Final answer:
The inner circumference of the tire sidewall that sits on the wheel rim is called the bead seat, and it is essential for ensuring the car tire stays in place and is air-tight.
Step-by-step explanation:
The inner circumference of the tire sidewall is known as the bead seat.
This is the area of the wheel rim that the tire bead rests on. In a car tire, the bead is the edge of the tire that sits on the wheel; it's designed to stay snug against the rim, preventing air from escaping and ensuring that the tire stays in place.
As a result, the bead seat plays a critical role in the safety and functionality of a wheel rim and tire assembly.