I've heard many people praise poly bushings and I've heard others say they aren't any good for anything but straight-line purposes. I've had them in the coupe for years now along with F40 springs (stock), Carerra shocks and a 1-inch rear sway bar and find my car has no wheel hop and very decent handling. But then I don't exactly autocross the thing. With a G-Tech (so take this with a grain of salt) I measured over .70 G's with this set up using 20 year old P235/14R Eagle GT's, rubber bushings up front and a large 1-1/8 bar up front. This number would probably improve somewhat with poly bushings up front and if I were to lower the car a bit but that's another discussion.

When I set up the car for shows (no rear bar, 3/4-inch front bar, lighter shocks, stock unboxed rear lower arms with rubber bushings but leave in the uppers with poly bushings, tall skinny stock bias ply tires) I still get good straight-line performance with no wheel hop but of course corners suck. Both configurations use the same stock F40 springs and a stock ride height. The car does have the extra braces that tie the front mounts of the rear control arms together.

Anyway, my question is: I hear a lot about rear suspension bind with all poly bushings causing all sorts of problems. In my experience I just don't notice any such problems during "enthusiastic" driving. The car is stable and predictable and can be steered easily with the wheel or the gas pedal. On rough roads or smooth the car never seems to get out of shape handling-wise.

I've heard it said many times that all poly bushings in the rear will cause rear suspension bind which will cause all kinds of handling issues. This is reportedly caused by the inability of poly bushings to deflect like the original rubber bushings.

I also know that polyurethane bushings (the good ones anyway) DO deflect, just not as readily as rubber. They also last longer and are much less suceptible to fatigue which eventually leads to sloppy bushings which can contribute to wheel hop and other malodies.

So I'm left to conclude that: 1. either I don't push my car hard enough to see the "bad" side of poly bushings, OR 2. the polyurathane bushings I have DO deflect enough to allow the suspension to work as designed.

Any insights would be appreciated as I'm very happy with the performance of the set up I have and I plan to duplicate it on my wagon unless there is a compelling reason not to. My decision right now is to decide to install all poly or 6 poly bushings with two rubber bushings in the axle housing. Perhaps I need to consider more drastic changes?

The wagon will also have a lower stance (QA1 coil overs in front and QA1 shocks in back), somewhat stiffer springs and poly up front too with air bags assisting the Hotchkis springs in back and larger more aggressive tires. A big block up front will not help in the weight bias department but that's not a point of discussion at this point (though an aluminum radiator, aluminum water pump, a ministarter and relocating the battery to the back may help unburden the front a bit). It isn't going to be a canyon carver but I do want it to handle well.

I have exactly the same experiences you do. My 'Camino handles quite satisfactorily. I want a fast-ratio steering box, and then I'm done modifying that chassis.

If Poly bushings bind, I haven't seen it as a problem. They DO compress, but have a firmer durometer than the stock rubber ones.

If I had it to do over, I'd install a truck arm kit. At the point where I finally get a Vista Cruiser or Sportwagon, I'll do a truck arm conversion on that chassis. I'm not going to remove my poly bushings/no hop bars/HO Racing springs and swaybar to change over to a truck arm kit, though.

Rich ....... I agree with what your saying ....however for a dedicated drag car ,with high HP and slicks you need the suspension to react quickly and smoothly and poly bushings do not always do that , also poly bushing in a stock type sheetmetal type sleeve can bind easier than a poly bushing in a machined billet alum bushing shell....

I have all poly bushings in my daily driver street car with big sway bars but for my Chevelle they were way to stiff at the track back to new rubber for the front and hybrid poly bushing in billet alluminun shells for the rear... hopefully that will work out better .time will tell FWIW

My car is not a driver yet but I put polyurethane in the front and rubber bushings in the rear because of the same concerns you have.

When I restored the coupe the first time I put all new rubber bushings in the rear and I had no wheel hop. The rest of the suspension set up was exactly as I described above. When I completed the second restoration in 2000 the thing was exactly as I last drove it and I had horrible wheel hop. The rubber bushings had less than 6000 miles on them. They still looked great but obviously weren't doing their job. I don't really understand it as the day I parked it and started the 2nd resto it had no wheel hop, years later but no more miles later it had horrible wheel hop.

After I swapped to polyurethane the wheel hop was gone, it handled as good as before (if it handled better I couldn't feel it) and rode no more harshly than it did with all rubber. I did make a point to follow the directions from Energy Suspension and I liberally used the bushing grease they supplied. I've never heard any squeeks or groans from the suspension which is also a common complaint about polyurethane bushings.

My point is, if you install all rubber, expect to have to refresh the bushings every so often to keep the wheel hop issue at bay. Even bushings with moderate use and age will be worn enough to cause problems, at least in my experience. With a small small block (327) I don't feel the suspension was ever over-abused by excessive horsepower and I never have driven it abusively. Enthusiastically yes, abusively no.

