Sledgehammer, you are correct; I found more information from Dave Morgan and this is what he said:
Before I say anything, I should begin by saying I have no doubts that the CalTrac bars offer an improvement in the traction of a car. The results are too widespread and too common to say otherwise. However, they do not improve the traction because they relocate the Instant Center (IC).
We define Instant Center as the center of the arc the rear axle moves around as it travels vertically. In this application, we also define the IC as a lift point (there are other ICs in the car that are also the center of an arc, but don't function as a lift point.)
In the case of the CalTrac bar, the front mount of the bar is on a pivoting shackle, which by it's nature means that the rear axle still rotates around the front eyelet of the leaf spring, which was and still is the IC of the rear suspension.
This idea was tried before in the '70s. Chrysler engineers designed a rear suspension called a leaf-link suspension which really did relocate the IC. It had a pair of upper control arms that were rigidly fastened to the differential housing and the chassis. The front of the leaf spring then functioned the same as the lower pair of bars on a fourlink, while the new upper bars did the same as the upper bars on a fourlink. In that design, there was no pivoting shackle for the front mount.
I had no idea the tuneable IC aspect was part of the CalTrac Bar patent, but I have had students and racers show me the instruction sheets that come with the bars.
Competition Engineering created a similar product called a Slide-a-Link which works on the same principle as the CalTrac bar. In this design, the lower bar has an inner tube and an outer tube that can be tightened to reduce the amount of sliding, or extension that these telescoping bars permit.
In both cases, I think all they do is reduce wheel hop by reducing, or eliminating, the spring wrap that occurs when a bunch of torque hits the pinion gear in a rear end.
I hope this helps.
Sorry, if my previous statement confused anyone.
Chris
