Tyre pressure is the first thing I would check in any ACC setup, before wing, before bars, before anything. The tyre has a narrow window where it grips. Miss it by one psi and you have thrown away more time than the rest of the setup can give back.
Here is the window, how to hit it, and what moves it.
The best tyre pressures in ACC
| Tyre | Hot pressure target | Where I would aim |
|---|---|---|
| Dry slick, GT3 and GT4 | 26.0 to 27.0 psi | The middle, about 26.5, so a hot stint does not push you out of the top |
| Wet tyre | 30.0 to 31.0 psi | The middle, about 30.5 |
These are hot pressures. Not the number you type in the setup. The number you see on the tyre widget after four or five clean laps.
That is the whole secret. Everything below is how to land in that window and stay in it.
Cold pressure against hot pressure
The setup screen asks for a cold pressure. That is what the tyre has when it leaves the garage. As you drive, the tyre heats up, the air inside expands and the pressure climbs. A few laps in, it settles. That settled number is the hot pressure, and that is the one that has to be in the window.
How much it climbs depends on the car, the track, the weather and you. So nobody can give you a cold pressure that always works. A setup you downloaded was right for the day its author drove it. On your day it is a starting point.
How to set tyre pressures in ACC
1. Match the weather
In a practice session, set the air temperature, the cloud cover and the time of day to what the race will have. Pressures set at 18°C mean nothing for a race at 32°C.
2. Race fuel, five clean laps
Put in race fuel and drive at race pace. No cruising, no hero laps. If you spin or go off, the tyres pick up dirt and lose heat, so add a lap.
3. Pit and read the hot pressures
Come back to the garage and open the setup screen. The Tyres tab shows the hot pressure of each tyre from your run. You can also read them live on the tyre widget while you drive. How to read that widget is in the ACC HUD guide.
4. Work out the gap
Pick a target in the middle of the window. I would use 26.5 in the dry. For each tyre, take the hot pressure and subtract the target.
5. Move the cold pressure by the same amount
A change in cold pressure gives close to the same change in hot pressure. Not exactly, but close enough to get you there in two tries.
Here is an example on a clockwise track, where the left side does more work.
| Tyre | Cold in setup | Hot after 5 laps | Gap to 26.5 | New cold |
|---|---|---|---|---|
| Front left | 25.0 | 27.4 | 0.9 too high | 24.1 |
| Front right | 25.0 | 26.9 | 0.4 too high | 24.6 |
| Rear left | 24.8 | 26.6 | 0.1 too high | 24.7 |
| Rear right | 24.8 | 26.1 | 0.4 too low | 25.2 |
Notice all four numbers end up different. That is normal. The outside tyres in the long corners run hotter and need a lower cold pressure. Copying one number to all four tyres is the most common mistake I see.
6. Confirm
Five more laps. If every tyre is between 26.0 and 27.0, save the setup with the temperature in the name, something like spa_race_24C. Next time you race there in similar weather, you start one step ahead.
Why the window matters
Pressure decides the shape of the contact patch, the part of the tyre that touches the road.
- Too low: the tyre is soft and moves around on the rim. The car feels lazy and vague, the shoulders overheat, and the tyre wears faster.
- Too high: the tyre balloons and runs on the middle of the tread. Less rubber on the road, less grip, and the car skates.
Inside the window the patch is flat and the tyre does what the car asks. You feel it straight away in the braking zone and on turn in.
Tyre temperature
Pressure and temperature go together. The setup screen and the widget show both.
| Tyre core temperature | What it means |
|---|---|
| Under 70°C | Too cold. The surface grains and the car slides |
| 70 to 80°C | Working, not at its best yet |
| 80 to 90°C | The sweet spot |
| 90 to 100°C | Still working, wearing faster |
| Over 100°C | Too hot. The tyre blisters |
If the pressures are in the window and the temperatures are still wrong, pressure is not your problem. Look at camber, at the brake ducts, and at how much you are sliding the car. Sliding is what cooks a tyre. What that does over a stint is in the ACC tyre wear guide.
