t4l

iTrader: (1)

My 1997 LS400 is starting to have some front suspension noise and is going to need a refresh soon. The car is my daily and currently 100% stock. The plan in a couple of years is to put it on air suspension for all the lows while still being a functional driver. The front suspension bushings will be the first phase of the refresh and will happen before the end of this year. While the only information that I can seem to find searching online is to stay away from polyurethane bushings in these cars (especially the strut rod bushing in the front). UCFs seem to be about the only car out there where poly bushings are not highly praised. I am running them in almost every other vehicle I own from sports cars, to drifters, to full size trucks/vans and I have no complaints at all. The LS400 is by far the squishiest softest driving car that I've ever owned, but I would like to firm up the suspension some and make it handle better and be more stable. Common sense would say go with polyurethane bushings to help accomplish this, but all I keep seeing online is to only use OEM. Understandably I am going to lose a bit of the soft/smoothness when I go to air ride anyways.

Question 1: Are polyurethane bushings in these cars actually unbearably stiff and hard compared to most other cars out there? Or are they just too hard for folks that desire and are used to the OEM feel of a barge?


The next issue that I keep coming back to is that once on air ride, the OEM rubber bushings will be forced to flex well past their designed range of motion especially when aired out. likely causing them to fail very quickly because the rubber will tear in the bushings. I've seen this over and over on various vehicles that are on air but the remainder of the suspension is stock. Longevity is fairly important, and since polyurethane bushings are normally a free rotating sleeve inside of the poly bushing, the range of motion in rotational axis is basically unlimited. This seems like a no brainier when it comes to the upper and lower control arm bushings since they will be constantly (and only) moving a large amount in their normal rotational axis. The one I am more concerned about is the strut rod bushing where the arm connects to the frame. UCF20 has this bushing turned 90 degrees and upon movement it will not only rotate on it's normal rotational axis, but also along the axis perpendicular to the normal rotational axis. The stock bushings seem to deflect quite a bit depending on the height of the suspension (for example jacking up the front of the car results in this bushing being flexed quite a bit. The same effect if the car is dropped all the way to the ground). While the polyurethane bushing would likely handle the deflection better than rubber without tearing, I am worried about it being too stiff and putting unneeded stress on the arm, or having other binding issues due to the stiffness.

Question 2: Will the polyurethane bushings in the strut rods be fine with the extra bending due to constant up/down that air ride causes? Or will the stock bushing hold up to this motion just fine without ripping prematurely?

Question 3: Am I completely out of line all together and the car will ride like garbage with polyurethane bushings paired with coilover/airbags? Some of the smoothest riding vehicles I've ridden in were on air bags, but I am unsure of the bushings.


I would like input (especially from people who are on air currently) What are you doing for bushings, and how are they working?

timmy0tool

iTrader: (7)

hello, first I would like to start by stating that most folks here like the factory feel so they will almost always lean towards going with OE rubber bushes for that plush ride that lexus designed and intended. they also don't slam their cars so your audience is very limited here.

with that said, i personally have a 97 on aftermarket air suspension (BC coilovers on UAS bags) and love to park sitting on the exhaust so here is my input. i have stock bushings everywhere even the original strut rods (161k miles). i have not seen any tearing, experience clunks, or have abnormal tire wear (other than the normal wear you get from an air-suspension equipped car, bc i don't have leveling sensors)...yet. i say yet bc as you pointed out certainly i am overexerting the range of the stock bushings as i air up and down daily. to minimize i recommend to unload all bushings when installing the new suspension and clocking/loading them at ride height then tighten them down to spec. this way the bushes are less likely to overstretch. i have not done this so only time will tell when my bushing will fail. also my car has been in California all its life so it never sees snow to be exposed to corrosive road salts so my bushing were generally in good shape to begin with.

as for poly use, it would be a plus to use it for a car with aftermarket air suspension. you will not necessarily "kill" the plush ride but it will definitely tighten things up which is a good thing. bc the stock bushes are so soft, jumping to poly is such a drastic change that people are immediately inclined to dislike it. from what i read on your post, you know the pros and cons of running poly already. i would not worry about adding stress to the arms or binding. my last advise is to make sure they are well lubricated, bc a squeaky suspension is annoying!

dicer

Personally I would think a poly bushing at the bottom of the shock strut would be a win win, since that is too much load for a rubber. And I really don't understand some of the kits for say the UCA pivots, the existing ones are steel spherical joints and people complain that poly there is going to affect the ride? I'd rather the steel though.
Also any time you can tighten up the suspension the alignments are going to stay put, unlike when there is rubber to give.
If you are talking about the lower control arm it needs a bit of give because the diagonal caster strut pulls of pushes on the wheel end of it to adjust the caster angle so it being real ridged is not a good thing.

t4l

iTrader: (1)

Thanks you guys. That is what I was looking for. My upper control arms seem to be fine with no play, so they are going to be left alone for now. I think I'm going to replace the lower control arm bushings, strut rod bushings, and sway bar mount bushings with polyurethane. And replace the end links with new Moog. (Ball joints were just done last year). If I don't like the way it rides, I can always switch back. It's covered by the lifetime alignment at the local Firestone so I can change things up at will and the re-alignment is free.

Thanks again.

Losiracer2

I think its all the old timers on here liking the factory ride of the LS400 that say to retain the rubber bushings. But then again, coming from an NVH perspective, having poly would not dampen all those vibrations as well, so you may be giving up a degree of comfort going that hard.

I would do only the suspension bushings as having had experience with motor mount bushing being poly in my Accord w/ a prelude swap, it definitely isn't the smoothest when sitting at stop lights.