I just installed a set of Bilstein HD's on the ol' 94 and while I was in there, I decided to replace all of the front control arm bushings with new poly one's while I was at it.

This turned out to be a non-trivial installation, a few observations from my weekend long struggle:

1. An alignment job will be necessary upon completion. The lower control arm has some adjustability in it's mounting points, but I felt very lucky to have been able to get the horizonal and veritcal mounting bolts in at all, much less into the position that they came out.

2. Stock bushings do not look good after 10 years and 95,000 miles. Mine were torn and decaying.

3. To remove the bushing sleeves from the old bushings for reuse, be prpared to do alot of burning with a torch. We didn't get much of the rubber off of the vertical bushing on the lower control arm and it took alot of time with a wire wheel to get the rest off. (My brother has a friend with an acetylene torch, we burned the bushings out of the control arms, but forgot about the sleeves)

4. There will be alot of pounding, prying and otherwise indelicate use of force required to get things lined up. There were times I was sure that I was ruining threads and bending stuff, but it did finally go back together.

5. The upper control arms are not as difficult to deal with as the lowers.

6. The rear shocks take about 45 minutes, vs. probably 5 hours minimum for front shocks if you leave the bushings alone.

7. Lining up the shock mounting holes on the lower control arm turned out to be very difficult. The angle of the lower control arm unloaded did not match up with the shock mounting holes when it was bolted in at the shock tower. This is one spot that an extra set of hands was essential to pry on things and get it lined up while the other person persuades the bolts into position.

8. Removing the shock from its upper mount required drilling the old shock rod out throught he rusted on nut. There was no way that thing was getting through those threads. I loaded the new ones up with grease prior to reinstallation, but I'm hoping that I never have to take them off again.

I wanted to start this thread for discussion purposes to see if anyone else has had similar experiences, or had any tips to avoid the problems that I ran into for those planning to do this job themselves in the future. One shop wanted to charge me $600 to do this job, now I see why. After I get the alignment done this week, I'll report back and let you know how it feels comparatively.

 

Thanks for the write up, I'll be doing a similar job on my front suspension in the next few weeks..

 

Great write up, (I will not prepare my self for a hefty install charge when I go get this done). BTW what bushing set did you use? and if you don'g mind my asking approx how much and where did you get it.
Thanks

 

I bought the Prothane front control arm set from Thunder Racing. I think they were about $35. I may be switching out sway bars in the near future, so I have left those alone for now. Good luck to all.

 

I drove the car (properly aligned) for the first time yesterday, and the suspension definitely feel alot tighter. Bumps seem to be transmitted through the chassis a little more sharply, but I expected that. Looking forward to putting some more miles on it now without the groaning old deCarbons.

 

Yep, that's called "bind"

 

Steve,

How exactly does the front suspension bind with poly? I'm familiar with the mechanics surrounding the rear control arms binding, but the front still seems to have the full range of motion to me. My rear bushings are still stock.

 

Seriously, Does having poly on the front cause anything to bind up? Thanks.

 

I would like to know also. As I'm about to embark on the same adventure.

 

I found this thread earlier today. it seems like some think it binds and some don't. Steve must be in the poly = bind camp.

http://web.camaross.com/forums/showt...ntrol+arm+bind

 

yep, that's why.

There were several much longer posts about this a few years back that included several engineers, racers, and a few anecdotes of stiction leading to losing it on a corner.

Here are your options:

Rubber - designed so that the outer surface binds to the arm, and the inner surface binds to the inner sleeve... then deflection is what travel is about.

Poly - same design as rubber, except that the deflection is much less, meaning the arm either a) doesn't rotate, or b) the inner sleeve slides on the surface of the poly. As you can imagine, a happens first, then b kicks in randomly (once the friction between inner sleeve and poly is exceded by the twisting torque). People refer to this nasty habbit of poly as "stiction", and on a high speed corner pushing the limit of your tires, this reajustment of a sticky poly bushing can lead to REALLY bad consequences.

Delrin - this is a very hard plastic material that is used to replace the "deformation bushing" design with something much closer to a bearning. Delrin requires the same type of machining as most metals, and the surface if VERY slick if polished right. The outter surface of these usually bind to the arm, while the inner surface slides on the surface. Think of this like a poly bushing, but will NO deflection and VERY low friction... no stickion.

