spastic rear suspension
What point? You completely missed the point.
The original rear suspension on these cars was designed for use with bias ply tires, which have even softer sidewalls than the radials that everyone runs without bothering to change the OE springs. And that would be relevant IF the OP was using stock suspension.
But he's not. He's using Hotchkis springs that were designed to be used with modern tires, and have different spring rates and leaf construction than the OE springs. They were intended to be used with the tires like what the OP is using, and therefore the "low profile" tires aren't the problem.
The fact that the Hotchkis springs were designed for use with a rear sway bar, on the other hand, could be an issue.
Leaf springs have rate,and bias,they do not know nor care whether you have
mounted bias or radial nor 75 or 40 series tires. What they do know is that they are
either stiffer,resisting motion at a given load ,or softer offering less resistance to that
motion.More resistance means motion transferred to the(in our case unibody)for a
given impact,necessitating more rebound distance to regain contact w/the road,or..
TRACTION. A tall compliant tire regardless of construction will transfer less motion to
said spring,which in turn will transfer less to the chassis, and will always do less of the
"dance". No doubt a rear bar will help suppress and recover the axles roll,and again,
I have a feeling the shocks may have too much resistance in rebound. I believe the OE
skins on My swinger were D75-14's and my fading memory says the sticker said 26psi.
That will absorb a lot of manhole cover my friends. After adding a few leaves, a 3/4"bar
& I believe they were 215/55VR15 potenza somethings(lol,whatever they had late '80's
early '90's) My swinger would "step out" more regularly for sure,but cornered great all
in all. Shocks however, were routinely marketed in the early '80's up till it was a moot
point,as "radial tuned" precisely because of the difference in the tires effect on the
suspension. Modern low-pro gummies are better and more accommodating than ever,
but a W-Y rated 245/40 vs a 175/75r14 over a manhole cover? C'mon man........
