Auto-X / Roadrace rear suspension 1969 Valiant

go-fish said
All, good points to consider. Hyperco is the company that I have already contacted. No reply yet but I did the quote sheet they have online.
Preliminary thought is that the spring perches will be at 41-42” spacing (right under the frame rail). The slider will be placed on center of the frame rail and the relocation boxes in the frame will be canted to be in alignment with the toe. What I need to research is how much toe.

The AFCO attachment posted says toe should be 1.5” - 3” in. Right off the bat I am thinking no more than 1.5” for this application (non oval track car). I want to find the proper toe in. Possibly look at the measurements for E-body and see how they compare with the 1.5” - 3” suggestion for oval track setups.

Something that is a recurring ponder is if the spring perches need to be canted in-line with the toe’ed spring. If I come to the conclusion that a lesser toe-in suffices (maybe a 3/4” toe) then I think they would be fine being straight. Thoughts on that?

Yeah I don't think I'd worry too much about the spring perches with that little angle. The E-body 8 3/4 perches aren't angled.

Like anything, I would do some more research on the spring angle. As Peter pointed out, the AFCO instructions are for circle track, which definitely has some differences for desired handling compared to autoX or road racing. You don't want a ton of rear steer response, although a little more resistance to lateral movement would be nice.

But, if the plan is to add a panhard bar, you don't need the springs to be angled since your lateral movement will be limited by the panhard bar. And you don't want to compromise your thrust angle or forward bite too much for autoX, since you'll want to be able to accelerate hard on a short track.

Phreakish said
1.67 degree angle from the E body in @72bluNblu 's post equates to about 1.66" of taper (per side) with a 57" spring (which seems to be E body length). The amount of taper is about .03" per inch: 0.291 at 10" of length.

If you want 1.5" of taper over a 57" spring, the spring toe angle would be 1.507 degrees
If you want 1.5" of taper over a 55" spring (a body), the spring toe angle would be 1.562 degrees

If you are going to attempt to taper the springs at all, I would try to match the relocation box and sliders to the angle of the springs. Doesn't take much angle to subtend some measurable distances.

Nice! Was gonna do that calculation, you beat me to it.

I think if I was going to do this at all, I wouldn't go past the E-body numbers.