Remove stock endlink and install new endlinks. To eliminate sway bar preload (recommended), leave one endlink disconnected (other endlink should be connected). Place car (all 4 wheels) on flat ground. Then adjust the length of the disconnected endlink until the bolt inserts easily into the lower arm. That will be the length setting to use. Assemble and tighten that endlink accordingly.
It is important to ensure that the endlink has good articulation, because as the suspension moves up and down, the sway bar endlink needs to move in an arc. First check that the lower spherical bearing still has sufficient articulation. The following pictures demonstrate bad installation angle (first 2 pics) vs. good installation:
As a rule, you want the endlink to be as close to vertical as possible. If the bearing is not installed with sufficient articulation angle, then under suspension travel, the endlink will bind (ie. the endlink can no longer rotate freely) and will cause something to loosen or break. To obtain good articulation, you may need to use the supplied ring spacers (shown colored black in the following pictures) to move the endlink closer to the front (install with ring spacer but no cone spacer) or rear (install with ring spacer and cone spacer) of the car. This will allow you to match the distance to the installation hole on the sway bar:
It is also important to ensure the endlinks have good articulation in another direction of motion – the twisting motion, as seen below:
The following pictures show a bad install as well as a good install:
In the first picture, the endlink can no longer twist, the bearings are in such a position that one prevents the endlink from twisting left, and the other prevents the endlink from twisting right. The second picture shows a good install, the 2 bearings are oriented in such a way that if you grab the endlink and twist counter-clockwise, you can re-center both spherical bearings.
You need to make sure that the endlinks have good articulation after tightening down the jam nut (the nut between the lower and top bearing) and all the attachment bolts/nuts.
The following shows an endlink installed with Nismo sway bars, using the extra spacer between the endlink and lower arm. Note the good range of articulation available on the bearings:
Install nut that goes between endlink and lower control arm with blue loctite and torque to 25-30 ft-lbs.
Torque nuts attaching endlinks to sway bar to 25-30 ft-lbs.
Torque jam nut (length setting of endlink) to 20-30 ft-lbs.
Rear endlinks do not require any spacers, however make sure the endlink has good articulation in the twisting motion. The following shows a properly installed endlink:
Torque nuts attaching endlinks to sway bar and upper arm to 15-20 ft-lbs.
Torque jam nut (length setting of endlink) to 20-30 ft-lbs.