I am using the following code to attach wheels to a car:
tire_rear = instance_create (x+rear_wheel_x, y+rear_wheel_y, rear_wheel_type);
physics_joint_wheel_create(id, tire_rear, tire_rear.x, tire_rear.y, 0, 1, false, 0, 0, wheel_joint_freq_hz, wheel_joint_damping_ratio, false);
tire_front =...