WHY DO WE UPGRADE OUR SUSPENSION
LOWER CONTROL ARM BUSHINGS: Some get concerned about the arm sliding off the bushing. To prevent this, the T bar must be pushed all the way forward during installation. They usually stay put unless another force is acting on them.
STRUT RODS: The technical term is brake reaction support which is its job. Keep the lower arms in line when braking forces are driving them backward.
Peter, I agree with pretty much everything you've said here. I would like to clean up a couple things you said though.
First, the torsion bar thing. This doesn't make sense, and it's easy to explain why pushing the torsion bars all the way forward isn't necessary.
If you assume that the LCA socket can't
move on the hex end of the torsion bar, then the torsion bar doesn't need to be bottomed out in the LCA socket to keep the LCA from moving back. If you assume the opposite, that the LCA can
in fact move on the hex end of the torsion bar, then the reverse is also true- the torsion bar can move in the socket. Which would also mean it can move in the crossmember anchor, so the torsion bar can't be assumed to be holding the LCA from moving back. Either way, there's no reason to bottom out the torsion bars all the way forward. If they can't move then the LCA can't slide back, and if they can move it doesn't help.
Second, the strut rod thing. Yes, the strut rod is a "brake reaction support" and that is its primary reason for being there. Because they are basically a solid link, especially with an adjustable strut rod, they prevent motion in both directions, both forward and back. So they will keep the LCA from sliding back off the LCA pivot if you have a poly or Delrin bushing, just like the originals kept the LCA from walking back and tearing the rubber bushing at that location.
i would disagree with the comments on lower control arm bushings.Most i've dealt with last years and yearsThey are hard vulcanized rubber and when installed properly and tightened at ride height offer some torsional resistance to lower A arm travel and can be plenty firm.The poly or or hard plastic is avoided by many the second time around...i've seen that plastic crack and distort after only a couple of years.
I have never had any problem getting enough caster on the front end when rebuilt with new bushings..maybe i've been lucky.
I don't auto cross.
People have "issues" with the poly bushings because they install and maintain them like they're rubber bushings. They are not. With the OE LCA bushings there are no surfaces that slide on each other, the motion of the suspension is just the flex in the rubber (which is built in binding at the extremes of suspension travel, BTW). So there is no need to lubricate the OE bushings, and no way to do so. With a Poly LCA bushing, the bushing actually rotates on the LCA pivot pin. So you have two surfaces sliding on each other, which requires lubrication. And it requires re-lubrication. That's why people complain about the poly bushings squeaking. Well, if they're squeaking it means you need to lubricate them. And if you don't, they will fail. This is no different than any part that requires lubrication. If your ball joints started squeaking you'd lube them, and if you didn't do that immediately they'd wear rapidly and fail.
The other change from OE is that the poly has less flexibility. That's the improvement, but it also has consequences. Namely, the fit of the bushing on the LCA pivot pin, and into the existing LCA outer bushing shell (depending on which poly bushing you're using) has to be tight. These parts have to be a tight slip fit. If there is any play, the bushings will wear out prematurely. Because people install the bare poly bushings into old outer bushing shells and onto original LCA pivot pins with the inner shells the fit is not always what it needs to be. And guys assume the bushings "just slide in" and it doesn't matter. Well, that fit is very important. If you went to install an OE rubber bushing and the pivot pin was loose in the inner shell you wouldn't install it. Same with a poly bushing. No, it isn't a press fit, but the fit still has to be correct.
If you install the poly bushings correctly- lubricate them and make sure they have the proper fit, they'll outlast rubber every time. I always use greaseable LCA pivot pins with poly bushings. They fit the bushings with a higher accuracy than the OE pins, and you can lubricated the bushings as needed. The small grease hole is negligible for the strength of the pin, and the greaseable pins from Firm Feel are a higher quality than the OE pins were to begin with.
If you use Peter's Delrin bushings (I do, they're awesome), the fit is even MORE important because the Delrin has less give than even the poly. So the pivot pin tolerance must be exact. I tried three different pairs of original pivot pins with mine, none fit correctly and all three pairs of original A-body pivot pins and inner shells had different diameter measurements. That tolerance is critical with harder bushings, they must be a tight slip fit with no play.
I don't know why you guys have problems with rubber bushings..they last years and years.
If you don't tighten your suspension at ride height you will ruin them because you are keeping the rubber permanently twisted...and then you will be blaming the off shore supply.
Rusty,be careful with rear sway bars.I have read that they are not always a good idea.
The OE rubber bushing quality is abysmal now. There are several threads about them not even fitting into the LCA's or onto the pivot pins. None of them will last like they used to, even with proper care. The quality just isn't there. Here are a couple threads where multiple different members talk about Moog and other brand OE style bushings not fitting.
LCA pivot pin loose in bushing problem
Lca bushing help.
Lower control arm bushing
As for the rear sway bar, that depends entirely on how your car is set up. From the factory the front's were undersprung and the rears were ok, but if you do something like add SS springs out back then the rear end is very stiff and adding a rear sway bar makes that worse. If you upgrade the front suspension and have the proper rate rear leaf springs a rear sway bar can be very beneficial. It's not a matter of "rear sway bars are not a good idea". Like any suspension upgrade you have to consider the whole suspension system, some need rear sway bars, others won't, it depends on set up.