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.
ALIGNING THE FRONT END IN VEHICLE FOR TIE ROD & DRAG LINK MEASUREMENTS
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.
ALIGNING FRONT END WITH TIRES ON, WITH OR WITHOUT LINKAGE INSTALLED Preparing for measuring the Tie Rod... Park your truck in a well lighted area and kneel down 10 feet directly in front of the passenger front tire. Line your eye up with the forward and rearward face of the rear tire's outside sidewall and use it like a "gun sight" to aim yourself to get directly in line with it. Now, compare the front tire's outer side wall to the rear, also aiming it like a gun sight. Adjust the front tire to line it up with the rear. Sometimes the front stance is wider then the rear, if this is the case then adjust the front tire to make them parallel with each other.
Now move to the driver side and use the above aiming method once again. If you do not have a linkage installed, then adjust the driver tire just like you performed at the passenger tire. If a linkage is installed, then adjust the linkage to make both tires straight inline with the rears. Remember when you adjust the linkage, this may affect both tires, so you will need to repeat the passenger side procedure as well as the driver side procedure every time to make a linkage adjustment. Now you can take your tie rod measurement on the center to center distance as illustrated here.
ALTERNATE METHOD: The String Procedure- If you do not have ample space or lighting to perform the above visual procedure, then simply tie a string around the rear axle housing and draw it around the backside of the rear tire, pulling it forward well past the front tire. Keep the string the same height as the center of the hubs. Now compare the sidewall alignment from front to rear using the string a type of straight edge, and try to make them as parallel as possible by adjusting the front tire's position. Repeat for the other side.
FRONT TIRES LINED UP WITH REAR TIRES
Preparing for measuring the Drag Link... Once the front tires are inline with the rears, you now you can measure for your Drag Link length. If you do not have a linkage installed, then spin your steering wheel lock to lock and count the total revolutions and divide in half to 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.