AZ RCA set-up

[gnosez]

I am looking for some initial set-up specs for the Arizona Z Car adjustable rear control arms as I rebuild my 240 suspension.

 

Prior to taking down the entire front and rear struts, control arms and the cross member with the steering rack (replacing with a reman), I rechecked the corner balance numbers, took measurements of the alignment settings (camber, caster, toe), the ride height, and the center to center distances between wheels (found a difference of 5/8 side to side).

 

The AZ RCA allows for several adjustments including:

 

1) control arm (front to rear)

2) control arm (angle - need to remember to check CV binding issues first)

3) track (width)

4) toe

 

The center to center (tube of the stock RCA to the spindle pin) is 14.5 inches

and I was planning on using that as my starting point to set the AZ RCAs but wanted to check and see if anyone here has installed these arms and has some advice they wish to offer.

 

Worst case I'll get it close and trailer it to the alignment shop but I'd like to

be able to test drive the car for other reasons prior to the alignment appointment.

[JMortensen]

If you're determined to use those arms, then DO NOT adjust #1. If you move the arm fore or aft, you'll screw up the relationship between the strut and the camber plate, essentially putting a nasty load on the strut shaft, which transfers through your monoballs to the control arms and the mounts on the inboard end. In fact, I would assemble the suspension, keep the bushing caps loose, then compress the suspension, and THEN tighten down the bushing caps in order to prevent any issues there, ESPECIALLY if you're using a camber plate with a monoball where there is no give (compared to using a rubber isolator on top for example), and then move the suspension by hand through its full range of motion to guarantee that there is no bind in theory. In practice that H arm suspension is unfortunately pretty prone to binding and your suspension components will be dealing with it.

 

2. For a typical race Z you'd probably want the control arms as high as you could get on the inboard pivot to get the roll center back up (this assumes a very lowered car). This unfortunately gives maximum leverage on the bracket to try and spin that gold bracket piece in the bushing caps and also minimizes track width. I realize there is a 1/4" bolt keeping that from rotating, but that doesn't convince me that it is not a problem.

 

3. Track width can be minimally adjusted with the rod ends. Aurora suggests 1.5x the thread be enclosed, which on a 5/8" rod end means you have about 5/16" adjustment before you exceed Aurora's recommendation:

 

http://www.aurorabearing.com/technical-resources/faqs/default.html

* What is the minimum thread engagement required to support the advertised load ratings in the Aurora Bearing Company catalog?

* The minimum thread engagement is 1.5 times the major thread diameter unless otherwise stated.

So you have a max adjustment there of 5/8" per arm, not considering whatever toe setting you're looking for.

 

4. You'll need to see where you're at first. I don't think your likely to get both rod ends in exactly the same depth front and rear. Each 180 degree rotation of the rod end will give approx 1/8" of toe change.

[gnosez]

Jon - thanks for taking the time to provide a very useful reply. It made me go back and check all my assumptions and measurements.

 

In particular your first point regarding the stress on the camber plate mono-ball issue was dead on and I went back and took more measurements so that I can line up the strut and CV (fore and aft).

 

The easiest way it seems is to use the inner rear diff carrier and draw a line out. That line on a stock RCA is very close to the center of the bottom of the strut tube and puts the CVs directly in line with the diff.

 

As to your 2nd and 3rd points on center tube angle and track width, this is the very reason I got this type of RCA. None of the others I have seen would give me back that angle or allow some track width adjustment. Worst case I can always go back to the way it was.

 

As you assumed my Z sits quite low and a slight tip of the tube should give me back some of the geometry I am now missing. I could drill the tube and lock it into place if need be.

 

As you stated this raised angle will decrease my track width but I hope to get that back with the 5/8 adjustment in the arm itself.

 

Maybe I can even get a 1/8 more track to allow a bit of insurance room for the ZXT CVs.

 

Once the spindle pins are removed from the old arms tomorrow, I'll install them without springs and go through a complete range of motion experiment before putting it together for real.

 

I'll post pics and my results later this week.

 

Thanks again -