Polyurethane Control Arm Bushings

[Thomas F.]

Sorry if this discussion has taken place previously. If so I did not find it. I am in the process of replacing the control arm bushings on my 69 Vette. I am leaning on using polyurethane bushings. However just about every article I read on this installation says it is more difficult to install than stock rubber bushings. Not that they are harder to press in, but they just take a little more time to install properly. As I understand the articles it may be necessary to modify the inner sleeves by shortening them to eliminate any unwanted movement forward and backward of the A-arms. Also I understand that the rubber bushings do not move, the rubber just flexes as the A-arms go up and down. The poly bushings actually turn on the inner sleeve. The inner sleeve does not turn on the shaft because it is a tight fit and is held in place by the large washer and bolt. If properly installed the the large washer will not press against the bushing but only the inner sleeve. The spacing is critical between the large washer and the bushing itself. If properly installed they will not squeek. I have seen drawings showing the side view of correctly installed bushings, but it still drives me crazy trying to understand the mechanics of all this. I talked with a supplier of poly bushings today and he told me he was not aware of any modifications that needed to be made to his bushings. His bushings come as a single unit, outer sleeve, bushing, inner sleeve all together, but some bushings seem to come in 3 pieces. Has anyone else experienced any of this? Makes me wonder how many Corvettes are running around with incorrectly installed poly control arm bushings. Sorry for such a long post, but this stuff is interesting to me and this is what this hobby is all about. Thanks in advance for any comments.

[Terry M.]

Re: Polyurethane Control Arm Bushings

Maybe it is me, but I wouldn't use poly bushings. I have heard cars with them squeak, and it would drive me loonier than I am.
BTW: I know a bunch of Chevelle guys who put those bushings on their cars -- and they all squeak. I don't believe they all installed them wrong.

[Joe L.]

Re: Polyurethane Control Arm Bushings

Sorry if this discussion has taken place previously. If so I did not find it. I am in the process of replacing the control arm bushings on my 69 Vette. I am leaning on using polyurethane bushings. However just about every article I read on this installation says it is more difficult to install than stock rubber bushings. Not that they are harder to press in, but they just take a little more time to install properly. As I understand the articles it may be necessary to modify the inner sleeves by shortening them to eliminate any unwanted movement forward and backward of the A-arms. Also I understand that the rubber bushings do not move, the rubber just flexes as the A-arms go up and down. The poly bushings actually turn on the inner sleeve. The inner sleeve does not turn on the shaft because it is a tight fit and is held in place by the large washer and bolt. If properly installed the the large washer will not press against the bushing but only the inner sleeve. The spacing is critical between the large washer and the bushing itself. If properly installed they will not squeek. I have seen drawings showing the side view of correctly installed bushings, but it still drives me crazy trying to understand the mechanics of all this. I talked with a supplier of poly bushings today and he told me he was not aware of any modifications that needed to be made to his bushings. His bushings come as a single unit, outer sleeve, bushing, inner sleeve all together, but some bushings seem to come in 3 pieces. Has anyone else experienced any of this? Makes me wonder how many Corvettes are running around with incorrectly installed poly control arm bushings. Sorry for such a long post, but this stuff is interesting to me and this is what this hobby is all about. Thanks in advance for any comments.

Thomas-------


I wouldn't touch the polyurethane bushings "with a ten foot pole". I would not consider, even for a moment, the use of these bushings.

As far as I know, there is not a single automotive manufacturer that uses these bushings in OEM installations.

[Peter J.]

Re: Polyurethane Control Arm Bushings

Thomas,
I am about to get my 66 back on the road after a several year break and in the back of my mind is the God awful squeaking my car made over every speed bump I passed over. I used polyurethane bushings anywhere I could and have regretted that decision from the first time I drove the car.
I greased mine just like the instructions said and my advice is the same as Joe's and Terry's don't do it. Unless you have a track car you don't need them. If you can hear bushings squeak over the sound of side-pipes it is incredibly annoying.

[Dan M.]

Re: Polyurethane Control Arm Bushings

I put good quality A-arm bushings in my 68. They squeaked from day one. Big mistake in my opinion and they are no longer installed. My two cents.

[Michael M.]

Re: Polyurethane Control Arm Bushings

Thomas I hate to go against the grain on the previous posts. I have polyurethane bushings in all my cars for the last twenty years without a squeak. I feel they are far superior then rubber. It's called technology for your suspension. I love the road race feel for the street.

[Jeffrey S.]

