public VehicleWheel addWheel(Vector3f connectionPoint, Vector3f direction, Vector3f axle, float suspensionRestLength, float wheelRadius, boolean isFrontWheel) {
        return addWheel(null, connectionPoint, direction, axle, suspensionRestLength, wheelRadius, isFrontWheel);
    }
Add a wheel to this vehicle
@param connectionPoint The starting point of the ray, where the suspension connects to the chassis (chassis space)
@param direction the direction of the wheel (should be -Y / 0,-1,0 for a normal car)
@param axle The axis of the wheel, pointing right in vehicle direction (should be -X / -1,0,0 for a normal car)
@param suspensionRestLength The current length of the suspension (metres)
@param wheelRadius the wheel radius
@param isFrontWheel sets if this wheel is a front wheel (steering)
@return the PhysicsVehicleWheel object to get/set infos on the wheel
jme3-jbullet/src/main/java/com/jme3/bullet/objects/PhysicsVehicle.java