How to use Mathf.Clamp with child objects?

In my game I'm trying to make the front two tire's of a car move left and right, like in a normal car when you turn. The actual movement of the car is perfect and ready to go, and I even got the tire's to move left and right, but I can't restrict their rotation with Mathf.Clamp. It's probably because they're child's of the car. I get them to rotate by rotating them around the global y axis, could that also be a problem? Anything will help thanks a bunch!