Upper vs Lower Control Arms

Question

Doing research into some front end suspension components, I found this odd mixture of the need to clarify the upper and lower identity of control arms, even in the absence of an upper control arm.

I gathered so much as upper and lower control arm pairs mainly apply to trucks and perhaps large vehicles that need that extra type of stability. Is that accurate? My vehicle only has one control arm, so the need to specify upper or lower seems odd.

For example if you see this part, it is qualified with lower: Volvo Control Arm Bushing Front Lower

Is there something else that designates whether a control arm is upper or lower, perhaps not so much a vertical stacking thing but maybe a part of the vehicle frame it is fastened to?

Answer 1

Suspensions that use upper and lower control arms are plenty. They are found in much more than trucks. Sports cars often have these types of suspensions because they can have lower unsprung weight compared to say a McPherson suspension.

The naming convention comes from the attachment to the knuckle. If the control arm attaches to the bottom on the knuckle, it is the lower control arm. If it attaches at the top, it is the upper control arm.

There are vehicles that have multiple lower and upper control arms and then a further complicated naming convention is needed.