What moves your pressures
| What changed | What the hot pressure does | What to do with the cold pressure |
|---|---|---|
| Air and track get hotter | Goes up | Lower it |
| Air and track get colder | Goes down | Raise it |
| Night falls in a long race | Goes down | Raise it at the next stop |
| More fuel on board | Goes up a little | Check on race fuel, not qualifying fuel |
| Brake ducts closed a step | Goes up | Lower it a touch, mostly at the front |
| You push harder or slide more | Goes up | Set pressures at race pace, not on a cruise |
| Track goes from dry to damp on slicks | Goes down fast | Raise it, or pit for wets |
A rule of thumb that gets you close: about 0.1 psi for every 1°C of air temperature. If the air is 5°C warmer than the day you built the setup, start with the cold pressures about 0.5 psi lower, then check. It is a starting point, not a law. The track surface matters as much as the air, and I go through that in the ACC track temperature guide.
Pressures for the pit stop
The pressures in your setup are for the first set of tyres. For the next set, you choose the pressures in the pit strategy, either in the setup before the race or on the pit page of the MFD while you drive.
Two things catch people out:
- The game does not adjust for you. If the race started at 3 pm and you stop at 7 pm, the track is colder. The pressures that worked at the start will come out low. Raise them on the MFD before you come in.
- A new set starts cold. For the first two laps after a stop the pressures are low and the grip is not there. Do not judge them on the out lap.
How to drive the stop itself is in the ACC pit stop guide.
Wet tyre pressures
The wet tyre wants 30.0 to 31.0 psi hot. That is a lot higher than the slick, and it is on purpose. A harder tyre keeps its tread blocks open and cuts through the water.
Rain cools everything, so the tyre gains less pressure from cold to hot than it does in the dry. The cold pressure you set is closer to the hot pressure you get. Use the same method: five laps, read, adjust.
On a drying track the wets overheat fast and the pressures shoot up. If the line is dry, you should already be on your way in for slicks. The driving side and the rest of the rain setup are in the ACC wet weather guide.
Qualifying pressures
A qualifying run is short. One out lap, two push laps. The tyres do not have time to reach the pressure they would have on lap ten.
So for qualifying I would start with cold pressures a little higher than the race setup, so the tyre is in the window on the first push lap instead of the fifth. Run the same test, but read the pressures after lap two, not lap five. Keep it as a separate setup file.
Mistakes I see
- Reading the pressures on the out lap. They are still climbing.
- Same cold pressure on all four tyres. Each corner of the car works differently.
- Setting pressures on low fuel for a race. The heavier car puts more heat in the tyres.
- Never checking again. New day, new temperature, new pressures.
- Chasing the balance with pressures. Get them in the window and leave them. Fix the balance with the anti roll bars and the wing, which I cover in the ACC setup guide.
FAQ
What is the best tyre pressure in ACC?
26.0 to 27.0 psi hot for dry tyres on GT3 and GT4 cars, and 30.0 to 31.0 psi hot for wet tyres. Hot means measured after four or five clean laps at race pace.
What cold tyre pressure should I set in ACC?
There is no fixed number, because it depends on the car, the track and the temperature. Set a starting value, drive five laps, and move each cold pressure by the gap between the hot reading and your target.
Where do I see hot tyre pressures in ACC?
On the tyre widget in the HUD while you drive, and on the Tyres tab of the setup screen when you return to the garage after a run.
Why are my left and right tyre pressures different?
The side of the car on the outside of the long corners does more work and gets hotter, so it gains more pressure. Give each tyre its own cold pressure so all four land in the window.
How much does temperature change tyre pressure in ACC?
As a rule of thumb, about 0.1 psi for every 1°C of air temperature. Hotter air means higher hot pressures, so lower the cold pressure. Always confirm with a five lap run.
What tyre pressure should I use in the wet in ACC?
Aim for 30.0 to 31.0 psi hot on the wet tyre. The tyre gains less pressure in the rain, so the cold value sits closer to the target than it does in the dry.
Can I change tyre pressures during a race in ACC?
Yes, for the next set. Open the pit page on the MFD and change the pressures before you stop. You cannot change the pressure of the tyres that are on the car.