BMR vs UMI Rear LCAs (with Roto-Joint modifier)

While I completely agree the separate
" divorced " sway bay is a better set up, the old slap it on the lower arms 1.25 Hotchkis wagon specific bar does work.
Personally if I were looking at over the counter arms, I would be considering the double roto joint.
Mine are home made but similar design.

There was a noticeable difference ,binding wise ,over my old poly set up.

As noted above, extended arms and skirted wheel well cars do not mix.

Pretty much echoing what was said but just going to add my own take to things that i've learned from experimenting with a few different setups on different B bodies i've owned. First I'll address the problems i've seen with various rear suspension setups.

1) poly bushings. They suck, period. We're on a quest to reduce deflection, but poly bushings introduce a ton of bind. They just aren't meant for this application. With that said, Delrin insulated spherical bushings like Roto Joints or Johnny Joints are best, but if you have them at both ends it could make for a harsher ride with more road noise/vibration transferred into the chassis. I also have found that arms using two spherical ends tend to wear out the spherical ends faster, I assume from impacts, versus having a soft bushing at one end. I came to a compromise and used a rubber bushing in the axle end and Johnny Joint in the chassis end of my upper trailing arms. For my lowers I'm running a johnny joint in the chassis and a poly in the axle, which i'm not happy about, but the poly doesn't seem to bind as much at that location than in the upper. Again, Ideal from a performance standpoint would be 4 spherical bushings, the rubber/poly at the axle and spherical at the chassis is a compromise performance wise, but I feel it keeps bind to a minimum while somewhat insulation the chassis from vibration.

2) when extending the upper arms and using a rubber bushing in the axle end, one thing you will notice is the angle that the clevis meets the bushing will change as you move the rear back. I welded up my own upper arms with an offset clevis so it meets the bushings square. A few brands used to make this, but I don't think any do anymore which is a shame. If you use spherical at both ends, it doesn't matter.

3) as important as reducing deflection at the bushings is, it's my believe that you will have a better performing suspension setup by focusing on what's around those bushings just as much as the bushings themselves. DMR bars will stiffen up the mounting points, an RMS bar will help reduce flex in the rear crossmember. The tubular or boxed arms themselves will significantly reduce flex in that arms that changes suspension geometry. IF all of that is addressed, I actually wouldn't be surprised if even rubber bushings all around wouldn't still perform great.

4) the chassis mounted sway bar IMO is definitely a good upgrade. I went with a SpeedTech bar on mine. The the bind caused by the LCA mounted sway bar gets worse as you stiffen up the sway bar.If you're running a factory bar, it probably isn't an issue, but as you try to reduce body roll more with a stiffer bar, you will end up introducing more bind.

One of the biggest things I've learned on these cars is a lot of the typical things guys do to them (stiff shocks, stiff springs, big sway bar, poly bushings) make for a very good CORNERING car but a very poor ride quality caused by a suspension that isn't articulating freely. My goal for my latest setup was to reduce bind in as many places I can to make for a car that could not only corner, but confidently corner around a bumpy turn (as well as a solid rear car could, anyway). One thing I've noticed in the B bodies I have modded and driving other modded suspension B bodies with the typical suspension mods that don't address bind is they have a tendency to skip along the road on less than track like smooth surfaces. The rears have a very hard time staying planted, and it makes for a very crappy ride on the street unless you live someplace where every road is as smooth as a race track.

I'm going to vote against spherical type bearing on the control arms - They are functional, but not long lived in real life road conditions.

I went with the SpeedTech setup since it uses firm bushings on each end but the bars themselves articulate to eliminate any suspension bind. The control arms are made in two pieces which thread into each other and are sealed with an o-ring to keep crud out. These are big threads (1.5") so can take the loads. This also allows you to center the rear end (if necessary) and adjust pinion angle easily. This does not allow the use of OEM type control arm mounted sway bars though so keep that in mind.

We seem to have similar goals in handling so we'll see what we can learn from each other

Speed Tech used to have a good page that described how the arms work, but I can't find it now with their updated website. The installation instructions are the next best thing...

You might want the use "tube" and weld ends
I'll have to go measure (like you could)

EDIT 2.65"

Also, round lower arms pretty much stops you from mounting a production style rear bar .
Yeah people , and retail companies, have done it, but it invites arm failures.
Pretty much every broken aftermarket rear arm on this sight was round with either a plate weld on or tubes welded through for a sway bar

The thing I am not enamored with on the Johnny Joint it is non adjustable.
Press it together, put the circlip in.

Rubicon and others if you look about, have adjustment rings so you can get and keep the preload just as you want.
That said, it has been a long while and I have never adjusted them
It looks though, I should buy some spare parts while I can.