poly vs rubber

getting ready to finally redo the suspension in my Classic 900 and I wanted the low down on how uncomfortible poly bushings can make a car.

I have my ti fully polybushed.. but it is also on a rockhard Bilstien pss9 coilover system.. what I am doing to the saab is a set of lowering springs, 16inch rims, and some sort of "sport" shock that is not a bilstien.. this is not a race car, I want it to be semi-comfy to drive for long distances.. but still be able to handle well.

Should I just replace the worn out bushings with more stock.. or should I go with the poly?

I am biased against poly bushings that will see any kind of rotation. Especially after I saw the oem e30 suspension bushings. Those things are substantial in my humble opinion.

I'd say it really depends on what the oem bits are like. Some OEM bushings are very very soft.

Remember that with poly the metal sleeve actually rotates inside the poly bushing. That means that if there is a lot of friction in there, and if it's at a point of high rotation (like a trailing arm bushing), the bushing may load the suspension in the compressed 'direction' slightly when going from a compressed to static state. Rubber bushings are made to twist and flex so they always unloaded at 'rest'. Not only that, but this constant friction can cause them to oval out and then you have real free play. Like, jiggling in place free play. Not just tired bushing deflection like you get with rubber.

That's why you're supposed to tighten up sway bars with the car on all fours. Otherwise you'd have bushing preload.

I've got full poly bushings in my 2002, but like your 318ti, it has a pretty stiff Bilstein suspension and is not a DD. I don't mind it in that car, but for a daily it would be a bit much for me.

I think the best compromise would be to use rubber for all the suspension arms (I'm not familiar with the Saab C900 suspension, so I can't be more specific) and poly for the sway bar mounts and end links. You'll get good damping but crisp transitions. Plus, the sway bar bushings should be easier to replace should they wear prematurely.

The first thing I did on my B13 Sentra was bushings - including the big honking one in the rear that you're not supposed to change because it binds something fierce if you do (springs and shocks were changed later). The original rubber had about 50,000 miles on it when I changed them.

I had the car for another 100,000 miles with the poly and It rode like it had about 10psi extra in the tires, squeaked something awful the closer it got to freezing outside, and I usually took the front apart and re-greased the bushings every year (they squeaked the worst). I ~never~ re-greased the rear bushings, even after 5 years of street/winter/autocross driving. I'd do it again.

I replaced all the bushings on my Nissan Hardbody a couple years ago with polyurethane. The original rubber had about 170,000 miles on them. Marginally noticeable difference. The springs and shocks are all still stock. They don't seem to squeak at all, or maybe the ambient noise of "truck" is just too much....

To add onto what skinnyg said, a few people have been known to add zerks to the 'bushing race' I suppose you could call it. Then you can grease them with a grease gun in a matter of minutes.

I've always wanted to try a spherical bearing that was pressed into a poly bushing. Sounds crazy I know, but I still would like to try to make one someday.

I am running poly in my ti on the front and rear control arms. Subframe is stock rubber(diff mount is rubber Mcoupe) . I went with H&Rs and tokico blues and the ride is very comfortable. I drive it 150 miles a day. No squeaks.

My Country Squire is all poly. Including the bodymounts. No squeaks from the bushings....but the ride is harsh because of the bodymounts.

My protege with 275K mile suspension is still tighter and feels better than the ti with all new upgraded parts.

So, It really depends on the original design of the bushings.
See how bad the stockers are, for the milage it has and decide from there. I also agree poly for the sways/endlinks even if you go rubber on the rest.

I've never heard that sways need to be tightened on the ground, but definitely for rubber control arm bushings. The inner sleeve on most are knurled or have teeth that grab the mount to keep the sleeve from turning since it's bonded to the rubber. This was actually a issue with my wagon with the shaft uppers. The nuts were backing off because the ES inner collar would force the washer and nut to back off when the bushing/control arm moved.

If the car is going to see track time Poly is the minimum upgrade I would do. There is no way to locate your control arms etc, in any sort of tunable fashion without decent bushings.

Regreasing annually is essential and some cars need to be considered for bind up issues like the 1st Gen RX7 upper rear control arms.

Now for a road car it doesn't bother me but its not necessary in most cases.

My 0.02c

ok.. so I guess it is stock rubber for the front a-arms and the trailing and forward links on the rear and poly for the sways.

I just wanted to do the work while the engine is out and since I am swapping the suspension from early to late. Staying with rubber cheapens the budget

Oh, another thing to consider is if the poly bushings are split you can often install them by hand.

Rubber usually needs to be pressed in

Taiden wrote: Oh, another thing to consider is if the poly bushings are split you can often install them by hand. Rubber usually needs to be pressed in

And if it's like ford, you bend up the arms pressing the rubber in/out.

I don't use poly in anything that rotates. Body mount types of applications I've had no problems with as long as they're greased well when installed. Here's a bud of mine who had polys on control arms. http://www.youtube.com/watch?v=QwlofW23Jyk

The last go-round on my Nissan Hardbody I re-greased them with Moly Slip. The squeaking hasn't come back that I noticed yet. I've also used Super Lube, Nev-R-Seize and regular grease. I ~did~ run Zerk fittings in my old Sentra, but the fit was so tight that I just couldn't pump grease in there - colossal waste of time. YMMV.

