There has been much discussion over the years about the binding issue in the stock rear suspension. Some say that the angled Upper Control Arms (UCAs) are the culprit. The methods to resolve it typically include some fairly invasive updates.

Instead of Panhard bars, tri-links, and other changes, what if we straightened out the UCAs? Would that alleviate the binding?

Proposed plan:
1. Convert the rear suspension to coilovers (remove the separate rear springs)
2. Remove the rear spring perches
3. Relocate the UCA axle brackets inboard (where the spring perches used to be)
4. Modify the UCAs to be straight instead of angled (cut & weld)

Benefits:
A. No cutting / modification to the car body
B. Able to use cheap polyurethane suspension bushings without exacerbating the binding issue

Thoughts?

 

Highly recommend modification!
The way I did it is not for the faint of heart because it puts the front on a single sheer attachment.
Originally I planned something like what you are thinking but for testing I did this and it worked so well I never changed it.
It's been years like this @ 400rwhp on a 225/45/16 Dunlop with no signs of fatigue, proper grade hardware, spacers, washers is important.
Just for clarification the bolt extends all the way through the inside bracket and a spacer takes up the space in that stock mounting bracket.

 

Wouldn’t you use wheel clearance with the bar mounted outside?

I would like to see the OP do it and what the results are.

 

Here is an E Production race car solution. The OE upper arm bracket is retained and a new mount is added in the fender well. The new mount is supported internally so even though it is a single shear mount the bolt is supported for 4-5 inches. The lower control arm mount is lowered 2.5" below the stock location to correct suspension geometry because this car is lowered quite a bit. As far as tire clearance, these cars run flares so not a concern, but there is allot of real estate in the rear fenders so I think there would be room for this.

 

My car is a summertime daily driver (I live in Michigan, so I don't subject it to wintertime salt), and I don't want to ruin the "cream puff" essence. When a friend who used to own a modified GSL-SE rode with me, his first two comments were: 1. "It rides so well!" and 2. "It's so quiet!" Therefore, I plan to use modified OEM control arms to retain the isolation.

Since the ends of the OEM control arms are so large, and I'm running 245s in the rear, I'll probably have to go with my original plan to ensure clearance in the wheel wells.

Thanks to all for the comments.

 

You will also need to make the arms the same length as the lowers, or as close to it as you can get.


The binding is because any angled 4 link will have its own roll center, and this one is different than the one the Watts link has. This is part of the reason why the Watts link is so high up, because the 4 link's roll center is even higher than that. (You can drive an RX-7 with no Watts link just fine. The roll center is way up somewhere between the deck and the roof but bushing compliance means that axle can move around enough laterally that it doesn't matter too much)

I had been thinking about it once and realized that if you moved the LOWER links to a complementary angle in plan-view, that would change the 4 link's roll center significantly.