An added thought: I always used Moog bushings, a brand I very much trust, but perhaps there are better rubber bushing available that don't deteriorate from use and time quite so fast?

Rich, my experience is the same as yours. I changed too many variables at one time on mine, so I really don't know how my car would handle with rubber bushings in the rear.

I upgraded to a posi rear (no hop previously with the peg-leg), SSM Lift bars (compared to stock C-arms), Poly Bushings (to replace the 35 year old rubber), and installed an F-41 rear bar all at the same time.

It really handles nicely IMHO, and I plan to run the exact same setup in my new chassis which I do intend to autocross. I wish I could easily compare it to using rubber on the rear uppers, but that's a lot of work just for a comparison.

I also know that polyurethane bushings (the good ones anyway) DO deflect, just not as readily as rubber. They also last longer and are much less suceptible to fatigue which eventually leads to sloppy bushings which can contribute to wheel hop and other malodies.Poly bushings do not deflect, that is their design. Herb Adams is quoted saying "most urethane bushings are so hard they must be considered solid, because they offer little ability to absorb rotational shear within themselves".

So I'm left to conclude that: 1. either I don't push my car hard enough to see the "bad" side of poly bushings, OR 2. the polyurathane bushings I have DO deflect enough to allow the suspension to work as designed. No poly bushing will allow your rear suspension to work as designed so you obviously don't push the car hard enough to see the bad side of poly bushings. :D

So...ummm...What exactly is "rotational shear"?

The way I understand it, rubber bushings are bonded to the inner sleeve, and outer shell. The inner sleeve is bolted solid to the control arm cross shaft (front) or the frame bracket (rear), and is serrated so the sleeve cannot turn (rotate) along with the control arm as the control arm follows the bumps 'n' potholes in the road.

RESULT: The outer shell is rotated by the control arm, the inner sleeve cannot rotate, and so the rubber is deformed elastically as the control arm moves up 'n' down. Rotational shear?

Poly bushings are NOT bonded, in fact they are installed with grease between the poly and the metal sleeve and shell. They do not deform elastically with rotation, and to me that means they have no "rotational shear".

Which means NOTHING when it comes to deforming as a result of suspension loads other than the control arm swinging up 'n' down. They still deflect or deform with suspension movement, (I think this is called "compliance") although perhaps not as much as softer rubber bushings.

Herb Adams theory on front suspension is that he doesn't like sway bars because they interfere with the independant action of the front suspension. So instead, he recommends mega-stiff front springs that interfere with ANY action of the front suspension. You gotta take him with a grain of salt...

Poly bushings have very little to do with any of the properties involved with things like "compliance" or "deflection". They simply are the last step toward a solid link. BTW, are we not talking about using them in the rear suspension where the bushings required characteristics are totally different than in the front?

The "theory" as you put it on front suspension action being limited by the sta-bar is less of a theory and more like an accepted and proven fact in the motorsports arena. Vehicles will always handle better with a stiffer spring and smaller sta-bar. Want proof, swap in bigger springs and less bar then do some road course events, then swap back and compare track times. Better yet, how about a little side bet. My Elco the way it sits (I drive it to work everyday/only car) against ANY "A" body you have access to.....we'll run them on the road course and compare lap times. BTW, I have NO sta-bar and NO poly bushings anywhere on my ride.

Theories are nice to have but once they have been disproved time and time again it just old rehashing them. No respected auto-x or road course car is going to have poly bushings in a location that requires more than one plane of movement. Most competitive cars won’t have them anywhere. On a street car they work fine in the front arm location, sta-bar or possibly in a rear leaf spring eye.

Some builders prefer a softer spring and a bigger bar/some prefer a larger spring and smaller bar. In any case the sta-bar is only used as tuning tool to fine tune the way the car reacts to roll. It is important to remember that these builders are not referring to say a car with a 200lbs spring and a 1.250 bar vs. a 900lbs spring and a .500 bar. It is more like 600lbs vs. 900lbs and 1.00 vs. 1.125. A couple hundred pounds of springs makes a huge difference, heck in the rear I experiment with as little as 25lbs of rate.

Back to the topic originally asked, poly bushings are a good compromise to solid/Teflon bushings when used in location that only require rotation (sta-bar, front control arm, rear leaf, rear sta-bar) or for use in a compression environment such as a body mount. In a location such as the rear control arm where the bushings is required to not only rotate but also deflect and allow the arms to “shrink” or “grow” as the need rises requires the use of a spherical bearing or rubber joint. How could have any understanding of suspension geometry and how it works and then argue that bushings that inhibit articulation are "good". Do auto manufactures like that fact, no. It means giving up ride comfort and "cruiser" ride characteristics in order to handle properly.

The front control arms move much like your elbow, just up/down. It cannot twist without severely binding (and pain). The rear arms move similar to your wrist. At any given time they may be right/left and up/down at the same time. Does this help at all?

Hey Dennis, how many times have you taken the elco to the roadcourse? was this before the stiff spring thing?

