Please delineate the Slop, movement and flex you are referring to above.
I'm not seeing it, or that it has any appreciable negative effects you note, if any
Do we agree the TB end of the LCA's main task is to transfer rotation/lever arm forces to the TB, and since braking forces (when moving forward) acting thru the LCA are redirected to the rear by the resistance of strut rod, and those forces are reduced by ratio distance of the strut connection to the BJ to the distance of the strut to the TB pivot point, in an opposite direction?
In most situations, if not nearly all, the BJ end of the LCA is being forced/loaded rearwards, the TB end of the LCA is the direct opposite direction with reduced force, by the action of the strut LCA connection being a pivot point.
It's hard to imagine when those forces would ever reverse, and using up any inherent slop in the design, that would effect handling.
Additionally, there has to be slop somewhere in the TB typical Mopar IFS, in that the LCA and the Strut are in conflicting arcs, and suspension bind would result if totally eliminated.
But regardless, I am all ears.
Sure, if you’re drawing a force diagram it’s really easy, you have the rotational force at the LCA socket acting on the torsion bar, the suspension input at the lower ball joint and the constraint from the strut rod. Easy, simple, and not the whole story.
Just drawing that diagram assumes the LCA is completely rigid. If you’re just calculating forces that’s a decent assumption, it won’t change the total force numbers and it’s why those assumptions get made for the calculations. But if you’re measuring alignment changes in the suspension while it’s under load it’s a terrible assumption, because the LCA is not absolutely rigid (nothing is, but especially not the factory LCA).
The reality of it is that the LCA flexes forward and backwards. It twists, because it’s dimensional and the suspension forces act at multiple points (ball joint, strut rod mount, sway bar mount, shock mount, pivot socket, torsion bar adjuster). Sure, most of those are short levers but just the car sitting on its wheels is an 800+ lb load on the LCA, forget moving at speed, braking, turning, etc. And a lot of those cancel out, which again, is great in a force diagram. But they’re not point loads, they don’t all line up, and because the LCA has dimensions it means those loads twist and torque that arm. The slop between the socket/pivot and arm will allow the ball joint to move around, the big sloppy rubber strut rod bushing lets the whole assembly shift forward/back, twist, etc. And the better the tire you put up front, the more that happens.
This isn’t my video, but it shows the movement at the strut rod with rubber bushings. If you focus on the head of the strut rod, you can see how much it moves. Well the other end is a solid connection to the LCA, so every movement at the end of the strut rod is coming from movement at the LCA.
Was a lot of that slop between the pivot and LCA body baked in from the factory? I bet a lot of it was. And yeah, with bias ply tires and big soft rubber bushings that’s probably fine, for 1970’s handling. Start improving performance, and therefore suspension loads, and that slop lets the car wallow around and leads to vague steering/suspensions responses.
As far as binding, I have Delrin LCA bushings and adjustable strut rods. If you set the length of the strut rod correctly there’s no binding within the range of travel of the suspension. The different arcs all line up well enough before they diverge that you can tune the binding out and match that up with the suspension travel range, since you’re only talking about ~5” to 5.5” of travel anyway.
