Chinese Grand Prix: Strategy Predictions and Friday Practice

Posted on April 13, 2012

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The first two races have been interesting this year in that the qualifying pace has been much slower than 2011 (over 1 second at each race), but the race pace has been less affected – about 0.5s, although the fastest lap in Malaysia was only 0.2s slower than the previous year’s best. This gives us a starting point for assessing the Friday running, and gives some idea of the fuel loads that the cars may be running.

True to form, the fastest lap of Friday practice, the 95.9s lap of Schumacher’s Mercedes is two full seconds slower than last year’s pole position time. The pole time is likely to be somwehere around a the 95s mark (following the trend), which gives of the order of 20kg of fuel in the cars. Which sounds about right. The race simulations are less clear. The early laps from 2011 were run at about the 104s mark, so we would expect laptimes at perhaps 104.0-104.5s from the leading teams on full tanks. The long run laptimes posted by the majority of the teams in Friday practice were in the 103s and 104s ranges. This is about 1-1.5s quicker than would be expected, which would suggest a second stint fuel load in most cases. Either that, or it may be that the conditions suit the cars better as the weather is cooler than last year. Whichever, it seems that the teams are using pretty similar fuel loads, as we don’t see the first stint/second stint fuel load discrepancies as clearly as usual. The other (very) notable thing is that the tyres seem to be lasting pretty well. There are a number of stints of 10-12 laps or more, and the laptimes are holding up very well – indeed some cars are getting quicker through the stints. In Malaysia is was easy to tell which tyres the cars were using based on the laptime degradation – here it is not so clear (except for Mercedes). This suggests that the soft tyre is lasting – I can see no reason why it would not be the race tyre of choice. The gap in pace seems to be of the order of 0.5s, with Di Resta’s stints being the best evidence I can see for this. Pirelli said that this varied a lot from team to team in Malaysia, so we have to be a little careful with this. Rosberg (on softs) was about 0.3s up on Schumacher (on mediums), which gives another (but less certain) view.

So how fast are they relative to one another? Well, if we look at the top four teams, only Button did not provide reasonable data to assess, and the pecking order is:

Hamilton

Webber +0.1s

Vettel +0.2s

Alonso +0.4s (but not consistent so less certain)

Rosberg +0.7s

Massa +0.8s

Schumacher +1.0s (on mediums)

The Ferrari pace is odd – Alonso starts as fast as Hamilton, then is not consistent. Massa is more consistent, yet slower.  They seem to be of a similar pace to the Mercedes in race trim, and there seems to be about 0.5s between the McLaren/Red Bull battle and the Ferrari/Mercedes battle. Of note is that the only team who show real deterioration of laptime through the stint is Mercedes, especially on the soft tyre. I can see them racing the harder tyres preferentially. It seems likely that Mercedes will qualify well ahead of Ferrari, but may be racing them come Sunday.

For the midfield teams, Lotus (who may not be midfield) didn’t do a race simulation as the car was not working well. Brake issues left Perez with no representative run, and Ricciardo’s runs were too erratic to learn much. Of the others, we have (relative to the pace of Hamilton):

Maldonado +0.4s

Di Resta +0.5s (on softs)

Kobayashi +0.5s

Hulkenburg +0.6s

Senna +0.7s

Di Resta +1.0s (on mediums)

Vergne +1.5s (on mediums)

From this it looks like Toro Rosso are a little down on race pace. The data suggests that they are about 0.5s quicker on the softs, but the data is not good enough to be sure. Force India look stronger here – the runs are consistent and the soft tyres are clearly still good after 10 laps at what appears to be a competitive midfield pace. If we compare this pace to the frontrunners, we find that this group slots in between the race pace of the McLaren/Red Bull and the Mercedes teams, at about the level of Alonso. This would not be inconsistent with the previous races – Alonso at the head of a close midfield, and Mercedes struggling and gradually being shuffled to the back of the midfield group. Somehow I don’t think that Mercedes will be as bad, but it seems highly likely that they will be fighting a rearguard action in the race. Could be some fun at the end of the straight.

Of the other teams, only Kovalainen gives us something to go on, and he is about 0.5s down on Vergne – but I don’t know if this is like-for-like or if he is closer to 1s behind, which would be the case if he ran soft tyres. Given the previous races, 1s is most likely.

After all that, the pecking order we get is not much different from what we might have expected from the last races. But we do have about one second between first and sixteenth, so it’s very close. McLaren look strong, Red Bull look good in race pace, and Mercedes look set for a long Sunday afternoon hanging on to as high a position as the can. Force India look better, and Maldonado is surely going to produce a result soon.

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Last year’s race was won by a three stop strategy, overtaking a two stop strategy in the closing laps. In reality, the assessment of the race shows that there was very little to choose between those strategies – I would just favour a two stop, but it was marginal on tyre life. For this year, the harder tyre is only 0.5s (best guess based on today’s times) slower than the soft tyre (last year it was about 1.0s), which changes things a little. In effect, the strategy is very similar to Malaysia, so it will depend on the tyre lifetime more than the lap-to-lap degradation rate.

From the data today, it looks like the soft tyres are lasting quite well on most cars, and ten lap stints have been managed with very consistent lap times. Therefore, I would expect that at least 10, and closer to 15, laps from the soft tyres should be expected. I’ve done the work with the intelligentF1 model, and the results are not as clear cut as you might like, with the dominant factor being the point at which the ‘phase 2’ degradation kicks in. As usual I have used the best model based on the 2011 races, which is to add 0.5s degradation per lap after phase 2 starts.

If 20 laps can be managed on the soft tyre, and the medium tyre can do 25 laps, then a two stop race is 8-9s faster than a three stop. If it is 15 laps for the soft, then a two stop and a three stop are very closely matched – I have the two stop a mere 3.5s faster. If the soft tyres last 10 laps, and the mediums last 20, then two stops, with two stints on mediums is fastest, but two stints on softs is slow. If the mediums only do 15 laps, then three stops is fastest and four stops comes into play. Complicated? You bet, and I think this is just the kind of stuff that Pirelli were aiming for.

To put this in a table:

It seems to me that the safest way to go is to plan for two stops with two stints on the hard tyre. I would be inclined to start on the soft tyre as it does seem likely to do the necessary laps, and if it looks like the medium isn’t lasting, then there is more flexibility in switching to a three stop. There are a few special cases:

– Mercedes will need to use the medium tyre – I guess they are the most likely to go soft-medium-medium.

– Those faster in the race (Sauber, Ferrari) than in qualifying may choose to start on the hard tyre as they mat have their pace restricted in the early laps by those around them, in the hope that these cars would start on softs. This would reduce their time loss in traffic, and give them the best chance of gaining time on a free track by being out-of-sequence with the slower cars.

– Lewis Hamilton. He is clearly fast here, and without his penalty would be looking very good. If he qualifies on softs, he will start on the third or fourth row, if on hards it may well be the fifth row. I think that his likely pace on either tyre will mean that he will be looking to overtake cars – the pace penalty on the medium tyres is not sufficient that he will lose massively less time in traffic. It would be OK if he wanted to play safe – but that isn’t Hamilton. I can’t see other than his qualifying as high as he can on the soft tyre, and using his pace to get as far forward as he can as quick as he can. On a track where overtaking is more difficult, the mediums are an option, but I think he’ll do a standard qualifying using the soft tyres. This would leave a switch to a three-stop open as well.

Roll on qualifying…

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