Tyre Pressures in Assetto Corsa

Why pressure is the #1 parameter

Before springs, before alignment, before aero: tyre pressure. It's the setup parameter with the biggest impact on grip, and the one with the fastest feedback loop. If you get it wrong, no other adjustment will fully compensate.

The reason is simple: the tyre is the only part of the car that touches the road. Its effective contact patch — the actual rubber pressed into the asphalt at any given moment — changes dramatically with pressure. Too much pressure and the tyre balloons, riding only on the centre. Too little and the centre collapses, riding only on the shoulders. At both extremes you lose contact area, and grip with it.

In Assetto Corsa, the tyre model simulates this physics accurately. That means bad pressure doesn't just cost you lap time: it changes how the car behaves. A car on low pressures feels "doughy"; one on high pressures feels "nervous" and loses traction under throttle. Learning to recognize those feelings is the first step in understanding what's wrong.

Cold pressure vs hot pressure

This is the first source of confusion for a lot of people. In Assetto Corsa's setup menu, you can only edit the cold pressure: what the tyre reads before rolling, with the car stationary. The pressure that actually matters is the hot pressure: what the tyre reaches after 2-3 laps of running.

As the tyre rolls, lateral loads and asphalt friction heat it up. The air (or nitrogen, doesn't matter at this level) inside expands and pressure rises. How much it rises depends on compound, ambient temperature, track and driving style. As a reasonable reference:

Practical rule: if you want 27 PSI hot and your compound is a GT slick that gains 4 PSI on the run, your starting cold pressure should be 23 PSI. Those are the numbers you type into the setup menu.

The optimal window by tyre type

Every compound has a hot pressure band where the car gives its best performance. Below that band the tyre overheats and degrades fast; above it, you lose contact patch. These are the typical windows in Assetto Corsa:

• GT3 / GT4 slicks — 26 to 28 PSI hot. They gain about 4 PSI, so you start cold at 22-24 PSI.
• LMP / Prototype slicks — 24 to 27 PSI hot. Some cars want even lower values.
• Semi-slick (Trofeo, Hankook semi) — 28 to 30 PSI hot.
• Street tyres (BMW M3 street, Lotus Evora street) — 30 to 33 PSI hot. Climb less while running.
• Vintage (Trofeo Classico, etc.) — varies a lot, check each car. Usually 26-30 PSI.
• Wet — 28 to 32 PSI hot. They don't climb much because water cools them.

These numbers are approximate. The exact window varies with the specific car (a Ferrari 488 GT3 isn't a clone of an Audi R8 LMS), the mod (heavy mods like URD or RSS can have their own windows), and which version of Assetto Corsa you're running (vanilla AC vs ACC use different tyre models).

That's why what comes next matters more than these theoretical numbers: learning to read temperatures so you know where you are, with your car, on your circuit.

How to read temperatures to diagnose

In Assetto Corsa, each tyre has three temperature sensors: inner (the side facing the car), middle, and outer. Those three readings tell you whether your pressure is correct — more reliably than any generic advice.

Enable the in-sim tyre app (Apps → Tyre app) or use an external tool like Content Manager. After 3 hot laps, look at the three temperatures on each wheel and compare them:

Temperature distribution lets you separate two diagnoses that get confused: pressure problem vs camber problem. Pressure drives the middle vs edges curve. Camber drives the inner vs outer asymmetry. If you start increasing camber without first fixing pressure, you're shooting in the dark.

Write down the values before and after each change. Five minutes of notes save you five hours of guessing.

Step-by-step adjustment process

This is the clean flow that gets you to an optimized pressure without wasting time. Works for any car, any track.

1. Leave the pit with the default setup and do 1 lap at medium pace to warm up.
2. Run 2-3 laps at race pace. Not qualifying laps — laps that represent how you'll actually drive.
3. Return to the pit without hard braking. If you brake hard coming in, rear pressures spike and ruin the reading.
4. Write down pressure and temperature for all 4 wheels, all 3 zones each. Pause the game if needed.
5. Compare to the optimal window from the previous section. High pressure: drop cold pressure. Low pressure: raise it.
6. Change one wheel at a time, in 1 PSI steps. Run another 3 laps. Repeat.
7. Once all four are in their window, lock that setup as your base. That's your starting point for everything else (springs, alignment, etc.).

The most common mental error is trying to "fine-tune" pressure to the tenth of a PSI on the first attempt. It doesn't work. Small steps get lost in the noise of your driving. Better to make 1 PSI changes, see the direction, and close the gap from there.

Five common mistakes

I've seen these on Discord replays and streams from people asking why their car is slow. If you're doing any of them, drop everything and fix it before touching anything else.

1. Copying pressures from a YouTube setup without context. Pressure depends on your ambient temperature, your track, your compound and your driving. Someone else's pressures aren't yours.
2. Adjusting in any session without thinking about temperature. A session at 35°C and one at 18°C need different cold pressures to hit the same hot target. If you're racing at a specific time, practice at that temperature.
3. Looking only at pressures, not temperatures. Pressure alone doesn't tell you if you're right — only the temperature distribution confirms it.
4. Changing pressure and something else in the same iteration. If you touch pressure and camber together, you won't know which one improved the car. One thing per iteration.
5. Assuming the default setup is wrong before checking temperatures. Many defaults sit reasonably close to the window. If your temps look even, leave pressure alone and find time elsewhere.

How conditions affect pressure

Optimal pressures aren't fixed: they shift with track conditions. These are the three factors that move the needle the most in Assetto Corsa.

Ambient temperature

The hotter it gets, the more the tyre heats up while running and the more pressure builds. For every 10°C of track temperature increase, hot pressure climbs between 0.5 and 1 PSI off the same cold pressure. Going from a 20°C session to a 35°C one means dropping cold pressure by about 1 PSI to keep the same hot target.

Track type

A circuit with lots of fast corners (Spa, Silverstone) puts the tyre under sustained lateral loads and heats it more. A stop-and-go track (Hungaroring, Brands Hatch Indy) generates more shoulder heat but less overall. In practice, the same car often wants 0.5-1 PSI less cold pressure on a high-load track than on a technical one.

Rain

In rain you run wets, which have their own window (28-32 PSI), and water cools the tyre so pressure doesn't climb much. The trap: if you start dry and rain comes mid-race, slicks lose temperature fast and pressure drops, killing grip faster than you'd expect. That's why in sessions with rain risk some drivers start with cold pressures 0.5 PSI above normal as a margin.

Frequently asked questions