Control arms or “A” arms or maybe “wishbones” are the components that attach the spindle/brake assembly to the frame. In almost every case there is an upper and lower arm. The lower arm is the big one, supporting the weight of the front end through a spring or torsion bar. The lower arm is where the actual lowering takes place. This is done by moving the spring perch down and lower ball joint (which attaches in the spindle) up relative to each other and the frame. Upper control arms attach to the spindle through the upper ball joint (in the spindle) and to the frame through shaft or pivot points. Upper arms have no influence on ride height but has a great deal of influence on alignment.