74_5.0L_Z

Looks good. Except for the two picture that look like neck X-Rays. What is the side to side distance between your LCA mounting holes? How Long is the slot?

I am ready for others to enter the discussion. Specifically, if you have dimensions of components or chassis points, please post them here. We can begin to use the tool to compare suspension geometry modifications.

Before I distribute this to the whole community, I would like to test drive it with some of the senior members. Specifically, I would like to give copies of the Suspension Analysis tool to Jon Mortensen, Cary McCallister, John Coffee, and other with significant suspension experience or with knowledge of the stock S30 geometry. If you guys could PM me with email addresses, then I will send you a copy. I am ready for other to enter the discussion. Specifically, if you have dimensions of components or chassis points, please post them here.

Discussion of Math Model in images below. If you are an engineer, a math geek, or a glutton for punishment, feel free to read the discussion below. If you only care about the end result start at page 9 and 10 to skip the math. The only way I could present the discussion of the analysis was using images of my analysis in word.

Steering Rack The critical dimension of the steering rack is the spacing between the centers of the inner ball joints. The measured spacing of the stock S30 rack is 24.25 inches center to center. The rack is placed via the cross member such that its center line runs parallel to the chassis Y axis of the base coordinate system. When the steering wheel is centered and the wheels are straight ahead, the centers of the inner tie rods (in my car) are located such the right inner tie rod is located at (80.75, -12.13, 3.12), and the left inner tie rod center is located at (80.75, 12.13, 3.12). When the steering wheel is turned clockwise, the right side of the rack extends, and the left side retracts from the rack housing. The rack can extend a total 2.39 inches in each direction. So, when the steering wheel is turned all the way to the right the center of the right inner tie rod ends is located at (80.75, -14.52, 3.12), and the left at (80.75, 9.74, 3.12).

Front Cross member The factory drawing does not provide the dimensions of the front cross member nor does it give the coordinates of the attach points between the frame and the cross member. On my car the entire front frame has been recreated using tubing, but I used the FSM dimensions as a general guide. The height and spacing of my frame rails are the same as stock. They are 25.1 inches apart and the bottom surface of the frame rails are 5.12 inches above the base coordinate system. The attach points between the frame and my cross member (which are not stock) are as follows: The front mounting hole is 23.625 inches forward of the firewall and 15.063 inches from the car's centerline. The rear hole is 3.5 inches aft of the front hole. When I was measuring all of this stuff to try and get a handle on my geometry, I found that the old cross member was pretty distorted from years of abuse and several cycle of modification, so I decided to make my own to allow me to easily change the LCA mount height and to easily change the mounting position of the steering rack. The cross member moves the attach point of the LCA forward, but leaves the rack in its original fore and aft location. The rack height is adjustable by changing the thickness of the spacers below the clamps around the rack. The slot is located 12.13" from the centerline of the car and allows the height to be adjusted from 1.21 " to 2.21 inches above the base coordinate system. The height of the LCA attach point is adjustable in a slot that accepts Allstar Performance Caster slugs. Currently, the LCA is as high as the slot allows. The table below give the locations of the LCA hole in the stock cross member, the JTR modified cross member, and my cross member. Table 2: Position of LCA Attach Point relative to Base Coordinate System. My Cross Member Stock Cross Member JTR Modified Crossmember Point Description X Y Z X Y Z X Y Z LCAR Center of Right LCA attachment to Cross-member 77.2 -12.13 2.12 TBD -11.625 1.56 TBD -11.875 2.31