Rubber or Poly for a Daily Driven Corner Carving Street Machine?
Poly LCA bushings are not locked in position like Rubber. They can float forward and backwards. Noticed this when driving the 67 in reverse. That said it, probably has 100K on the rebuild. They are noisy. I'll be rebuilding the front end this spring. Moog rubber LCA bushings, Firm Feel upper control arms, Bilsteins all around, 76 cop car front and rear sway bars, Rubber everywhere except the sway bar links. I've also tried the graphite impregnated bushings and they are just a little bit better. On a daily driver Poly bushings are way too annoying for me. I love working on cars, but hate having to work on them.
To say that the rubber LCA bushings are "locked in" is a bit of a misnomer. Yes, the bushing shell is pressed in, and yes, the LCA pin is pressed into the insert in the bushing. But the only thing that holds the bushing to the shell, or the insert into the bushing, is the bonding of the rubber. Sure, it's more resistance than the poly LCA bushings, but the rubber can and does separate from both the insert and the shell. That's what happens if you torque the LCA pin nut with the suspension at something other than ride height, and obviously as the rubber wears out.
That said, the LCA pin can slide in and out of the poly bushings. But it's not the job of the LCA bushing to locate the LCA fore/aft. That's the job of the strut rod. If the strut rods are the correct length, the LCA, pin, and bushing don't go anywhere, even with poly LCA bushings. The stock strut rods are a "one size fits most" kind of thing, and what that really means is they don't fit anything all that well, just "good enough" to get the old factory alignment (which isn't what you want anymore!). I have adjustable strut rods on all of my cars, and none of them are the exact same length as the stockers.
I think the adjustable strut rods are the way to go anyway, but if you use poly LCA bushings I think they're more important, especially because the aftermarket strut rod bushings are kind of questionable in their tolerances. Same with the greaseable LCA pins- they aren't mandatory, but they sure do make life easier. The poly LCA bushings aren't the same as the stock bushings, so using them with all of the stock components isn't necessarily the best practice. When you upgrade your cam you have to install new lifters,valve springs, and sometimes that means machining the heads, new pushrods, etc. Same idea, you have to match everything up if you want your new parts to work their best.
For a car that's primary use is on the street the rubber LCA bushings will be fine. The amount of deflection in the original bushings is pretty small. Sure, it's on an important component, and I think the harder LCA bushings are a great thing. But on a street car they aren't necessary, the difference is small. And you can run poly bushings everywhere else without adding any additional new components, the LCA bushings are unique in that respect that you should really upgrade the strut rods and pins too.
