Class Wheel

Represents the physical wheel and tire assembly with all related properties. Contains both the physical characteristics (radius, width, mass) and visual references.

Key components:

  • Physical properties: Define wheel geometry and inertia
  • Visual containers: Separate rotating and non-rotating parts
  • Runtime state: Angular velocity, RPM, rotation angles

The wheel uses realistic physics calculations:

  • Inertia = mass * radius²
  • Angular velocity affects acceleration/braking response
  • Width affects contact patch and ground detection

Note: Call WheelController.Initialize() after changing physical properties.

Inheritance
object
Wheel
Namespace: NWH.WheelController3D
Assembly: NWH.WheelController.dll
Syntax
[Serializable]
public class Wheel

Fields

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INERTIA_COEFFICIENT

Radius-of-gyration coefficient for wheel inertia. Tire+rim mass sits between a solid disc (0.5) and a thin ring (1.0); 0.65 reflects mass biased toward the rim/tread.

Declaration
public const float INERTIA_COEFFICIENT = 0.65
Field Value
Type Description
float
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MASS_DENSITY_COEFFICIENT

Density coefficient for wheel mass calculation. Empirically tuned so that a standard wheel (r=0.35m, w=0.25m) weighs ~30kg.

Declaration
public const float MASS_DENSITY_COEFFICIENT = 980
Field Value
Type Description
float
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angularVelocity

Current angular velocity of the wheel in radians per second [rad/s]. Positive values indicate forward rotation. Related to vehicle speed: linear_speed = angular_velocity * radius. Affected by motor torque, brake torque, and ground friction. High inertia wheels take longer to change angular velocity.

Declaration
[NonSerialized]
[Tooltip("Wheel rotation speed in rad/s. Positive = forward rotation.")]
public float angularVelocity
Field Value
Type Description
float
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autoCalculateMass

When true, mass is auto-calculated from radius and width. When false, mass can be set manually.

Declaration
[SerializeField]
[Tooltip("Automatically calculate mass from wheel dimensions. Disable to set manually.")]
public bool autoCalculateMass
Field Value
Type Description
bool
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axleAngle

Current cumulative rotation angle of the wheel around its axle in degrees. Continuously increases/decreases as wheel rotates (not clamped to 360). Used for visual rotation of the wheel mesh. Reset to 0-360 range periodically to prevent float overflow. Rotation axis is typically the local X-axis of the wheel.

Declaration
[NonSerialized]
[Tooltip("Cumulative wheel rotation angle in degrees. Used for visual rotation.")]
public float axleAngle
Field Value
Type Description
float
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inertia

Rotational inertia of the wheel in kg⋅m² [kilogram meter squared]. Calculated automatically via CalculateInertia(): inertia = INERTIA_COEFFICIENT * mass * radius². Higher inertia:

  • Slower to accelerate/decelerate (more realistic for heavy wheels)
  • Better maintains speed (momentum)
  • May cause wheelspin under hard acceleration Lower inertia:
  • More responsive throttle/brake
  • Better for arcade-style handling Do not modify directly - change mass/radius and call Initialize().
Declaration
[Tooltip("Wheel rotational inertia in kg⋅m². Higher = slower to change speed.")]
[ShowInTelemetry(NaN, NaN, null, null, 1)]
public float inertia
Field Value
Type Description
float
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localAxleRotation

Rotation of the wheel including axle rotation, camber rotation, damage rotation, and any other rotation around the wheel axle. Does not include steer rotation.

Declaration
[NonSerialized]
[Tooltip("Rotation of the wheel including axle rotation, camber rotation, damage rotation, and any other rotation\r\naround the wheel axle. Does not include steer rotation.")]
public Quaternion localAxleRotation
Field Value
Type Description
Quaternion
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mass

Mass of the wheel assembly (rim + tire) in kilograms [kg]. Auto-calculated from radius and width when autoCalculateMass is true. Used to calculate rotational inertia but does NOT affect vehicle weight.

Declaration
[SerializeField]
[Tooltip("Wheel mass in kg. Auto-calculated or manually set.")]
[ShowInTelemetry(NaN, NaN, null, null, 1)]
public float mass
Field Value
Type Description
float
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meshCollider

MeshCollider that handles wheel collisions when suspension can't provide enough force. Automatically generated cylinder mesh covering the wheel. Active when:

  • Vehicle is upside down or on its side
  • Suspension bottoms out (harsh landings)
  • No suspension (wheel directly on collider) Uses zero friction to let WheelController handle all friction calculations. Do not modify or remove - managed automatically by WheelController.
Declaration
[Tooltip("Auto-generated collider for edge cases. Do not modify manually.")]
public MeshCollider meshCollider
Field Value
Type Description
MeshCollider
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nonRotatingContainer

Transform container for parts that move with suspension but don't rotate with the wheel. Parent these objects to this container:

  • Brake calipers
  • Mud guards/fenders (if attached to suspension)
  • Suspension components (control arms, springs)
  • Wheel speed sensors

This container follows suspension movement (up/down) and steering angle, but does not rotate with wheel spin. Automatically created as "NonRotating" child if not assigned.

