Multiple cars in game

#1 Make sure you're setting the correct tire/springs for each cars datablock in that datablock's onAdd.

#2 When I open the editor only one car is showing, and I put the car in the game it has no wheels
i get this error here:
setWheelTire: datablock does not exist (or is not a tire)
setWheelSpring: datablock does not exist (or is not a spring)
setWheelTire: datablock does not exist (or is not a tire)
setWheelSpring: datablock does not exist (or is not a spring)
setWheelTire: datablock does not exist (or is not a tire)
setWheelSpring: datablock does not exist (or is not a spring)
setWheelTire: datablock does not exist (or is not a tire)
setWheelSpring: datablock does not exist (or is not a spring)

//----------------------------------------------------------------------------

datablock WheeledVehicleTire(CarTire)
{
   // Tires act as springs and generate lateral and longitudinal
   // forces to move the vehicle. These distortion/spring forces
   // are what convert wheel angular velocity into forces that
   // act on the rigid body.
   shapeFile = "~/data/shapes/car/wheel.dts";
   staticFriction = 4.2;
   kineticFriction = 3.15;
   
   
   

   // Spring that generates lateral tire forces
   lateralForce = 18000;
   lateralDamping = 6000;
   lateralRelaxation = 1;

   // Spring that generates longitudinal tire forces
   longitudinalForce = 18000;
   longitudinalDamping = 4000;
   longitudinalRelaxation = 1;
};

datablock WheeledVehicleSpring(CarSpring)
{
   // Wheel suspension properties
   length = 0.85;             // Suspension travel
   force = 3500;              // Spring force
   damping = 3600;             // Spring damping
   antiSwayForce = 3;         // Lateral anti-sway force
};

datablock WheeledVehicleData(Car)
{
   category = "Vehicles";
   shapeFile = "~/data/shapes/car/car.dts";
   emap = true;
   
   mountPose[0] = sitting;

   maxDamage = 1.0;
   destroyedLevel = 0.5;

   maxSteeringAngle = 0.385;  // Maximum steering angle, should match animation
   tireEmitter = TireEmitter; // All the tires use the same dust emitter

   // 3rd person camera settings
   cameraRoll = true;         // Roll the camera with the vehicle
   cameraMaxDist = 4.8;         // Far distance from vehicle
   cameraOffset = 1.5;        // Vertical offset from camera mount point
   cameraLag = 0.26;           // Velocity lag of camera
   cameraDecay = 1.25;        // Decay per sec. rate of velocity lag

   // Rigid Body
   mass = 380;
   massCenter = "0 -0.2 0";    // Center of mass for rigid body
   massBox = "0 0 0";         // Size of box used for moment of inertia,
                              // if zero it defaults to object bounding box
   drag = 0.6;                // Drag coefficient
   bodyFriction = 0.6;
   bodyRestitution = 0.4;
   minImpactSpeed = 5;        // Impacts over this invoke the script callback
   softImpactSpeed = 5;       // Play SoftImpact Sound
   hardImpactSpeed = 15;      // Play HardImpact Sound
   integration = 8;           // Physics integration: TickSec/Rate
   collisionTol = 0.1;        // Collision distance tolerance
   contactTol = 0.1;          // Contact velocity tolerance

   // Engine
   engineTorque = 3300;       // Engine power
   engineBrake = 600;         // Braking when throttle is 0
   brakeTorque = 8000;        // When brakes are applied
   maxWheelSpeed = 50;        // Engine scale by current speed / max speed

   // Energy
   maxEnergy = 100;
   jetForce = 3000;
   minJetEnergy = 30;
   jetEnergyDrain = 2;

   // Sounds
//   jetSound = ScoutThrustSound;
//   engineSound = BuggyEngineSound;
//   squealSound = ScoutSquealSound;
//   softImpactSound = SoftImpactSound;
//   hardImpactSound = HardImpactSound;
//   wheelImpactSound = WheelImpactSound;

//   explosion = VehicleExplosion;
};



//----------------------------------------------------------------------------

datablock WheeledVehicleTire(fordCoupe : CarTire)
{
   // Tires act as springs and generate lateral and longitudinal
   // forces to move the vehicle. These distortion/spring forces
   // are what convert wheel angular velocity into forces that
   // act on the rigid body.
   shapeFile = "~/data/shapes/fordCoupe/wheel.dts";
   staticFriction = 4.2;
   kineticFriction = 3.15;

