set against that two other things, firstly, if we waited and maybe Perez came in then we would then take track position over Perez without having to overtake him. And if we could then hang on to our tyres then that would have been the easiest overtake in the world. That's sitting there in your mind as well. And then the final consideration, it was a drying track perhaps it was going to go fully dry and we would want to go onto slicks.
"The car that could get from Intermediates onto slicks in just one change, that would be a car that would do very, very well at the end of the race. While the opportunity of an undercut was hypothetically there, weighing up those other opportunities against it made us not want to take it and in the end it probably would not have succeeded as an undercut but maybe would have been a good thing to do with the benefit of hindsight in terms of the right point in the race to put new rubber on."
Best strategy then:
Allison: "As ever with strategy, at the end of the race it is always obvious, always obvious to know what would have been the perfect lap because at the end of the race, you have full visibility of what would have happened. However, if we look at it overall, the best lap time to have stopped would have been around the 36, 37 mark that was when Valtteri and Verstappen stopped and had Lewis done the same and then treated his tyres nice and gently, then in all likelihood he would have come in a strong fourth, maybe be able to pressurise Perez for third and perhaps overtake him. That would have been optimum.
"We didn’t do that, we stayed out for longer than that hoping that the track would go dry, hoping for a little while that the tyres would last, that they would hang on and we would get the easiest third place on offer at the time simply by inheriting it from those that did do a pit stop. But a few laps into that extended run, when all the other people had stopped and with Lewis's tyres going south pretty rapidly, it became clear that we wished we had stopped a bit earlier. Now, I think the optimum would have been 36, 37 by the time we realised that we should have made that stop then and we were looking to cut our losses it was round about lap 41 and that too would have been okay, that would have been a fourth-place type of stop.
"In the end we pushed on a bit longer than that, another nine laps with the tyres degrading all the while and when we eventually did call Lewis in it was because the lap time chart that we use to make our predictions was telling us that it was not looking good for hanging on to the end of the race. That the car’s pace by then would be sufficiently poor that he wouldn’t hang on to the place that he was holding at the time and we were looking at something that was somewhere in the region of seventh, eighth place based on the way in which the tyres were progressively degrading.
"Now, if you gave some sort of fairly heroic assumptions about the what the tyres would do from the lap where we did eventually come in, lap 51, if you said from that lap forward, they would suffer no further damage as a result of the remaining laps in the race then you could just about convince yourself that Lewis would have come fourth rather than the fifth he did come. However, that is a pretty heroic assumption, because actually the tyres were just slipping more and more and degrading more and more. If you put a more realistic prediction of what would have happened, then you see that Lewis would have come in around about the seventh place, possibly even eighth.
"So, the strategist's choice, always trying to give you the best option, is looking at that and thinking: Well, I've got very low odds of being able to hang on to fourth, no chance at all of hanging on to the third I am currently in and highly likely to be seventh with an outside chance that I might be eighth, but if I come in I am easy peasy going to secure fifth. And you can see why if you are playing a hand of poker like that, you are going to choose the best option and the best option for us, having missed out on the earlier call, was to come in and secure that fifth place which is what we did."
Going to the end:
Allison: "I think the answer to that is: Would we still have had inflated tyres that would be capable of going around the track? Yes, in all likelihood, we would have got to the end of the race on one set of tyres, able to circulate without difficulty. Other cars did that, Ocon did that for example. And our car typically runs its rubber better than many of our competitors. So, yes, we would have got to the end of the race.
"The question is, how quick would we have been? And the evidence there is pretty clear: We would have been very slow. The tyre was using its rubber throughout the entire race and towards the end as the track approached dry but never quite got there, than that wear accelerated. And Lewis's lap times were starting to get worse lap by lap by lap and while he would have made it to the end of the race, the pace would have been quite dismal by the time he got there."
