Same car, same setup, same track. Yesterday it was perfect and today it slides everywhere. Nine times out of ten the temperature changed and your tyre pressures are now wrong.
That is all this topic really is. The temperature moves, the tyres move with it, and you bring them back to the window.
This page is part of the ACC setup guide.
Air temperature and track temperature
ACC shows two numbers and they are not the same thing.
| Air temperature | Track temperature | |
|---|---|---|
| Where you set it | In the session weather settings | You do not set it. The game works it out |
| What moves it | Mostly your setting | Air temperature, sun, cloud cover and time of day |
| How fast it moves | Slowly | Quickly. Clouds or sunset can drop it a lot |
| What it does to the car | Cools the tyres, the brakes and the engine | Heats the tread and changes the grip |
| What I use it for | The first guess at cold pressures | Deciding how hard I can push the tyres |
On a sunny afternoon the track is a lot hotter than the air. Under cloud or at night the two come close together. So the same 25 C air can mean a very different track.
What temperature does to the tyres
The tyre has one window: 26.0 to 27.0 psi hot, with the tread at about 80 to 90 C. That window is the same on a cold day and a hot day. What changes is how easy it is to get there.
- Hot track: the tyre heats quickly and goes past the window. Pressure climbs with it. The car feels fine for three laps, then starts to slide, and sliding makes more heat.
- Cold track: the tyre takes longer to warm up and may never reach the window. Pressure stays low, the car feels lazy and the front does not bite.
In real racing it is the same story. Track temperature is one of the first numbers a race engineer looks at in the morning.
The 0.1 psi rule
The rule most ACC drivers use: for every 1 C change in air temperature, change the cold pressures by about 0.1 psi. Hotter air, lower cold pressure. Colder air, higher cold pressure.
Use air temperature for this, not track temperature. The air moves slowly and predictably. The track jumps around with the sun.
It is a first guess and nothing more. Do three laps, read the hot pressures, correct. The full method is in the ACC tyre pressure guide.
What to change for hot and cold
| Condition | What you feel | What I would change |
|---|---|---|
| Cold track | No grip for the first laps, front will not bite, hot pressures under 26 psi | Raise cold pressures, close the brake ducts a step, take two laps to build temperature |
| Hot track | Car slides more as the stint goes on, rears greasy on exit, pressures over 27 psi | Lower cold pressures, open the brake ducts a step, one more click of TC1 |
| Track cooling during the race, for example into the evening | Pressures fall through the stint | Start a little higher. Add pressure at the pit stop |
| Track heating during the race, for example morning into midday | Pressures climb through the stint | Start a little lower. Take pressure out at the pit stop |
| Clouds come over | Grip changes within a few laps | Nothing on the setup. Know that it is coming and adapt |
Brake ducts are the second tool after pressures. Brake heat goes through the wheel into the tyre, so a more open duct means cooler brakes and slightly lower pressures. On a hot day I would open them a step and then set the pressures again. Keep the front brakes around 600 to 650 C.
Do not rebuild the setup for temperature. Pressures and ducts cover most of it. If the car still eats the rear tyres on a hot track, look at the driving first. More on that in the ACC tyre wear guide.
Temperature and lap time
A cooler track is usually faster, as long as the tyres still reach their window. The air is denser too, so the engine makes a little more power and the wings make a little more downforce.
A hot track is slower over a stint. The first lap can be good, but the tyres go over temperature and the times drift.
This matters when you compare yourself with other people. A lap time from a 22 C session and one from a 35 C session are not the same lap. Compare times set in similar conditions.
Races where the temperature moves
In a short race with fixed weather, set the pressures once and forget it.
In a longer race the time of day moves, and the track temperature moves with it. A race that starts at 16:00 and runs into the evening will cool down. Pressures that were perfect at the start will be low an hour later.
So plan for the middle of the stint, not the first lap. And use the pit stop: you can change the pressures of the next set from the MFD before you come in. The steps are in the ACC pit stop guide.
If rain is in the forecast, everything changes again. That is covered in the ACC wet weather guide.
Using a downloaded setup
Every setup was built at one temperature. If you download one and drive it in a session that is 8 C warmer, the pressures are wrong from the first lap, and you will blame the setup.
Before a race, load the setup in a practice session with the same weather as the race. Three laps, check the hot pressures, correct, save it with the temperature in the name. It takes five minutes.
FAQ
What is the best track temperature in ACC?
There is no single number. Mild conditions are the easiest, because the tyres reach 80 to 90 C without overheating. Very hot and very cold tracks both cost lap time.
What is the difference between air and track temperature in ACC?
You set the air temperature in the session settings. The game works out the track temperature from the air, the sun, cloud cover and time of day. In the sun the track is much hotter than the air.
How much should I change tyre pressures for temperature in ACC?
About 0.1 psi of cold pressure for every 1 C of air temperature. Lower when it gets hotter, higher when it gets colder. Then check after three laps.
Why are my tyres overheating in ACC?
A hot track, pressures that are too high, or too much sliding. Lower the cold pressures, open the brake ducts a step and be smoother on the throttle.
Why do I have no grip on a cold track in ACC?
The tyres are under their window. Raise the cold pressures so the hot pressure reaches 26.0 to 27.0 psi, close the brake ducts a step and build up over two laps.
Is a cold track faster in ACC?
Usually, if the tyres still get up to temperature. Cooler air helps the engine and the aero, and the tyres do not overheat.
Does track temperature change during a race in ACC?
Yes, when time moves forward in the session. It follows the time of day and the clouds, so a race into the evening cools down and the pressures drop.