suspension bushings

[jurhip]

It has been some time since I have been on here (or in my car!!!) So I have a few questions.

1. Suspension bushings. Does ANYBODY carry the OEM rubber bushings. If not, what is my best choice. I do not really like the idea of polyurethane bushings due to noise and HF vibration tramsmitted through the body and bolted joints. IMO, I do not think this is good for any body structure.

2. My car came with Koni, and they seem okay (no bounce, etc...) but I need new rear springs. Should I just go ahead and change the shocks while I am in there?

Thanks

[Dave at Pelican Parts]

Most of the rubber suspension bushings are bonded to the metal suspension parts, and are not available separately. Which means: If you want new A-arm bushings, you have to buy new A-arms. If you want new trailing-arm bushings, you have to buy new trailing arms. OUCH!

There are some softer aftermarket bushings for the front ("Neatrix" bushings; they're intended for 911s but they will work for us). The only stuff I know of for the rears are the hard squeaky bushings, the bronze bushings from Elephant Racing, and the roller-bearing setup from Mueller Design Werks (and possibly other places). Each has pluses and minuses...

--DD

[nine_one_4]

When I get to that point, I'm going to try the Elephant Racing bushings. Even Mueller admits they're good and at half the price of the roller bearings.

[jurhip]

I did some research on this bushing matter (very popular topic) and was thinking of isolation possibilities. I do not have the car in front of me, but would it be possible to install bearings or metal bushings at the pivot (like elephant or mueller) and isolate the trailing arm mounting plates from the body via a rubber spacer. This should be technically similar to a motor mount.

Suspension geometry may change slightly, but if you have adjustable spring perches, this could be compensated somewhat. You wouldn't need to drop the arm that much. I think a 1/2" spacer woudl be more than adequate to knock out HF vibration.

Has anybody tried this. Is this even possible or will a lot of welding be required to rework the mounting points?

[Brant]

Originally posted by jurhip
I did some research on this bushing matter (very popular topic) and was thinking of isolation possibilities. I do not have the car in front of me, but would it be possible to install bearings or metal bushings at the pivot (like elephant or mueller) and isolate the trailing arm mounting plates from the body via a rubber spacer. This should be technically similar to a motor mount.

Suspension geometry may change slightly, but if you have adjustable spring perches, this could be compensated somewhat. You wouldn't need to drop the arm that much. I think a 1/2" spacer woudl be more than adequate to knock out HF vibration.

Has anybody tried this. Is this even possible or will a lot of welding be required to rework the mounting points?

I don't think this would work on the rear.
the rear toe is dependent upon the very mounting face that you are proposing to install rubber into.
this would create a situation where toe would be changing constantly as the rubber flexed for every corner.

sounds like a wreck waiting to happen to me.

on the front it might be possible for part of it.

the front stock shock-top bushing is already rubber and already does this. The torsion bar forward mount could probably have rubber added (at the trade off of less precise handling).
The rear of the torsion bar sits inside of the metal cross brace for the suspension. Don't think you could really add rubber there either because it would change ride height as it flexed.

brant

[jurhip]

the rear toe is dependent upon the very mounting face that you are proposing to install rubber into.

Correct me if I am wrong, but wouldn't the original rubber bushings install in the pivot point do the same thing. These maintain rear toe and camber (technically caster too). Being rubber, they will deform and change alignment slightly as they are loaded, hence racers go to bearing type installations.

The isolation required is for HF vibration, hence the rubber spacer used would be fairly hard. Though shear deformation would probably be your worst handling case, this could be compensated slightly by a stiff hard rubber.
Obviously there will be alignment changes thruogh load, but I do not see why it woudl need to be any more that that of the original rubber bushings.

I agree that roller bearings are probably the smoothest acting, but the amount of vibration transmitted through the body is immense. A road going chassis was never meant to cope with fatigue stresses like this. Road going cars see more mileage than race cars, generally, and maintain/inspection is not as intense (at least for me). If I were racing it would be different, but I will give up a slight handling advantage to not degrade my chassis over the long run.

[nine_one_4]

Jurhip, you might find some useful information in this forum .

[Dave at Pelican Parts]

Originally posted by jurhip
Correct me if I am wrong, but wouldn't the original rubber bushings install in the pivot point do the same thing.

They probably do. But they are trapped pretty effectively between the pivot shaft and the swing arm housing, so the amount of deflection is pretty limited--until the bushings wear. The amount of deflection with an isolated mount would depend on the exact design of the setup. Could be a lot more than stock, could be a little less than stock.

Though shear deformation would probably be your worst handling case...

I'd be much more worried about the strength of the isolated mount in tension, myself! From the sound of it, you're talking about having the isolator being the sole connection of the arm to the body, and in a way that puts compression, tension, and shear loading on it! That sounds like a very good reicpie for failure to me...

I agree that roller bearings are probably the smoothest acting, but the amount of vibration transmitted through the body is immense.

Anecdotal evidence suggests that the NVH transmitted to the chassis with the roller-bearing setup is roughly equal to stock, and better than most of the polyurethane bushing setups! I don't know anyone who has hard data on that, though--which is why I specified "anecdotal evidence".

--DD