DionR said

So, using my "basic" performance setup which is:

LCA flat
1 degree negative camber
6 degrees positive caster
275/35R18 +35mm wheel

The roll center numbers potentially are:

A-Body spindle - 5.5155"
F-Body Spindle - 6.6873"
F-Body w/ 1" ext BJ - 8.7916"

In comparison, the stock suspension roll center looks to be at 6.9489"

The other (maybe?) useful data point might be the height of the LCA pin:

Stock - 12.3684"
Performance - 10.3946"

Or almost 2" lower.

If we take these numbers and do some comparisons, here's a couple of things that jump out to me.

The stock A-Body on the performance setup is lower by 1.9738" but the RC dropped by 1.7939, so the roll couple is shorter by 0.1799". Not much, but still a shorter roll couple. Add that the center of gravity (CG) of the front of the car is down almost 2", the LCA isn't at a leverage disadvantage (side load could result in jacking in the stock orientation) and it doesn't look like it is ready to go rock crawling (no offense intended to the stock 14" wheel crowd, well ok, maybe some offense intended). So it makes sense this setup would be superior to stock.

The F-Body spindle with the same ride height drop only loses 0.2616" of height for the roll center but with the CG being 1.9738" lower the roll couple is actually shortened by 1.7122". So a lower CG and shorter roll couple suggest a win-win.

The f-Body spindle with the extended ball joint actually has a taller roll center by 1.8427" and when added to the CG drop, the roll couple is 3.8165" shorter than stock. That can't be bad, can it?

Now this flies in the face of the idea that you want a 2-4" height for your roll center. After doing some reading, I am leaning towards the thought those numbers really only apply if you already have a low CG already. I think a short roll couple is the key provided you keep the CG low and you don't have the control arms at wonky angles.

I understand that you can tune for a large roll couple with a bigger sway bar and stiffer springs, but it makes sense to me reduce the roll couple if possible rather than have to work against it.

This further solidifies my opinion that the stock TB suspension has (potentially) the best geometry of any of the Mopar A-Body systems available on the market.

Click to expand...

DionR said

This is my current idea for the hub and caliper mount:

View attachment 1716394476

The difficult thing for getting the rotor located correctly is the back of the hub to caliper mount surface. My previous idea had used several stacked plates to make up the offset, which worked ok and even accounted for the LBJ bolts and captured them in the spacers.

View attachment 1716394481

View attachment 1716394482

The problem is that plate is that there is a tolerance on the thickness and the more plates you stack up, the more potential variation compared to the target thickness.

I am hoping that a part that is CNC bent by SendCutSend might have better potential for hitting the target.

View attachment 1716394485

The small slots are so the bends don't distort anything. These would get welded up in the final assembly.

This comes with some concessions in that nuts need to be welded.

View attachment 1716394486

It also has tubes and plates to fill in the corners.

View attachment 1716394487

The other bigger change was a single 1/2" plate for the caliper mount ears instead of two 1/4" plates. I figure the thickness tolerance doesn't matter if the spacer assembly sets the offset from that surface. It might vary the overall track width a touch, but I doubt it is more than the factory tolerance.

That's as far as I got on it. Have to build the UBJ mount and figure out what that might look like.

Click to expand...