   // Spring that generates lateral tire forces
   lateralForce = 18000;
   lateralDamping = 6000;
   lateralRelaxation = 1;

   // Spring that generates longitudinal tire forces
   longitudinalForce = 18000;
   longitudinalDamping = 4000;
   longitudinalRelaxation = 1;
};

datablock WheeledVehicleSpring(fordCoupe : CarSpring)
{
   // Wheel suspension properties
   length = 0.85;             // Suspension travel
   force = 2800;              // Spring force
   damping = 3600;             // Spring damping
   antiSwayForce = 3;         // Lateral anti-sway force
};

datablock WheeledVehicleData(fordCoupe : car)
{
   category = "Vehicles";
   shapeFile = "~/data/shapes/fordCoupe/car.dts";
   emap = true;
   
   mountPose[0] = sitting;

   maxDamage = 1.0;
   destroyedLevel = 0.5;

   maxSteeringAngle = 0.385;  // Maximum steering angle, should match animation
   tireEmitter = TireEmitter; // All the tires use the same dust emitter

   // 3rd person camera settings
   cameraRoll = true;         // Roll the camera with the vehicle
   cameraMaxDist = 4.8;         // Far distance from vehicle
   cameraOffset = 1.5;        // Vertical offset from camera mount point
   cameraLag = 0.26;           // Velocity lag of camera
   cameraDecay = 1.25;        // Decay per sec. rate of velocity lag

   // Rigid Body
   mass = 380;
   massCenter = "0 -0.2 0";    // Center of mass for rigid body
   massBox = "0 0 0";         // Size of box used for moment of inertia,
                              // if zero it defaults to object bounding box
   drag = 0.6;                // Drag coefficient
   bodyFriction = 0.6;
   bodyRestitution = 0.4;
   minImpactSpeed = 5;        // Impacts over this invoke the script callback
   softImpactSpeed = 5;       // Play SoftImpact Sound
   hardImpactSpeed = 15;      // Play HardImpact Sound
   integration = 8;           // Physics integration: TickSec/Rate
   collisionTol = 0.1;        // Collision distance tolerance
   contactTol = 0.1;          // Contact velocity tolerance

   // Engine
   engineTorque = 3300;       // Engine power
   engineBrake = 600;         // Braking when throttle is 0
   brakeTorque = 8000;        // When brakes are applied
   maxWheelSpeed = 50;        // Engine scale by current speed / max speed

   // Energy
   maxEnergy = 100;
   jetForce = 3000;
   minJetEnergy = 30;
   jetEnergyDrain = 2;

   // Sounds
//   jetSound = ScoutThrustSound;
//   engineSound = BuggyEngineSound;
//   squealSound = ScoutSquealSound;
//   softImpactSound = SoftImpactSound;
//   hardImpactSound = HardImpactSound;
//   wheelImpactSound = WheelImpactSound;

//   explosion = VehicleExplosion;
};

//-----------------------------------------------------------------------------

function WheeledVehicleData::create(%block)
{
   %obj = new WheeledVehicle() {
      dataBlock = %block;
   };
   return(%obj);
}

//-----------------------------------------------------------------------------

function WheeledVehicleData::onAdd(%this,%obj)
{
   // Setup the car with some defaults tires & springs
   for (%i = %obj.getWheelCount() - 1; %i >= 0; %i--) {
      %obj.setWheelTire(%i,%this.CarTire);
      %obj.setWheelSpring(%i,%this.CarSpring);
      %obj.setWheelPowered(%i,false);
   }
   
   // Steer front tires
   %obj.setWheelSteering(0,1);
   %obj.setWheelSteering(1,1);

   // Only power the two rear wheels...
   %obj.setWheelPowered(2,true);
   %obj.setWheelPowered(3,true);
}

function WheeledVehicleData::onCollision(%this,%obj,%col,%vec,%speed)
{
   // Collision with other objects, including items
   
   
}

#3 Well this works,

datablock WheeledVehicleTire(CarTire)
{
   // Tires act as springs and generate lateral and longitudinal
   // forces to move the vehicle. These distortion/spring forces
   // are what convert wheel angular velocity into forces that
   // act on the rigid body.
   shapeFile = "~/data/shapes/car/wheel.dts";
      
   staticFriction = 4.2;
   kineticFriction = 3.15;
   
