How to get steer angle of wheel collider

Hello,

I am a beginner of unity.
I am learning the unity by leading sample projects -Car tutorial-.
Now I want to know how to get current steer angle.

Reference of unity said that -Wheel collider always keep the steer angle-.
Therefor I added the code into the update function of Car.js such as follow.

function Update()
.....
for(var w : Wheel in wheels)
{
var wheel : WheelCollider = w.collider;
if (w.steerWheel == true){
Debug.Log(wheel.steerAngle);
}
}

But I could not get it.
And I tried to add following code into the UpdateWheelGraphic function.

function UpdateWheelGraphics
.....
if(w.steerWheel){
w.wheelVelo *= 0.9;
//And I tried to add following code here.
steerAngle = wheel.steerAngle;
Debug.Log(steerAngle);
}
else
w.wheelVelo *= 0.9 * (1 - throttle);


But I could not get it at hear also .
So, What wrong my additional code?

thank you,