Declaration
[Tooltip("Container for non-rotating parts like brake calipers. Follows suspension but doesn't spin.")]
public Transform nonRotatingContainer
Field Value
Type Description
Transform
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nonRotatingVisual

!OBSOLETE! - Check the v11 to v12 upgrade notes! Parent the visual to the rotatingContainer instead. Object representing non-rotating part of the wheel. This could be things such as brake calipers, external fenders, etc.

Declaration
[Obsolete]
[Tooltip("!OBSOLETE! - Check the v11 to v12 upgrade notes! Parent the visual to the rotatingContainer instead.Object representing non-rotating part of the wheel. This could be things such as brake calipers, external fenders, etc.")]
public GameObject nonRotatingVisual
Field Value
Type Description
GameObject
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radius

Total radius of the wheel (rim + tire) in meters [m]. Measured from axle center to tire tread surface.

Typical values:

  • Motorcycles: 0.25-0.35m
  • Small cars: 0.28-0.32m
  • Standard cars: 0.30-0.38m
  • SUVs/Trucks: 0.35-0.50m
  • Monster trucks: 0.60-1.00m

Affects:

  • Vehicle speed (larger = higher speed at same RPM)
  • Torque at ground (larger = less torque multiplication)
  • Ground clearance and suspension geometry

Call WheelController.Initialize() after changing!

Declaration
[Min(0.001)]
[ShowInTelemetry(NaN, NaN, null, null, 1)]
[Tooltip("Wheel radius in meters. Affects speed, torque, and clearance. Call Initialize() after changing!")]
public float radius
Field Value
Type Description
float
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rimOffset

Lateral offset of the wheel rim from the suspension pivot point in meters [m]. Also known as wheel offset or ET (Einpresstiefe).

Effects:

  • Positive: Wheel moves outward (wider track)
  • Negative: Wheel moves inward (narrower track)
  • Changes scrub radius and steering feel
  • Affects suspension geometry and roll center

Typical values:

  • Standard cars: 0.03-0.06m
  • Wide body/stance: 0.08-0.15m
  • Trucks (dual wheels): 0.15-0.25m

Used for steering pivot calculation.

Declaration
[Tooltip("Wheel lateral offset in meters. Positive = outward. Affects steering geometry.")]
public float rimOffset
Field Value
Type Description
float
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rotatingContainer

Transform container for all parts that rotate with the wheel. Parent these objects to this container:

  • Wheel mesh (rim and tire)
  • Brake discs/rotors
  • Wheel bolts/nuts (visual)
  • Hubcaps or center caps

This container handles:

  • Wheel spin rotation (rolling)
  • Suspension movement (up/down)
  • Steering angle
  • Camber angle

Automatically created as "Rotating" child if not assigned. First child should be the main wheel mesh for auto-sizing.

Declaration
[Tooltip("Container for rotating parts like wheel mesh and brake discs. Spins with wheel.")]
public Transform rotatingContainer
Field Value
Type Description
Transform
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rpm

Current wheel rotation speed in revolutions per minute [RPM]. Calculated from angular velocity: RPM = angularVelocity * 9.55. Positive values indicate forward rotation.

Useful for:

  • Dashboard/HUD displays
  • Gear shift calculations
  • Sound system (tire noise pitch)
  • Visual effects (motion blur intensity)

Relationship to speed: vehicle_speed ≈ (RPM / 60) * 2π * radius

Declaration
[ShowInTelemetry(0, 100, "0", "RPM", 1)]
[Tooltip("Wheel rotation speed in RPM. Positive = forward.")]
public float rpm
Field Value
Type Description
float
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visual

!OBSOLETE! - Check the v11 to v12 upgrade notes! Parent the visual(s) to the rotatingContainer instead. GameObject representing the visual aspect of the wheel / wheel mesh. Should not have any physics colliders attached to it.

Declaration
[Obsolete]
[Tooltip("!OBSOLETE! - Check the v11 to v12 upgrade notes! Parent the visual(s) to the rotatingContainer instead.GameObject representing the visual aspect of the wheel / wheel mesh.\r\nShould not have any physics colliders attached to it.")]
public GameObject visual
Field Value
Type Description
GameObject
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width

Width of the tire tread in meters [m]. Affects ground detection area and visual appearance.

Typical values:

  • Motorcycles: 0.08-0.20m
  • Small cars: 0.155-0.195m (155-195mm tires)
  • Standard cars: 0.195-0.255m (195-255mm tires)
  • Sports cars: 0.225-0.335m (225-335mm tires)
  • SUVs/Trucks: 0.235-0.355m (235-355mm tires)

Effects:

  • Wider = larger contact patch, potentially more grip
  • Wider = better stability but more rolling resistance
  • Ground detection samples across entire width

Call WheelController.Initialize() after changing!

Declaration
[Min(0.001)]
[Tooltip("Tire width in meters. Affects contact patch. Call Initialize() after changing!")]
public float width
Field Value
Type Description
float

Methods

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CalculateInertia()

Calculates wheel rotational inertia from mass and radius. Formula: inertia = INERTIA_COEFFICIENT * mass * radius²

Declaration
public float CalculateInertia()
Returns
Type Description
float
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CalculateMass()

Calculates expected wheel mass from radius and width. Formula: mass = MASS_DENSITY_COEFFICIENT * radius² * width

Declaration
public float CalculateMass()
Returns
Type Description
float