Which type of arm is typically absent in a MacPherson strut suspension?

In a MacPherson strut suspension system, the design simplifies the suspension architecture by utilizing a single strut that combines the functions of the shock absorber and the spring. The key feature of this system is that it typically does not include an upper control arm, which is a component commonly found in other suspension designs.

The absence of the upper control arm in a MacPherson strut setup allows for a more compact design, reducing the number of parts and potentially lowering manufacturing costs while still providing effective handling and ride comfort. In this suspension type, the strut itself serves as the pivot point for steering and provides lateral support, contributing to the overall alignment and functioning of the wheel.

The other components mentioned, such as control arms (both upper and lower) and trailing arms, may serve various roles in different types of suspension systems or configurations. However, in the context of the MacPherson strut suspension, it is the upper control arm that is specifically not present, making this choice correct.