Hello everyone.
Let’s go for something a little less controversial this week. Race Strategy.
During an F1 race weekend, you’ll hear things like “we’re expecting one stop strategies
at this track” or “two stop strategies are the norm, but some teams might try and
go for the one-stop”. What factors determine what makes for the best strategy at a given
track and how do teams go about calculating this?
In this video I’m going to go over the basic variables that build towards an effective
race strategy.
Let’s simplify this right down to make it easier to see how everything works. Let’s
imagine a ten lap race. I’m going to draw a bar chart, with the length of each bar representing
a laptime.
Let’s start by looking at different pit strategies with different compound tyres.
Let’s say you’ve got the Soft tyre that lasts for 5-6 laps and gives lap times of
80 seconds and the SuperSoft tyre which lasts for 3-4 laps and gives lap times of 75 seconds.
A pitstop will cost you 25 seconds.
For the moment we’re ignoring all other variables and rules. For now, we keep it simple.
One strategy could be running the soft tyres for 5 laps, pitting and then running the soft
tyres for another 5 laps. Another strategy could be running the SuperSofts
for 4 laps, pitting, running them for another 3 laps, pitting, then running a third set
of SuperSofts until the end. Which is the best strategy?
Well, we can work this out by adding up all the laptimes, plus the pitstops.
The one-stop, soft tyre strategy is 80 second x 10 laps, plus 25 seconds for the pitstop.
That’s equal to 825 seconds. The two-stop, SuperSoft strategy is 75 seconds
x 10 laps, plus 2 x 25 second pit stops. That’s equal to 800 seconds.
In this very simplified model, the two stop strategy is fastest. Now, we build on this.
One thing we need to add into our model is the Tyre Wear Profile. This describes how
the grip level of the tyre drops off with every lap. I’ll go into more detail on how
and why tyre performance degrades in another video but in basic terms, the tyre will be
at its fastest when fresh and get slower and slower with every lap. The way in which the
tyre wears will depend on things such as the compound, the track and the temperature but
we can essentially draw a curve like this to describe how the tyre wear affects the
lap times over time. Faster lap times up front, lengthening over time.
We can see the ‘cliff’, here – when the laptimes start to plummet rapidly. Drivers
will want to pit before this point – in our little model there, the cliff hits around
5/6 laps in and the tyre starts to lose all grip before degrading completely. When we
say the tyre ‘lasts’ around 5 laps, we’re talking about how many laps it can continue
to deliver reasonable lap times. Here’s how the one-stop strategy changes
if we factor in the tyre wear profile It’s easy to see how much time can be lost
due to tyre wear over the course of a race and dealing with this is vitally important.
Now, this model strategy isn’t allowed in real F1. As we know – in modern F1, each
driver has to use two different compounds of tyre (out of a choice of three) during
a race. How you use the available compounds by assembling a race out of a number of ‘stints’
can make all the difference to your result. Let’s extend the model to give them twenty
laps now. This will make the stints easier to see.
Now, an example of a ‘conservative’ strategy might be: start on the supersoft tyre (it’s
almost always best to use the grippiest tyre for the start to get off the line well and
get in the fight for early positions). Let’s say the SuperSoft has 6 good laps in it. After
6 laps you might then take a pit stop and run the medium tyres all the way to the end
of the race. The mediums aren’t amazingly fast but they are consistent and will take
you to the end, meaning you don’t have to take another pitstop.
Alternatively, you might take an ‘aggressive’ alternative strategy: start with the SuperSofts
for 6 laps as before, but then switch to the soft tyre. The soft is faster than the medium
but won’t make it to the end of the race. You plan to take a second pitstop and switch
back to the SuperSofts for a final sprint to the finish. You will be on a faster compound
of tyre than the conservative strategy for 14 laps (that’s 70% of the race!) BUT you
have to take an extra 25 second hit for that 2nd pitstop.