That does help Dennis but I do have to disagree with you concerning polyurethane bushings not having any deflection in them.

I have poly bushings in the rear of the coupe, I installed them myself. They are only slightly more stiff than brand new rubber bushings. Perhaps there are more than one kind of polyurethane bushings out there but the kind I've used (Energy Suspension's Hyper-Flex) do deflect. Unlike rubber, however, they do return to their original shape for a much longer period of time. They are NOT like the old hard nylon-like bushings that were available when poly bushings first hit the market which I suppose are still available from some companies.

I swap the rear lower control arms in this car 1 or 2 times a year (switching from show configuration to cruise configuration) so I see first hand how the rubber and poly bushings differ both during installation and in driving. They really aren't that different in either respect.

In short, the polyurethane bushings I'm using, while noticeably stiffer than rubber, are NOT close to being a solid bushing. I wish someone could publish some deflection measurements comparing these poly bushings to rubber but as yet I've not found anything with hard numbers to them.

I will take Herm Adams with a grain of salt since his ideas may work great on perfectly paved race tracks or well maintained roads in sunny climates, but in the real world of winter ravaged pavement I live in an ultra-stiff suspension is not condusive to keeping the car in one piece for very long. Nor is it condusive to keeping the car in contact with the road since when severe road surface imperfections such as potholes, frost heaves and the like are encountered a very stiff suspension tends to lift or drop the entire car instead of allowing the wheel(s) to ride into or over the obstacle. Somewhat softer springs can keep the tire in contact with the road more consistantly. There's a balance in there somewhere between soft and stiff but I've tried very stiff and it doesn't work well in my applications.

We did a '69 Chevelle front and back with nothing but positive results, other that some squeaks. For the el Camino that I am doing, I drilled the bushings and added grease fittings. The kit I got had grease with it and the bushings aren't meant to be run dry. I also welded lugs to the frame to keep the bolts from turning. If the bolts gets stuck in the bushing, the holes in the frame wouldn't last long.
This is just a regular street car and the bushings took all the wallow out of the handling. With normal street driving, the suspension isn't moving enough to ever have a binding problem. We needed new bushings and they were cheaper than the factory stuff. For us they work fine. For racing, you guys know best. Advertising sure does sell lots of junk though.

I will concede that in a harsh driving environment running ultra stiff springs may not be the most driver friendly choice, although going from 350's to 750 actually improved the ride in my case and would provide similar results in most cases. Increasing front spring rate does not affect NVH nearing as much as one would think. Typically the rear rate when properly matched to the front frequency will determine how the vehicle will ride.

It may possible that you are running a "softer" poly bushing. It does not change the characteristics of polyurethane and it's resistance to compression which makes it a very poor choice for use in converging 4-link suspensions. Driving impressions are not a valid argument for whether or not they work. Track results will show that car will actually be faster with a good rubber bushing than a poly bushing.

No Cody, missed Willows last weekend and next track day isn't until March. I'll be sure and post results from the event though. Previous track with old set-up was limited to auto-x, but because I drive it everyday (and hard) I can get a pretty good feel for how it will respond come track day.

What do you mean by "drilled the bushings" ?

Do you drill a bunch of small holes in the poly part of the bushing itself to allow it to deflect??? I have some "extra" bushings that I wouldn't mind experimenting with, because I bought a kit for the rear, and only used the uppers because the SSM bars use their own bushing.

I do want to autocross this car, but I drive the car a lot, and have noticed my rubber front bushings that I installed 4 years ago are getting pretty worn out already.

oops, read it again... drilled for greasing purposes graemlins/clonk.gif

"Want proof, swap in bigger springs and less bar then do some road course events, then swap back and compare track times. Better yet, how about a little side bet. My Elco the way it sits (I drive it to work everyday/only car) against ANY "A" body you have access to.....we'll run them on the road course and compare lap times. BTW, I have NO sta-bar and NO poly bushings anywhere on my ride."

If you actually haven't had it to the track then how do you know what works better? There are a LOT of guys using soft springs and bigger sway bar. It is just like anything else; got to have a good driver and the car has to be tuned to the setup correctly. There are just different ways of doing things. I personally like something righ intbetween. I think Hothckis has a pretty good setup that lays right inbetween, using a hollow swaybar and a 600ilb spring. Although i too might want to step up the spring rate, hopefully reducing bottoming out, although that might be more on the shock rather than the spring? Other than the above comment about the small bar stiff spring, Dennis's comments on the poly thing are pretty much on the money. I used to think they were the hot thing, just like Be-cool radiators and Demon carburetors...Advertising at its best!!

Statement above based on lots of time with other peoples cars. Let me contact them to see if they kept a running progress of their set-ups. I have personally been involved with 3 very high speed track cars that have all done very well stepping up the spring and down the sta-bar. These are track cars with very little street time so things like potholes and uneven road surfaces do not play into set-up selection.