Here is a sample offset chart. The offset that the car was raised must be the same at all
Start by measuring the LF corner, then move around the car clockwise to adjust the other three corners to a dimension equal to their ride height plus the offset amount. Then make sure that the chassis is fully supported at all four corners and does not rock or roll. You can shim one of the rear corners to stabilize the car, usually the RR. As long as the two front corners are set to ride height plus the constant offset and tight on the jack stands, then you will be OK.
Step 5 Remove the front springs and shocks and jack the LF and RF wheel assemblies up until they are positioned so that you have the same measurements as we took in Step 3. Install a link in place of the shock at each side so that the wheel assembly is supported in the same position as if it were at normal ride height with all of the weight on the tires (Step 3 measurements used).
The link can be a strut rod or tubular control arm with opposite threaded Heim joints of a usable length. This type of temporary link is easy to install and adjust for length.
If those are not available, then a piece of 1-inch by 1/8-inch iron or aluminum strap metal can be used. Drill a one-piece link the exact length of the installed height of the shocks for each side. Or, you can cut a piece in two so that they are long enough to overlap when installed in the shock mounts, drill a hole in one end of each piece and bolt the two to the shock mounts.
With the wheel assembly positioned correctly, overlap the straps and lock them together with a pair of vice grip pliers. Drill another hole through both pieces and bolt the two together. Label each set of straps, i.e. LF, RF, so that you can reuse them if you need to remeasure later on. Once the two wheel assemblies are secured in their proper positions, remove the tires and wheels.
The best way to support the spindle while taking MC measurements is by using a spare contr
Step 6 Establish and mark the center of rotation of each ball joint. It is important to know the exact location of the pivot point of the ball joint so that we can mark that point on the ball joint support band on the control arms and measure to it.
To find the center of each different type of ball joint, we can quickly locate it using a simple method of placing the ball joint in a vise with the stud pointed up and then lining up the shaft as it moves from side to side.
Now that we know where the center of rotation is located in relation to the band, we can mark a point on each ball joint on the car. Remember to allow for anti-dive angle in the control arms as well as the control arm angle. These angles will affect where you place the point to measure to.
Use 3/4- or 1-inch wide masking tape and place a piece over the ball joint band. Clean the surface first to remove all grease and dirt. Use a fine tip black marker and a small straight-edge to make a cross on the tape to represent the center of the ball joint for height and width measurements. Do this for the upper and lower ball joints.
Step 7 Take all of the height measurements first. If a direct vertical measurement cannot be taken, then use a level to project the height out from each point or construct a fixture to use to represent the distance so that a measurement can be taken away from the car.
When measuring the lower chassis points, use the pivot that is closest to a line lying at right angles from the ball joint to the centerline of the car. For the stock GM lower control arms, use the center of the front bushing. For a strut-type of lower control arm, use the center of the bushing or center of the Heim joint that is on a line laying 90 degrees off the centerline of the car projected through the center of the ball joint.
The upper chassis mounts often have antidive. To measure the chassis pivot point, average the heights of the centers of the two mounting bolts and measure the width to the center of the control arm shaft. In the case of an upper control arm that uses Heim joints, measure to the pivot that is closest to a line that would be laying perpendicular to the centerline of the car from the center of the ball joint. If the two mounts are equal-distant from the perpendicular line, measure to both and average the measurements for height and width.