   
   

   // Spring that generates lateral tire forces
   lateralForce = 18000;
   lateralDamping = 6000;
   lateralRelaxation = 1;

   // Spring that generates longitudinal tire forces
   longitudinalForce = 18000;
   longitudinalDamping = 4000;
   longitudinalRelaxation = 1;
};

datablock WheeledVehicleSpring(CarSpring)
{
   // Wheel suspension properties
   length = 0.85;             // Suspension travel
   force = 3500;              // Spring force
   damping = 3600;             // Spring damping
   antiSwayForce = 3;         // Lateral anti-sway force
};

datablock WheeledVehicleData(Car)
{
   category = "Vehicles";
   shapeFile = "~/data/shapes/car/car.dts";
   carTire = "CarTire";
   carSpring = "CarSpring";
   
   emap = true;
   
   mountPose[0] = sitting;

   maxDamage = 1.0;
   destroyedLevel = 0.5;

   maxSteeringAngle = 0.385;  // Maximum steering angle, should match animation
   tireEmitter = TireEmitter; // All the tires use the same dust emitter

   // 3rd person camera settings
   cameraRoll = true;         // Roll the camera with the vehicle
   cameraMaxDist = 4.8;         // Far distance from vehicle
   cameraOffset = 1.5;        // Vertical offset from camera mount point
   cameraLag = 0.26;           // Velocity lag of camera
   cameraDecay = 1.25;        // Decay per sec. rate of velocity lag

   // Rigid Body
   mass = 380;
   massCenter = "0 -0.2 0";    // Center of mass for rigid body
   massBox = "0 0 0";         // Size of box used for moment of inertia,
                              // if zero it defaults to object bounding box
   drag = 0.6;                // Drag coefficient
   bodyFriction = 0.6;
   bodyRestitution = 0.4;
   minImpactSpeed = 5;        // Impacts over this invoke the script callback
   softImpactSpeed = 5;       // Play SoftImpact Sound
   hardImpactSpeed = 15;      // Play HardImpact Sound
   integration = 8;           // Physics integration: TickSec/Rate
   collisionTol = 0.1;        // Collision distance tolerance
   contactTol = 0.1;          // Contact velocity tolerance

   // Engine
   engineTorque = 3300;       // Engine power
   engineBrake = 600;         // Braking when throttle is 0
   brakeTorque = 8000;        // When brakes are applied
   maxWheelSpeed = 50;        // Engine scale by current speed / max speed

   // Energy
   maxEnergy = 100;
   jetForce = 3000;
   minJetEnergy = 30;
   jetEnergyDrain = 2;

   // Sounds
//   jetSound = ScoutThrustSound;
//   engineSound = BuggyEngineSound;
//   squealSound = ScoutSquealSound;
//   softImpactSound = SoftImpactSound;
//   hardImpactSound = HardImpactSound;
//   wheelImpactSound = WheelImpactSound;

//   explosion = VehicleExplosion;
};



//----------------------------------------------------------------------------

datablock WheeledVehicleTire(fordCoupeCarTire)
{
   // Tires act as springs and generate lateral and longitudinal
   // forces to move the vehicle. These distortion/spring forces
   // are what convert wheel angular velocity into forces that
   // act on the rigid body.
   shapeFile = "~/data/shapes/fordCoupe/wheel.dts";
   staticFriction = 4.2;
   kineticFriction = 3.15;

   // Spring that generates lateral tire forces
   lateralForce = 18000;
   lateralDamping = 6000;
   lateralRelaxation = 1;

   // Spring that generates longitudinal tire forces
   longitudinalForce = 18000;
   longitudinalDamping = 4000;
   longitudinalRelaxation = 1;
};

datablock WheeledVehicleSpring(fordCoupeCarSpring)
{
   // Wheel suspension properties
   length = 0.85;             // Suspension travel
   force = 2800;              // Spring force
   damping = 3600;             // Spring damping
   antiSwayForce = 3;         // Lateral anti-sway force
};

datablock WheeledVehicleData(fordCoupe)
{
   category = "Vehicles";
   shapeFile = "~/data/shapes/fordCoupe/car.dts";
   carTire = "fordCoupeCarTire";
   carSpring = "fordCoupeCarSpring";
   
   emap = true;
   
   mountPose[0] = sitting;

   maxDamage = 1.0;
   destroyedLevel = 0.5;

   maxSteeringAngle = 0.385;  // Maximum steering angle, should match animation
   tireEmitter = TireEmitter; // All the tires use the same dust emitter

