Some strut bushing info

Ok, this is against my better judgment but sure, I'll explain again.

First, a heim joint is not a "swivel". As you know a heim joint articulates on a semi-spherical end, which allows a range of movement around that end. Probably the most important aspect of a heim isn't the movement it allows, it's the movement it DOESN'T allow. Namely, a heim does not allow any in/out motion along the axis with the threaded end- the long axis. With an adjustable strut rod, the forward mount is attached directly to the K frame, the heim pivots on a horizontal bolt. The rear mount is bolted directly to the LCA. The fixed length of the strut rod itself can't change because of the way it's attached- The forward mount doesn't move, the heim has no play along the long axis, and the rear end is bolted solidly to the LCA. The only fore/aft movement of the LCA with respect to the K frame is because of the arc that the strut rod can move in. Without the LCA the strut rod can swing freely up and down, and to a lesser extent because of the limits of the heim, toward and away from the frame .But the LCA itself is constrained- it pivots up and down on the LCA pin. The pin is bolted solidly in the K frame, it doesn't move. So other than rotating on the pin, the LCA is well constrained from moving in/out from the frame, the bushing has to be compressed and there's very little room to do that even with rubber, and less compression with poly or delrin. Between the constrained strut rod and the constrained LCA you can't swing the strut rod in/out from the frame any significant distance to create an arc that would move the LCA closer to the K. So, the vertical arc is the only way the strut rods pulls or pushes the LCA.

Note all of that is basically true for a stock strut rod and bushing. The strut rod can pivot around the bushings. Its arc is limited by the resistance of the bushings, and although by itself the strut rod can swing in/out from the frame without the LCA attached it really can't move any more in that direction beyond the small amount of compression of the LCA bushing. The only difference is that the OE rubber strut rod bushings can be compressed along the long axis of the strut rod so the length of the strut rod between the K and LCA can change in that direction. So with the rubber strut rod bushings the LCA can be pushed and pulled fore/aft by the arc of the strut rod as well as the compression of the strut rod bushings along the long axis.

Next up is, how does the strut rod hold the inside of the LCA from moving. Well, where is all of the force applied to the LCA? It's at the lower ball joint, via the wheel loading from the spindle. All the force acting on the LCA starts at the ball joint. So, any fore/aft force acting on the LCA has to be at the ball joint end, period. What is solidly mounted to the LCA only 3" away from the ball joint? The strut rod. So the better question is, how, with all the force acting on the ball joint end, and with a strut rod attached to the LCA only 3" from that, does the inside end of the LCA move fore and aft at all? With the rubber strut rod bushings, the bushings can compress so the LCA can shift forward and back with the compression of the rubber bushing. That movement is completely eliminated by an adjustable strut rod, the heim does not allow motion in that direction. Which brings us to the arc that the strut rod moves in pushing/pulling on the LCA. And here's the deal on that, there's a reason the strut rod isn't perpendicular to the LCA. By being at an angle, the fore/aft movement that's created by the arc is only a component of the change in distance that comes from the arc. So, any push/pull on the LCA from the strut rod is very minimal, because it's not pushing or pulling perpendicular to the LCA, or in the fore/aft direction. It was designed that way exactly for that reason, because we all know that fore/aft movement of the LCA is caster change. Some of that arc is pulling the LCA toward the frame, which is constrained by the LCA pivot and bushing.

And even all of that is somewhat dependent on ride height. Why? Well, because if the strut rod is parallel to the ground at ride height, it's at the center of its arc. Which means it is as long as it will ever be. So when the LCA travels up and down, it doesn't push the LCA back any, it pulls it. The only way that the strut rod pushes back on the LCA is if the ride height is set so the strut rod isn't at the center of its arc at ride height. And that is why suspension geometry is so important for handling. This is my car at ride height. Take a look at the strut rod. The LCA will not move aft away from the LCA pin. If LCA moves fore/aft at all, it will be pulled against the LCA bushing.

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My "**** ********" Challenger has gone over 70k street miles as a daily driver with parts you claim don’t even work. You let me know when any of that drag race only stuff does that. That butchered K of yours wouldn't survive a weekend with the 275/35/18's and 1.12" torsion bars on the front of my car.

And "**** ********?? Buddy you've got issues.



Yes, but OMM doesn't understand or believe that anyone else can't call his personal contact at Napa. He doesn't get that even going into a store doesn't mean that the person at the counter will be able to figure out the cross reference guide that most Napa's don't even carry anymore. Or that the computer lists the wrong single piece bushing for the later strut rods.

And worse yet, he doesn't even know how he got the parts he did. He just got lucky because he has a contact high enough up at Napa to figure out that somewhere in a warehouse there's a pile of old Moog bushings. Moog doesn't even have them at the moment.

You won't get an answer from him, he doesn't have it. He didn't even have the part numbers for the strut rod bushings he was recommending when he started this thread, you figured that out.



not worth my time