First, start with the main leaf measuring from center of front eye along the curvature of the spring to center of center pin {A}, then measure along curvature of the spring from center of center pin to center of rear eye (B). Then measure width of spring. Leaf counts, as well as ID of bushings, are important to determine stationary and shackle bolt diameters. Free height or unloaded arch is measured by taking a line from center of one eye straight across to the center of the other eye and measure from there at the center pin to the top of the main leaf (C). Pack thickness is measured at the center pin (D).