Re: Polyurethane Control Arm Bushings

Many years ago I replaced the worn bushings on the upper control arms on my '69 with polyurethane bushings. The instructions specified that you had to trim the steel inner sleeve to certain dimensions. Fast forward to several seasons later and, after induring the constant squeaking, one of the bushings worked its way out and the a-frame came crashing into the fan shroud putting a hole in it and putting the car on a flat bed home. Not knowing any better at the time I called the vendor who told me to re-measure the sleeve and and put it back together. "You shouldn't have a problem". Until the return trip from Bloomington. This time, when I felt something strange in the steering, I checked the bolts on the end of the crossshaft and found one to have worked its way out to the point of almost falling off again. Another flatbed trip home. The moral of the story--- DON'T USE POLYURETHANE!!!
Jeff

[Michael W.]

Re: Polyurethane Control Arm Bushings

Add my name to the list of those that made the mistake of using poly bushings. I fell for the marketing hype of supposed 'improvements' and of course using the placebo effect was convinced that I had indeed seen an improvement. I do not believe it is possible to push a car hard enough while driving legally on the street to see a true improvement in handling. The harshness is apparent while driving on rough roads, some upgrade.

Although going off on a tangent, using poly at the front trailing arm location may do more harm than good as this material introduces a factor of rigidity where the opposite is required. C2/C3 trailing arms rotate slightly along their axis (longitudinally) as they move through normal up/down travel due to the basic four link suspension type and the half shaft being used as the upper member. Standard rubber bushings allows the required two dimension flex, poly does not. Nonetheless, this is probably one of the most common 'upgrades' the non-cognoscenti jump at.

I have heard directly from one vendor who took exception to my comments on another forum that softer poly bushings are being manufactured, but have no personal experience. In my mind they still remain as the ultimate fix for a non-existent problem. This is every marketeers dream product.

[Duke W.]

Re: Polyurethane Control Arm Bushings

I am in the process of replacing the control arm bushings on my 69 Vette. I am leaning on using polyurethane bushings.

All I can say is: Why?

Duke

[Ronald L.]

Re: Polyurethane Control Arm Bushings

Every engineer thinks they are smarter than the guy that engineered the original part, just one minor thing, they don't have that durability test track to verify what really will happen as Jeff and others have pointed out.

Nothing like that good ole' original part...

[Thomas F.]

Re: Polyurethane Control Arm Bushings

Michael, did you install or have the bushings installed and do you remember if you had to make any modifications to the inner sleeves when your bushings were installed?

[Michael W.]

Re: Polyurethane Control Arm Bushings

No mods required, they essentially installed the same as OEM bushings. I did not understand the dynamics of the stock rubber bushings at the the time and just what a good design it is.

[Duke W.]

Re: Polyurethane Control Arm Bushings

Every engineer thinks they are smarter than the guy that engineered the original part, just one minor thing, they don't have that durability test track to verify what really will happen as Jeff and others have pointed out.

Nothing like that good ole' original part...

The fact of the matter is that none of the REAL engineers on this board have ever advocated major changes to vintage Corvettes - just minor changes that basically amount to "tuning" and optimizing the OE performance.

It's the back yard hotrodders that think they're smarter than the engineers who designed and tested these cars.

Duke

[Joe L.]

Re: Polyurethane Control Arm Bushings

The fact of the matter is that none of the REAL engineers on this board have ever advocated major changes to vintage Corvettes - just minor changes that basically amount to "tuning" and optimizing the OE performance.

It's the back yard hotrodders that think they're smarter than the engineers who designed and tested these cars.

Duke

Duke------


For the most part I agree with you. However, there are cases in which non-original components provide advantages. For example, stainless steel exhaust systems eliminate the need for system replacements and eliminate RUST.

71+ fan clutches provide superior cooling if one goes through all the effort to change the waterpump, fan and pullies to the 71+ configuration.

The one piece oil pan gasket is another example. GM eventually went to a one piece pan gasket for PRODUCTION engines. But, it took them a lot longer than it should have. None of the oil pan gaskets available from GM will work with older engines, so the aftermarket is the only way to get later technology into an earlier engine.

There are many other examples, too. In many cases, the improvements "borrow" on the pieces developed for later Corvettes. GM would likely have used them on the older cars if they had been invented at that time.

So, one can make many judicious upgrades by taking a clue from later models. However, in general, one needs to be VERY cautious about "changing things". Sometimes, the aftermarket has a "better idea as a result of the years of technological advances that have been made since the 60's. Not too often, though. Certainly, these polyurethane bushings are not one of the "better ideas" the aftermarket has come up with.

[Duke W.]

Re: Polyurethane Control Arm Bushings

I absolutely agree, and that's what I meant by tuning/optimizing. There are many cases where later design parts are superior and and even a few where earlier parts might be a better choice, but they are usually GM design parts.

My choice over the OE plain steel pipes would be aluminized rather than stainless.

There are very few cases where aftermarket design parts are a better choice, but one that comes to mind is the small journal SB connecting rod.

Duke