I think the only good way to fix this problem (though I have my doubts as to how much of an impact that it has when driving) is to go with a C5/C6 style multi-link rear end with heim joints in order to minimize any change in toe as the wheel moves up and down. You're going to need a custom hub and at least five links per side (not counting the halfshaft), along with custom halfshafts with sliding sections or CV joints to keep the deflection in check.
Thats not at all what I'm talking about. Your "solution" to toe control in a C3 is changing the entire rear to a C5/6? Good luck with that, let me know when your done!
I'm not planning to do it. However, I'm thinking of this from the physics involved - if the rear wheel is on a trailing arm that's fixed at the front, and has no ability to move in and out to stay in a plane with that front fixed point on the trailing arm, it's going to move in an arc - and when it does, the total toe is going to change. As the tire moves in the arc around the differential, held by a fixed front point, the angle of the tire is going to change. This is why they went to a multilink setup starting with the C4 (there's a nice discussion of this in
Corvette From the Inside). In order to keep the toe change minimized, there would need to be another link added above the halfshaft and the center point would have to have the ability to move in and out in relation to the differential in order to keep the wheel in the same plane as much as possible.
It would be a fun project, but I'm happy with the handling of my car with the aircraft-grade spherical bearings up front and VB&P dual-mount rear spring in back. It's not a Ferarri, but it handles well.
Using a stock-style trailing arm, you're going to have some toe deflection no matter what you do.
This is not true at all. What is "toe deflection"?[/QUOTE]
The stock setup using the halfshaft as the upper suspension link combined with a long trailing arm with a fixed pivot at the front is going to cause the wheel to move in a combination of two arcs as it moves up and down (essentially along part of the face of a sphere, if my mental model is accurate). There isn't any way around it without some significant redesign. IMHO, replacement halfshafts with CV joints and some additional bracketry for an upper link would be the simplest solution, though I have no idea why no one has ever come up with one. The more radical aftermarket suspension kits seem to favor six-link setups similar to the C5/C6 design. The C4 was an improvement over the C3, but the engineers realized that it still had some toe control issues. TT's floating T/A would also work, but IMHO would require about as much effort as a multi-link, and quite possibly more frame and body mods.
"Toe deflection" was just how I thought to describe the change in total toe as the wheel moves along its two arcs. Maybe not the most technical term, but descriptive. The amount of total toe deflects from the resting alignment shop setting as the wheel moves.