Dry tyres ever possible:
Allison: "The answer is that although you are right, the tyres had in fact worn away all of their sort of grooved tread pattern, it didn’t mean that the slick rubber would have been okay because there was no dry line on the track. The humidity of the day, the sort of continuous presence of drizzle in the air, the temperature of the day meant that the track temperatures and the sort of general moisture on the surface would have meant that if we had come out on slicks, as they left the pits all nice and hot from their blankets very soon after, a corner or two afterwards, they would have dropped in temperature down below the level at which that rubber functions.
"Because the dry tyres aren’t just dry tyres because they don’t have tread, they are dry tyres because the rubber is fundamentally designed for going at a certain speed, having a certain amount of energy put through it and therefore operating at a much higher temperature than the Intermediate rubber was. So, although the Intermediate rubber had worn away to near slick, its temperature is much, much lower than the dry tyre would have been.
"So, the Intermediate tyre as a slick is able to grip the track because it's a softer rubber, able to operate at those lower temperatures. Put on a proper dry though and head out on a greasy coldish track in those humid conditions, all the temperature would have gone after a corner or two and it would have been a disaster. And indeed, the one intrepid driver who did try that, Sebastian Vettel, very quickly found that out."
Surface not drying quickly:
Allison: “Two years running at Istanbul and two years where the track threatened to dry but never quite did. I think actually last year it eventually did, but this year it ran all the way through with us thinking at the beginning of the race, 15 laps and it will go dry and then 15 laps in we were thinking another 15 perhaps and it will go dry and even when the leaders of the race were stopping and Lewis was pushing on, on that set of Intermediates from the start of the race, trying to see if he could hang on, the main thing that was motivating us was hanging on because it was going to go dry.
"And of course, it never did, it never did go dry. This is just a feature of the ambient weather conditions with the moisture in the air, the low sort of persistent drizzle here and there throughout the day in a very, very humid environment on a track surface that is a very, very smooth asphalt that sort of doesn’t drain away or wash away quickly on a surface which itself is difficult for the tyres to grip unless the temperature of the tyre can be held very high and of course difficult to achieve that high temperature for a slick rubber when the track is sort of cold and greasy in that ambient conditions. All the way through all the teams will be thinking to themselves: It's going to go dry, it's going to go dry! But it never quite did."
Engine situation, no other parts changed:
Allison: "I'm going to get to the answer of that but I need to just give a bit of background first. The so-called power unit, the entire device that propels the car forward is made up of seven different components. The ICE, the Internal Combustion Engine, the Turbo, the MGU-H, the MGU-K, the Energy Store, that's the battery, the Control Electronics that go with it, and the Exhaust System - that's seven elements. Each of those seven elements you are allowed limited quantities in an entire championship.
"If you replace any of those seven elements above the maximum that you are allowed, then you take a penalty and you take a ten-place penalty for each of the elements that exceeds its permitted number. In our car we know that it is going to be a challenge to get to the end of the year with the Internal Combustion Engines that Lewis had, the three that he is permitted. So we had to choose a moment where it was judicious for us to introduce a new one to give us a good shot at running to the end of the championship in good shape. Now, we could of course have replaced the entire power unit, but if you do that then you are replacing each of those seven elements, taking ten places for the first and then ten places for the second and then of course you are at the back of the grid.
"So, the moment you take more than two elements you are at the back and you might as well take all the others to go with it. But in our case the area that we wanted to give the maximum amount of reassurance to us over the remaining part of the season was the Internal Combustion Engine. And if we limited our change to just that then we could take just the ten places, not be at the back of the grid and then our biggest worry at that point would just be the heart in the mouth that we would experience at the start of the race keeping our fingers and our toes crossed that Lewis would get round that first corner safely. And indeed, that was a very tense moment for all of us in that damp and slippery start and it was a great relief to see him emerge unscathed around that first corner."
The Finn didn't think to not stop.
[Image courtesy: Daimler Media AG] [Note: This story was written on FormulaRapida.net]