Here's how to install adjustable upper control arms on an Infiniti or Nissan.
When a vehicle's suspension is modified or out of alignment, adjustable suspension components must be installed to bring the vehicle's tires back into alignment.
Notably on vehicles with double-wishbone front suspension, the lower control arm sits at an angle when the vehicle is lowered. The upper control arm follows that angle, causing the steering knuckle to pivot outward. This is called a camber angle change, which can cause excessive tire wear on the inside edges of the tire.
To combat this, an adjustable upper control arm, of which the ball joint can slide outward is installed to bring the tire contact back perpendicular to the road surface. The upper control arm also has caster angle adjustability.
In this video, adjustable upper control arms are installed onto an Infiniti G37x. The procedure is the same for the Infiniti G35, G35x, G37, EX35, G25, M35, M45, Q50, Q60 and Nissan 350Z and 370Z.
The upper control arm is held on by a 14mm pinch bolt and two 14mm bushing bolts. To free the rear bushing bolt, depending on the suspension installed, the coilover must be unbolted from the strut tower, and the lower control arm either pried down or jacked up to get the bolt to clear the spring. The same trick works to reinstall the bolt.
Adjustments to the new control arm are controlled by a caster plate (which is rotated in 12 different positions) and a ball joint that slides on a track. The ball joint is positioned roughly where the OEM control arm ball joint is (a measurement from the bushing to ball joint distance will confirm this initially) and the ball joint nut secures it in place.
Once installed onto the vehicle, the wheel is installed and the vehicle can be put on an alignment rack. The caster is controlled by moving the ball joint outward/inward, then the 27mm nut is snugged. On lowered vehicles, final adjustment torque must be achieved with the control arm loosed away from the knuckle, since a torque wrench cannot clear the fender to torque it to 120 ft-lb.
The upper control arms used in this video were from Mevotech, part numbers CMS301148 and CMS301147.