We have been building Anti-Roll Bars for quite a long time. 20 years now, actually.
You will see a variety of styles and options. OUR goal, is to offer an anti-roll bar that our customers can install, set, and go. No disconnecting, etc. The only way to truly have an ARB that you can do that with (install and drive on street without worry), is to use a poly mount bushing on the main bar.
We engineer and test our parts for optimal performance, so you will see us occasionally revise our components. In the case of our ARB, the primary reason for the revisions was to get a lighter piece, that works the best, with the ease of use and install in favor of the customer.
Here is an example:
So - here is our "original" S197 ARB: (very similar to the Spohn you posted)
I got this pic from our old web-site....Pretty cool, our site back in early 2006!
https://web.archive.org/web/20060221100439/http://www.bmrfabrication.com/2005Mustang.htm
Here is our first redesign:
Here is our Current:
On the first design, one of the issues was that no matter how "stiff" we went on that bar, it would not work much better than a super heavy duty OEM style sway bar.
We believe it is because of how far we went inboard on the mounts, reducing the sway bar wheel rate. (reduced roll stiffness, as sway bar mounts move closer inboard)
We also believe that attaching to the chassis AFT of the axle housing, helps the bar do a better job.
So, we designed the second gen ARB, to have mounting points that were as far outboard as possible, while retaining exhaust clearance, ease of install, etc. We also moved the body mount AFT of the axle.
Our 3rd design (current) was done to save weight, add on car adjust ability....and we wanted to make the bar completely in house.
**The 2nd gen, we used a splined bar that we sourced out.
There is no doubt that a solid / all bearing ARB will have a better working rate, when launching......BUT, you have to look at the engineering of the bar. If you have a bearing set-up, that is narrow...and does not mount as far outboard as possible, you may run into our Poly mounted bar working very close to the same, in terms of actual wheel rate (total)
This also brings up the style that you asked about. They do use a Poly bushing....AND they utilize somewhat narrow mounting points. So, while they will definitely add roll stiffness compared to an OEM bar, they likely will not add enough to truly matter, unless of course it's a 2" OD bar.
That brings up another point. We have found, with our design.....MOST people have success simply using it set to neutral. This is a very good thing IMO, and solidifies how well the bar works.
When someone ends up having to set a ton of preload into the bar, to get the car to launch straight.....that leads to other issues, like the car being harder to control down the track....tires unloading on shifts....etc.
So, the moral of my post is - we are fans of poly bushed Anti-Roll Bars on the S197. The poly bushing is not as "good" at preventing body roll, however the style of our mounting helps overcome that.
The available bars that mount backwards to the axle, or - the main bar mounts to the axle.....typically do not provide the amount of roll stiffness that you want as a drag racer. Our 4th Gen ARB are very similar to the one you are asking about, actually:
So - if you have any questions about them, please ask away.
I could talk all day long about ARBs.
