Leaf spring shackles and bushing flex . . .

[mikedc]

Watching an old video of a 2nd-gen Camaro set up for PT:

https://www.youtube.com/watch?v=y0IvH74NqeM

Look how much the lower spring shackle is moving laterally. That seems like a lot. The rear tires look pretty sticky for a street car, but still.

Now I'm wondering how much movement there is with milder street radials. Has anybody else looked into this?

Yeah, I know you can take all the rubber out of the shackles with poly/Delrin. But I like keeping rubber bushings in street cars. Racecars have used wider-top shackles for decades and that seems like a better fix.

[dontlifttoshift]

There is no way I would try to fix an axle lateral location problem by changing bushing material on either end of the leaf springs. The compromises are large, as you already noted, and the gains are minimal.

[mikedc]

I'm thinking of the fact that leaf axles can benefit from a Panhard/Watts bar. Lateral flex is definitely a thing with leafs overall.

I wonder if wider-top shackles would be worth adding on a street car. It wouldn't help as much as a Panhard/Watts but it's a much less severe modification. You would only need to add a longer mounting tube to the subframe rail. (On the old Mopar NASCARs, they left the inner-facing side of the shackle unchanged, and just added all the width to the outer side.)

And of course the benefit would be bigger if the shackles were longer than stock.