   // 3rd person camera settings
   cameraRoll = true;         // Roll the camera with the vehicle
   cameraMaxDist = 4.8;         // Far distance from vehicle
   cameraOffset = 1.5;        // Vertical offset from camera mount point
   cameraLag = 0.26;           // Velocity lag of camera
   cameraDecay = 1.25;        // Decay per sec. rate of velocity lag

   // Rigid Body
   mass = 380;
   massCenter = "0 -0.2 0";    // Center of mass for rigid body
   massBox = "0 0 0";         // Size of box used for moment of inertia,
                              // if zero it defaults to object bounding box
   drag = 0.6;                // Drag coefficient
   bodyFriction = 0.6;
   bodyRestitution = 0.4;
   minImpactSpeed = 5;        // Impacts over this invoke the script callback
   softImpactSpeed = 5;       // Play SoftImpact Sound
   hardImpactSpeed = 15;      // Play HardImpact Sound
   integration = 8;           // Physics integration: TickSec/Rate
   collisionTol = 0.1;        // Collision distance tolerance
   contactTol = 0.1;          // Contact velocity tolerance

   // Engine
   engineTorque = 3300;       // Engine power
   engineBrake = 600;         // Braking when throttle is 0
   brakeTorque = 8000;        // When brakes are applied
   maxWheelSpeed = 50;        // Engine scale by current speed / max speed

   // Energy
   maxEnergy = 100;
   jetForce = 3000;
   minJetEnergy = 30;
   jetEnergyDrain = 2;

   // Sounds
//   jetSound = ScoutThrustSound;
//   engineSound = BuggyEngineSound;
//   squealSound = ScoutSquealSound;
//   softImpactSound = SoftImpactSound;
//   hardImpactSound = HardImpactSound;
//   wheelImpactSound = WheelImpactSound;

//   explosion = VehicleExplosion;
};

//-----------------------------------------------------------------------------

function WheeledVehicleData::create(%block)
{
   %obj = new WheeledVehicle() {
      dataBlock = %block;
   };
   return(%obj);
}

//-----------------------------------------------------------------------------

function WheeledVehicleData::onAdd(%this,%obj)
{
   // Setup the car with some defaults tires & springs
   for (%i = %obj.getWheelCount() - 1; %i >= 0; %i--) {
      %obj.setWheelTire(%i,%this.carTire);
      %obj.setWheelSpring(%i,%this.carSpring);
      %obj.setWheelPowered(%i,false);
   }
   
   // Steer front tires
   %obj.setWheelSteering(0,1);
   %obj.setWheelSteering(1,1);

   // Only power the two rear wheels...
   %obj.setWheelPowered(2,true);
   %obj.setWheelPowered(3,true);
}

function WheeledVehicleData::onCollision(%this,%obj,%col,%vec,%speed)
{
   // Collision with other objects, including items
   
   
}

I just want to make sure I understand this correctly

%obj.setWheelTire(%i,%this.carTire);
%obj.setWheelSpring(%i,%this.carSpring);

%this //meaning the model I am adding
.carTire // is the method of calling in the main model shape file


carTire = "fordCoupeCarTire";
carSpring = "fordCoupeCarSpring"; // this data is called/passed from the specific datablock being imported to the model

I just want to make sure I understand it, I start a C++ class tomorrow so hopefully I will get a better idea

#4 Correct, that will spawn your vehicle with its proper bits.

Now here's a little something else for you to know. The WheeledVehicleData::onAdd can be overridden by an onAdd specific to your datablock, which was originally the why I intended my answer to lead you, but the default stuff should work for you for now.

Basically you would only really need to override the onAdd when you start doing stuff to your vehicle that shouldn't happen to others, like for instance which wheels are powered, or the wheel steering, or even if you start adding turrets to vehicles.

#5 I think I understand what your saying.
I could have left the defaults in that function, and just added the datablock with the model and tire data and inherited the default spring/wheeledVehilce data from the default car datablocks.

#6 I tried something like this but I'm having the problem of the new cars WheeledVehicleData::onAdd function overriding the default car's tires so the default car ends up loading the new tires.