We might find that the aggressive strategy is actually SLOWER than the BUT you might
still use it IF a) You think your driver and car are much
better at managing the tyres than the competition b) You expect some disruption to the race,
like a Safety Car. More on this in a bit.
Now we’ve added a simple model for tyre wear, let’s consider fuel.
There’s no refuelling. The cars are filled up at the start and over the race the fuel
drops, which makes the car get lighter over the race which improves overall laptime (the
car has to expend less energy pulling its own weight around) and makes the cars easier
on tyre wear (we didn’t factor this in before but this could mean that SuperSofts last only
10 laps in the first stint, but could last 13 laps in the final stint). For simplicity’s
sake in our model, let’s just say the car gets faster as it uses up fuel in a fairly
predictable way. BUT, because there is a maximum amount of
fuel the car can use over the course of the race, the car may not be able to actually
run at full pelt for every lap of the race. The car is allowed to use 105 kg of fuel but
running at maximum performance for the whole race may require closer to 200 kg! Not only
that, but fuel weight is SO detrimental to racing speed that strategists might not even
want to fill the car to the brim. This means some fuel management is needed through the
race. The SuperSoft may do those 75 second laps
at full beans but can maybe only do 78 - 80 second laps when conserving fuel and energy.
Managing when to use which engine mode will often depend on what’s happening in the
race, but race strategist will arrive with certain expectations: middle parts of each
stint will probably be fuel conservation times, whereas the start of the race and the laps
around the pit stop phases will be the prime time to go maximum on the power. See the UNDERCUT
video for how this may work to a driver’s advantage.
And then there might be a Safety Car or two, just to throw a spanner into the works.
Safety Car and VSC periods are run slow: the engine will use much less fuel and the tyres
will take much less wear and tear. This means that the more laps that are run
behind the safety car, the harder the cars can run in the remaining laps of the race.
They can take the softer tyres longer. They can run in higher engine modes for longer.
If the SC period occurs here this neutralises these laps which – and bear in mind, I’m
over-simplifying this – effectively chops these laps out of the race. We should almost
ALMOST ignore these laps altogether, meaning we subtract these missing laps off the END
of the race. So in this example, the SC comes out on lap
12 for three laps. At the time, teams were expecting 8 more laps of racing, but now they
only have 5 more laps of racing. The car on the conservative strategy can switch things
up, take a free pitstop and match the pace of the aggressive SuperSoft strategy.
Now, you can’t predict a Safety Car or a VSC but you can make an educated guess. Some
tracks have a high change of a SC (Monaco and Singapore for example) so you might create
some strategies that allow you the flexibility to change things up and switch strategy given
the opportunity, or you might go aggressive with the fuel if you believe you’ll be able
to save some while under the SC.
We’ve covered some of the basic variables that go into building some race strategies
but there are other factors that will need considering along the way.
WEATHER - The weather: variations in temperature and the probability of rain might affect your
compound choices. TOUGH TRACKS - If the track is difficult to
overtake on, you might choose not to go aggressive as aggressive strategies normally require
some overtaking (you take an extra pit stop, which puts you behind other cars. You’ll
need to overtake these cars to exploit your lap time potential)
ROAD BLOCKS - You may even get stuck behind an unexpectedly slower car through no fault
of your own. Jarno Trulli used to be know for qualifying well and not being able to
maintain a good pace during the race, resulting in the infamous “Trulli train” where a
queue of faster cars would get stuck behind him. In cases where traffic comes into play,
you might choose a strategy that puts your car out of sync with drivers that might end
up as potential literal road blocks to your success.
TEAM STRATEGY - Also, a team will often concoct strategies that take into account BOTH of
their drivers: to make sure they are both fairly treated, to keep them out of the way
of each other or to allow the number 2 driver to assist the number one driver in their quest
for title glory. I hope this has provided some insight into
the way that strategies are put together. As the very essence of a race strategy is
always modelling how lap times will unfold, adding those laps together and finding the
shortest way to the end of the race. Simple, really, right?
Right?