Race strategy:
fuel and stops

Working out the fuel

It's the simplest part and the one that ruins the most races when done by eye.

The formula

You need two numbers, both of which come out of any practice stint:

• Fuel per lap — how much you burn on a lap at race pace.
• Race laps — if the race is timed, divide the duration by your lap time and round up.

Multiply and add margin. With round numbers: burning 3 litres a lap over 30 laps is 90 litres, plus one or two laps of margin — so 93 to 96.

The three classic mistakes

• Forgetting the formation lap. It uses fuel, and in some formats quite a lot.
• Calculating with your qualifying lap. In the race you're slower, you do fewer laps, but consumption differs too. Use a long-run figure, not a single lap.
• Not counting the extra lap. If the clock hits zero mid-lap, you still have to finish it. Always round up.

And the other side of it: fuel is weight. Twenty litres too many costs you a few tenths a lap for the whole race. Margin yes; brimming it just in case, no.

When to pit

If the rules set a pit window, the decision is inside that window. If not, three factors decide:

• Range. The hard limit: you can't run longer than the tank allows.
• Degradation. If your laps are half a second slower from wear, every extra lap is half a second given away.
• Traffic. Coming out of the pits into a group of slower cars can cost more than the whole tyre advantage.

The most useful rule of thumb: pit when the loss per lap equals the gain from stopping. If fresh tyres are worth a second a lap and there are ten laps left, you have ten seconds of margin to spend in the pit lane.

Undercut and overcut

Undercut: pitting early

You come in one or two laps before the rival you're chasing. You come out on fresh tyres while they're still on worn ones. Those two laps of theirs are slow and yours are quick, so when they stop, you emerge in front.

It works when: the difference between new and worn tyres is big, the pit lane is quick and there's no traffic on your out-lap.

It fails when: new tyres take a lap to come in — which is exactly the lap you needed the time from.

Overcut: staying out

The opposite. You stay out while your rival has already stopped and is struggling with cold tyres and traffic.

It works when: your tyres degrade slowly, the track is improving, or whoever stopped is going to come out in a group.

It fails when: your tyres fall off a cliff. Then every extra lap is time you never get back.

In amateur racing the undercut is the one that works most often, simply because almost nobody is watching what anyone else is doing.

Managing the tyres

A tyre dies in two different ways, and it's worth not confusing them:

• Wear — the rubber goes. Progressive and irreversible.
• Overheating — it goes past temperature and loses grip. Reversible: look after it for two laps and it comes back.

What punishes them, in order:

1. Wheelspin on corner exit. The worst thing you can do to the rear axle.
2. Locking under braking. One flat spot and the stint is over.
3. Sustained sliding in fast corners: it generates enormous heat.
4. Pressures outside the window, especially above it.

How to look after them without losing pace: smoother throttle, one extra click of traction control on the opening laps with a full tank, and don't fight for a place ten laps before your stop. If you feel them going, back off for two laps: recovering temperature costs less than recovering positions with a broken car. The detail is in the tyre pressures article.

The stop, step by step

1. Decide a lap in advance. Improvising is how people miss the pit entry.
2. Prepare the line. Move to the pit side early, without braking hard on anyone's racing line.
3. Limiter before the line. Not as you cross it: before.
4. Brake for your box with margin. Overshooting and having to reverse costs more than arriving slowly.
5. Look before you leave. Cars already in the lane have priority.
6. Cold tyres on the out-lap. Don't attack until they're in, and be careful at the first heavy braking zone.

When it goes wrong

• Safety car. The strategy lottery: pitting under yellow costs far less time. If you're near your window, come in.
• It starts raining. Change brake bias and driver aids first, and decide on tyres by how much pace you're losing, not by how much water you can see.
• Damage. Do the maths: repairs cost seconds, but a car that's two seconds slower for twenty laps costs forty.
• A time penalty. If it's the kind served in the pits, take it with your mandatory stop and you lose far less.
• Short on fuel. Lifting a little on the long straights saves a surprising amount and costs little time. Better that than stopping on the last lap.

And most important: write down what happened. Real consumption, degradation, pit time. After three races you have your own numbers and stop guessing.

Frequently asked