OK - now I am going to have to do some research. But first here is what I "think".

It has been my understanding the IC is the EFFECTIVE lifting point of the suspension system not the mounting point of the suspension. This effective point is determined by the force vectors created by the mounting points. A 4-link IC is not at its mounting point but at an imaginary intersection point of the force vectors created by the bars.

So wouldn't the cal-trac bar be transferring an "effective" lift point different from the spring mount? Thereby changing the IC? It is at a different angle than the spring. With the spring wrap the shortening the front segment, it is effectively the top bar of a four link, and the leverage of the Caltrac bar being mounted lower than the axle, getting pushed forward, it would effectively be the lower bar of a four link. Changing the relationship between the two should move the effective IC. And moving the cal-trac bar up or down will change the forward force point, which would mean the IC would change.

My curiosity is peaked on this one, so I will go hit up a couple of PE's for answers.

Also, just because a system has more adjustment points (more IC's) doesn't make it "better" Only a few of the IC points are even close to correct on any given car even with a four link.

Don't get me wrong, I fully believe a leaf spring system is much less than ideal, but it can be made to work fairly well on many cars. Just for reference my last "street" car was a ladder bar setup and my new one is a true four link.

And looking back at an earlier post, I don't see the RMS Street Lynx having less strength than the Unlawful unit. Both have solid top and bottom bars, both mount the lowers at the original spring perch and the top bars to a bar welded between the frame rails. Both bolt to the housing using U-bolts. The RMS has three U-bolts per side, and I only see two in the posted Unlawful picture. Both allow for larger tires than leaf springs.

I do like the RMS Lynx having the shocks mount in front of the rear end housing, making it fit much more easily in a A-body even with the spare tire well.

So I guess it boils down to prices vs performance goals/gains.

Cal-Tracs w/ mono springs and rancho shocks - $815
RMS lynx - all parts included w/QA1 shocks $1795
Unlawful w/all parts included $3995
4-link $4,000 to - $9,000 depending on who, and what is done.

Scott