Del-A-Lum - this takes the Delrin bearing a step farther by using a thick billet aluminum sleeve to make up the outside of the bearing, and a delrin core to make up the inside. The rotation surface is increased significantly over the Delrin bearing. The aluminum sleeve binds to the arm on the outside, and is closely machined/polished on the inside to mate to the outside of the Delrin bearing. The inside of the delrin sleeve is the same as a delrin bearing. These are reportedly stiffer than delrin bearings alone, and the friction/resistance to rotation is even less. Think of the Del-A-Lum bearing as a 3-piece rod end instead of the delrin as a high-quality 2-piece. Either is good in moderate situations, but you're probably better off with the extra protection/durability if pushing the limits.

Obviously this, and the delrin bearing are limited in use, since they are designed to prevent ANY off-axis rotation... very bad idea for rear LCA's, but GREAT for retaining wheel alignment under load in an Upper Control Arm

Spherical bearings / Heilm joints / rod ends - These come in 2 different designs as discussed above (2 piece or 3 piece), and even in 2-piece come in a full range of quality/load capabilties. Spherical bearings typically are used by full-out race suspensions as there is a lot of vibration transfere to the chasis for obvious reasons.

These also have the adjantage of having no restriction to a 3rd axis rotation (within reason, most can only rotate a 120* arc. I use QA1 2-piece ends in an aluminum PHR a local guy built for me... 30,000 miles later it's still rock solid. For those looking for more, try Aurora 3-piece ends.


It depends on the application obviously. I do use poly sway bar mounts and sway bar end links... but the travel on these are obviously limited, there is no rotation to speak of, and resistance to motion is the whole point.

 

I havn't messed with my front suspension much, but here's the plan for this summer:

- LS1 brakes w/C5 calipers, SS lines, Hawk HPS+ pads, cryo'd rotors (have it, just need time to install it all)
- 1LE lower control arm. (Gotta give Dal a call)
- Global West Del-A-Lum upper control arm (pending cash )

- Koni SA shocks (free 1" drop)
- ditch the rear spring isolator and cover the springs with a rubber hose (free 3/4" drop )

- hollow 35mm front Sway Bar w/poly bushing/end-links (Sam Strato will be getting a call once I get some free cash to throw on the car )

Most likely the sway bar will be the only install by itself... everything else will probably be easier to do in one weekend.

 

Thanks for the write-up Steve. To be honest, I haven't pushed the suspension very hard since the re-bush, and I'm not sure that I could tell if it was binding or not if I did. Like I said before, it doesn't seem like the front suspension is limited in it's range of motion over less than perfect pavement, but who knows.

I like your proposed set up as well, and would have likely gone with a similar set up myself, if funds were permitting.

The firmness that I reported earlier though is, I think, more due to having brand new Bilstein HD's in place of 100K mile deCarbons.

 

Binding? Can you elaborate on where and how they bind? All I see is a description of materials.

Lonnie (ESP Z) has energy suspension bushings up front and says that they don't bind.

 

I think I elaborated fairly well. If you want to run poly in a rotational application go right ahead, it's not my car.

I have energy suspension bushings in static mount positions (sway bar bushings and end-links), rod ends for the PHR ( I went cheap with the QA1 2-piece, but they're working great anyway), and plans for ... well, I've already gone into it above.

graphite-inpregnated, and throughly greased poly bushings are essientally a cheap attempt at rod ends or metal/delrin bearings. The bushing is no longer ment to deform during rotation (like rubber does), but to remain rigid and slide on top of the bolt. The greese isn't there to absorb noise... it just lowers the friction you need to overcome before the inner surface starts to slip on the poly (the "stiction if you will).

Some designs take this effort a step further and intentionally machine the poly's inner surface to be grooved. The grooving is designed to hold more greese, and to reduce the contact area the bushing had with the inner sleeve/bolt. In an application that is continually rotating back and forth you can imagine that keeping the bushing clean, and the greese in the bushing is a limiting factor.

The greese-less design of rod-ends and delrin doesn't have this limitation/maintainence. And you have much lower risk of binding the suspension due to a dry bushing, water contamination, built-up dirt/brake dust, etc....

As I said, most poly set ups will be fine daily driving, and even more so when freshly installed or greesed. But I'd make sure I pick the application, try to keep them clean, and check them before any serious racing situations (which is a good idea with anything on the car I suppose ).

Some love them, and some don't. I don't... in rotational applications.