Documentation

Learn how to use TreCorsa's track editor

Road Grip & Settings

Road Grip & Settings (surfaces.ini)

TreCorsa allows you to configure road grip and physics properties using Assetto Corsa's surfaces.ini system. You can assign different surface types to roads (like wet asphalt, high-grip surfaces, or custom surfaces) and create custom surface definitions that affect how cars handle on different parts of your track.

What is surfaces.ini?

surfaces.ini is an Assetto Corsa configuration file that defines surface physics properties. It controls how tires interact with different road surfaces, affecting grip, damping, force feedback, and other driving characteristics. When you export a track from TreCorsa, custom surface definitions are automatically included in the surfaces.ini file.

Standard Assetto Corsa surfaces (ROAD, GRASS, KERB, SAND) are already defined in AC's system files, so TreCorsa only exports custom surfaces you create. If you don't create any custom surfaces, the exported surfaces.ini will be empty and AC will use its default surface properties.

Assigning Surfaces to Roads

To assign a surface type to a road:

  1. Open the Layers Panel if it's not expanded.
  2. Find the road you want to configure in the Roads tab
  3. Click the settings button (⚙️) next to the road name
  4. The Road Surface Settings popup will appear
  5. Select a surface type from the dropdown menu
  6. Click Apply to save the changes

Click the Open manager button to create custom surfaces.

The surface assignment applies immediately to the road mesh. You can assign different surfaces to different roads, allowing you to create varied track conditions.

Surface Manager

The Surface Manager allows you to create, edit, and delete custom surface definitions. To open it:

  • Click the "Open Manager" button in the Road Surface Settings popup, or

In the Surface Manager, you can:

  • Create new surfaces - Click "+ New Surface" to create a custom surface definition
  • Edit existing surfaces - Click "Edit" on any surface card to modify its properties
  • Delete surfaces - Click "Delete" to remove custom surfaces (default surfaces cannot be deleted)
  • Filter by type - Use the filter dropdown to show only specific surface types (Road, Slab, Kerb, Grass, Sand)

All surfaces you create are saved to your account and can be used across all your tracks.

Surface Types

TreCorsa supports several surface types:

  • Road - Standard road surfaces.
  • Slab - Concrete slab surfaces
  • Kerb - Kerb/curb surfaces
  • Grass - Grass surfaces
  • Sand - Sand surfaces

When creating a road surface, the KEY name will automatically start with "ROAD" - you can add a suffix like "SIDE" or "DUSTY" to create variations (e.g., ROADSIDE, ROADDUSTY).

Surface Properties

Each surface can have various physics properties that affect driving behavior:

  • Friction (0-2) - Tire grip multiplier. 1.0 = perfect grip, higher values = more grip, lower values = less grip. Most Kunos tracks use values around 0.9-0.95 for realistic road surfaces. This is the most important property for controlling how cars handle on the surface.
  • Damping (0-1) - Surface damping effect. Controls how much the surface absorbs energy from the car.
  • Valid Track (toggle) - Whether cars stay on track when driving on this surface. If disabled, cars will be flagged as off-track when on this surface.
  • Is Pitlane (toggle) - Marks the surface as part of the pitlane. Useful for pit speed limits and other pitlane-specific behaviors.
  • Dirt Additive (0-1) - How much dirt accumulates on tires when driving on this surface. Higher values cause tires to get dirtier faster.
  • Black Flag Time (0-10 seconds) - Time before a black flag is shown when off-track on this surface. Only applies if Valid Track is disabled.
  • FF Effect - Force feedback effect type (NULL, 0, or 1). Set to 1 if you want to use Vibration Gain and Vibration Length settings. Mostly only used for grass, sand, and kerbs.
  • Vibration Gain (0-2) - Force feedback vibration intensity. Controls how much vibration is felt through the steering wheel. Requires FF Effect to be set to 1.
  • Vibration Length (0-5 meters) - Vibration wavelength. Controls the frequency/spacing of vibrations. Requires FF Effect to be set to 1.
  • Sin Height (0-0.1 meters) - Surface wave height. Creates subtle surface undulations.
  • Sin Length (0-2 meters) - Surface wave length. Controls the spacing of surface waves.
  • Sound File - WAV file name for surface sound effects (e.g., grass.wav). Plays when driving on this surface.
  • WAV Pitch (0-5) - Sound pitch multiplier for the surface sound effect.

Creating Custom Surfaces

To create a custom surface:

  1. Open the Surface Manager
  2. Click "+ New Surface"
  3. Enter a Name for your surface (e.g., "Wet Asphalt", "High Grip")
  4. Select a Surface Type (Road, Slab, Kerb, Grass, or Sand)
  5. Set the Key Name:
    • For road surfaces: The key must start with "ROAD". You can add a suffix like "WET" or "GRIP" (e.g., ROADWET, ROADGRIP)
    • For other types: Enter the key name directly (e.g., GRASS, KERB, SAND)
  6. Adjust the Surface Properties using the sliders and toggles
  7. Click "Create Surface" to save

Once created, your custom surface will appear in the Road Surface Settings dropdown and can be assigned to any road.

Default Surfaces

TreCorsa includes default surface definitions that are always available:

  • Default Road - Standard road surface with normal grip (friction = 1.0). This is automatically assigned to roads if no other surface is selected.

Default surfaces cannot be edited or deleted, but you can create custom surfaces based on them by adjusting the properties.

How It Works in Export

When you export your track:

  • TreCorsa automatically generates a surfaces.ini file containing all custom surface definitions you've created
  • Standard AC surfaces (ROAD, GRASS, KERB, SAND) are not included - they're already in AC's system files
  • Road meshes are named to match the surface KEY (e.g., "1ROADWET_0" matches a surface with KEY=ROADWET)
  • The surfaces.ini file is included in the track's data folder and automatically loaded by Assetto Corsa

If you haven't created any custom surfaces, the exported surfaces.ini will be empty and AC will use its default surface properties for all roads.

Best Practices

  • Test in Assetto Corsa - Surface properties can significantly affect driving feel. Test your track in AC to ensure the grip feels right
  • Friction is key - The friction value is the most important property. Start with small adjustments (0.05-0.1) and test
  • Name surfaces clearly - Use descriptive names like "Wet Asphalt" or "High Grip" so you can easily identify them later
  • Reuse surfaces - Once created, surfaces can be used across multiple roads and tracks, so create a library of useful surfaces
  • Valid Track setting - Be careful with the "Valid Track" setting. Disabling it will cause cars to be flagged as off-track, which may not be desired for all surfaces