No, it can't be extreme, not with anything even mildly resembling the torsion bar suspension. The Chrysler engineers did a lot of work to make sure that changing the caster didn't create some awful bump steer issue, and I would bet they did a better job than they even knew.
You know why? Because I've run everything from bone stock factory suspension, steering and alignments all the up to what I've got on my Duster now- lowered 2", SPC UCA's , tubular LCA's, FMJ spindles, altered suspension travel, -1° camber, +6.5° caster, the works. And from bone stock all the way up to +8° of caster there was no adjustment that made the bump steer on my Duster even noticeable.
There has been literally 1 thing I've done to a Mopar that resulted in a noticeable (but not significant) amount of bump steer. And that was when I put 2" drop spindles on my Challenger. The resulting control arm angles and steering arm length added bump steer, and enough that I was able to detect it while pushing the car on rougher mountain roads. Not enough to be sketchy, but enough to notice. But that was before I did a deep dive on the Mopar suspension and realized that the drop spindles are in fact unnecessary, because with proper upgrades you can lower the car just as much with factory or FMJ spindles and the resulting geometry is actually BETTER than what the factory set the car up with, because of the bias ply to radial tire alignment changes. I had a contact at the time with a suspension geometry program and we ran the numbers on my Challenger lowered 2" with stock spindles and lowered with 2" drop spindles and determined the bump steer was better with the factory spindles, even lowered 2" and running +5° of caster (best I could get with the components at the time). The bump steer with the 2" drop spindles wasn't crazy either, but it was more than "good practice" and I could actually feel it pushing the car in the right (or wrong I suppose) conditions.
So, if you want to preach about how running around with +6.5° of caster is gonna add bump steer, show me the numbers. Because I run my car that way, I drive it on bumpy mountain roads at a very spirited pace more frequently than I probably should or should admit, and I know what bump steer actually feels like. Maybe the bump steer on my car isn't perfect, but I've literally done nothing to tune the bump steer on my car which is a luxury most muscle car owners don't get. And the only reason I haven't measured and plotted it all out is because it's never been an issue in the real world. So the gloom and doom about bump steer with the torsion bar suspension is 100% unwarranted until you show me numbers that say otherwise.
Lol. C'mon man, that's about as misleading as you can be.
From a technical standpoint, of course it doesn't matter to the toe change what kind of spring is used. But the fact that you change the length of the steering arms, the location of the steering arms and the entire spindle changes literally everything there is about the toe curve.
Saying it doesn't matter if it's a coil over or a torsion bar when you've changed spindles and gone front steer is just flat out silly, the type of spring is irrelevant but everything else that was changed is not.
I fail to see what trying to run the stock mopar spindles with the steering arms flipped to the front for a rack has to do with anything. It's a stupid drag racer trick that results in piss poor Ackerman, everyone knows this and no one with more than a handful of brain cells would do that for a street or handling car. It's well documented poor practice and you can look up a dozen threads on here where I've told people if they absolutely need to have a rack the only way to do it right is with a full coil over conversion. Personally I'm of the opinion that no one needs a rack and pinion to begin with, but that's just my opinion and I know what that's worth.
Sorry @racerjoe, I'll try and follow more quietly as I'm interested to see what it really takes to optimize the coil over suspension for handling, there's far too many people that just slap them on without actually working through the geometry.
