Before measuring for your steering system you need to make sure the front end is in fairly close alignment. After installing your system yo need to make sure your front end is perfectly aligned to insure maximum tire life and handling.
PREPARING FRONT END FOR TIE ROD & DRAG LINK MEASUREMENTS (with the front end in, or out of the vehicle)
Before measuring your desired tie rod, drag link and track bar lengths, you first need to insure that your front end is correctly aligned in order to provide us with accurate measurements. There are several methods to achieve this, depending on what current state your vehicle is in. We will cover some of these methods in order of preference, based on what works the best and is the easiest and most accurate. You choose which method will best apply to your situation. Desirable toe-in settings would be between 1/16" and 1/8" measured from rim to rim in relationship to the center of the pivot point of the knuckle. That result is double this measurement in the difference from the front of the rim to the back of the rim. Remember, if the rim is 15" in diameter, measuring at the outside of a 30" tire will "double" the difference, and as the tire grows, that difference will increase exponentially.
BASELINE SET UP First thing to do is position the passenger side knuckle perfectly 90 degrees to the centerline of the axle housing as a baseline for other measurements to be made from. With a large carpenters square, place the inside edge across the face where the rim bolts to, or if the drum/rotor is not installed, across the face where the spindle bolts to the knuckle. Move the knuckle until the long end of the square is perfectly parallel to the axle housing. Now you can simulate the vehicle going down the road straight where a proper drag link measurement can be predicted. You can now also work off this base to position the driver side knuckle to make it parallel with the passenger side to make your tie rod measurement, as outlined below and as illustrated here.
PREPARATION FOR AND MAKING THE TIE ROD MEASUREMENT With the front end in or out of the vehicle, affix a metal straight edge (horizontal and parallel to the ground) to the mounting face of each side of the hubs where the rim is bolted to, since that should be a flat surface and best replicates the absence of measuring the rim lip itself. A pair of inexpensive metal yard sticks work well. If the brake discs, hubs or drums are not on, affix the straight edges (with tape or clamps) to the flat mounting surface where the spindles bolt up to. Measure across from straight edge to straight edge and adjust the DRIVER side knuckle until the distances are even front to back, since the passenger side knuckle is already parallel to the axle by the initial baseline setup with the square as outlined above. Now measure from knuckle to knuckle for the tie rod length from the center hole to center hole distance as illustrated here.
DRAG LINK MEASUREMENT The front end must be in the vehicle for this but there does not need to be any linkage installed. Insure that the passenger knuckle has not been disturbed from the initial baseline set up using the square. If you suspect it might have been disturbed, re-square it again at this time. Spin your steering wheel lock to lock and count the total revolutions and divide in half, and position the steering wheel that amount of turns from one side. As an example, if the wheel turns a total of 4 times, then 2 turns from either side will locate the pitman arm in it's center most position. Once this has been achieved, measure from the pitman arm to the passenger knuckle on the center to center distance as illustrated here.