Aren't there different degree's of poly bushings? When I rebuilt my Opel GT's front suspension I had a choice between OEM rubber, urathane and polyurathane. I chose urathane and have been very satisfied, no squeaks and not harsh. The polyurathane was recommended for track cars and could be harsh and squeaky

I installed urethane everything in the front of my Dakota Sport V6, years ago. The transformation was shocking - It became a fully hoonable pickup truck. The ride wasn't worsened in any meaningful sense.

When I disassembled and fixed+improved everything all at once on my NA Miata 2 years ago, I installed the full Energy urethane kit, which is like 217 pieces. It's a chore to do it all, but - in conjunction w/ the FM 1.5 suspension, various braces and new bearings all around, the car feel amazing. It's firm, not hot harsh. I used copious synthetic grease and there are no squeeks at all.

My my has Powerflex purple in the main 4 of the subframe and the front control arm to "lollipop" locations. The car didn't seem any more harsh afterward, but it's mighty hard already.

I like that urethane is something I'll do once on a car, and that it's not degrading again as soon as I put the car back on the ground after doing the work.

I blame compliance for the sake of comfort as the trigger for the decline of western civilization. Compromising the one thing a vehicle is supposed to do well was the beginning of the end.

-- The Partnership for a Solid Bushing America

On a c900, in my experience, there is no real reason to install poly control arm bushings on a street car. Also, if the control arm bushings aren't cracked and obviously failing, you might not even notice the difference between old and new rubber bushings (I didn't when I replaced a set on a c900 w/150k on the clock). (Exception: inspect the RH upper a-arm bushings, which get exposed to exhaust heat and degrade.) I would bet you a nickel that if you replaced the lower spring seat bushing you won't be able to tell the difference: they almost never go bad.

When installing new bushings, see the Bentley manual to set the attachment brackets up at the right angle.

Regarding compliance on these cars: the upper bushings are fairly thin: there's not a whole lot of rubber to deflect to begin with. Not sure about the lowers, but they don't seem too terribly large, either.

For a street-driven car, again, in my experience, poly outer AND INNER swaybar bushings make a big difference and are worth installing. The outers come in black and red poly -- the red type aren't durable and crack. Inners are available from www.sasab.com, and outers from just about anywhere. Lubricate them all with anti-seize goop, or just let your PS system leak on the inners.

I would inspect the rear upper links for degraded bushings, and replace, if necessary; they commonly rot. I'd also consider replacing the panhard bushings. The rear lower control arm bushings seem to last a good long time.

I've read that rear poly swaybar bushings are nice to have but they're $$$.

If you are in this for the long haul, avoid Scantech rubber bushings and look for Boge-branded stuff (Boge was OE supplier). That said, Boge doesn't make all of the bushings anymore and you may have to settle for Scantech.

The only performance non-Bilstein shocks I'm aware of are Konis and KYBs. The KYBs are not my cup of tea: too stiff in compression. Cheap, though.

Regarding poly bushings on c900 shocks: I've tried 'em and found that the constant pounding ovalizes the lowers; I just stick to the rubber stuff as a result.

And while I'm vomiting out all of this E36 M3, the front lower shock mounts are pretty easily stripped, so be gentle down there: strip one and you're likely going to be looking for another a-arm.

You may have to grind down an open-end wrench to get the dual-nut uppers off, if the original, somewhat thin nuts are used.

Don't forget to add some camber while you're at it.

Taiden wrote: I am biased against poly bushings that will see any kind of rotation. Especially after I saw the oem e30 suspension bushings. Those things are substantial in my humble opinion. I'd say it really depends on what the oem bits are like. Some OEM bushings are very very soft. Remember that with poly the metal sleeve actually rotates inside the poly bushing. That means that if there is a lot of friction in there, and if it's at a point of high rotation (like a trailing arm bushing), the bushing may load the suspension in the compressed 'direction' slightly when going from a compressed to static state. Rubber bushings are made to twist and flex so they always unloaded at 'rest'. Not only that, but this constant friction can cause them to oval out and then you have real free play. Like, jiggling in place free play. Not just tired bushing deflection like you get with rubber. That's why you're supposed to tighten up sway bars with the car on all fours. Otherwise you'd have bushing preload.

My experience as well.

For a street car, I'd just go oem rubber type.

this was a mostly "while I have the suspension out for replacement" thing. Thanks Procaine, I will stick with the rubber for all but the sways.

My experience is that poly isn't even really an option. I put some on my Impala SS and hated them. They were noisy two weeks after you greased them and they wore themselves out to the point where they were just gone. IMHO, they have way more drawbacks than benefits. In the future, my only two options will be rubber or Delrin.

Solution.

I just realized that I have access to the tools to make those.

I'd be tempted to use circlips instead of tack welds though

Taiden wrote: I just realized that I have access to the tools to make those. I'd be tempted to use circlips instead of tack welds though

Cool. I'll be bugging you over the winter to have some made up for the Celica. Those are for the Escort, so that's covered.

I swapped a full set into my AE86 SR5, and they were fantastic. Nicely firmed things up, though it did increase interior noise a good bit.

That being said, i'd never do full polys in the Mustang. Just asking for too much bind.

Why not use Delrin?

I want to use those "johnny joints" for my next build.