What component is NOT part of a rear MacPherson strut suspension system?

The upper control arm is not a component typically found in a rear MacPherson strut suspension system. In a MacPherson strut design, the suspension consists primarily of a single strut assembly that combines the shock absorber and spring into one unit. This strut is mounted to the vehicle’s body at the top and connects to the lower control arm at the bottom.

The other components mentioned, such as the lower control arm, steering knuckle, and shock absorber, play integral roles in the functionality of the suspension. The lower control arm connects the strut to the vehicle chassis and allows for vertical movement of the wheel, while the steering knuckle attaches to the wheel hub and the strut, enabling steering and support for the wheel assembly. The shock absorber is part of the strut in this system, helping to manage ride comfort and stability by dampening the oscillations of the spring.

In summary, the upper control arm's absence is characteristic of the MacPherson strut design, distinguishing it from other suspension systems that do include an upper control arm for additional support and alignment.