Rear traling arm bushing selection Options

[technicalninja]

I'm currently restoring the rear suspension on my 75 1.8l and wanted to get other's suggestions regarding rear bushings.

My shafts are fine and I'm planning on re-using them.

I already have a set of bushings.

Mine are the "Daystar" polygraphite set that you can get from multiple vendors.

These are in AutoAtlanta packaging.

These puppies fit stupid loose in the arms...

I worry about squeaking...

I don't like straight poly bushings for the most part.

Would you use them?

What grease would you use on them?
Normal silicon grease for urethane bushings?

914Rubber has a rubber set that are reasonable. $ 44

PMB and Elephant racing have rubber sets that are far more costly. $92, $240

This car will be a mildly upgraded streetcar for enjoyment not competition.

I'm leaning toward the 914Rubber set...

What says the hive mind?

[JamesM]

A couple things to consider with ANY of the single piece plastic/poly bushings out there is that the factory designed the rear suspension to have all movement to be allowed though the deflection of the rubber. All the surfaces that the rubber bushing touches (the shafts, control arm, and mounting ears) are intended to be bound to the rubber bushing, they are not bearing surfaces.
All the single piece poly bushings turn these into friction surfaces and you wind up attempting to slide a bushing on a surface that was not designed to have anything sliding on it, so the performance winds up being very inconsistent, assuming you can even get them installed with proper gaps.

Elephant addresses this by supplying components to act as the friction surfaces, providing their own shafts and thrust washers, but single piece poly you are just grinding plastic on rough metal.


The 2nd issue to consider with solid bushings is alignment. With rubber a good portion of the fore/aft movement of the control arm is allowed via compression of the thrust area of the bushing, with solid bushings this isnt the case and you wind up having to get all the movement from flexing the control arm mounting ear on the chassis.

[Superhawk996]

Ding Ding - Winner (IMG:style_emoticons/default/beerchug.gif)

The 2nd issue to consider with solid bushings is alignment. With rubber a good portion of the fore/aft movement of the control arm is allowed via compression of the thrust area of the bushing, with solid bushings this isnt the case and you wind up having to get all the movement from flexing the control arm mounting ear on the chassis.

Said differently . . . Rigid bushing increase loads on all your suspension bits and chassis mounting points . . . a lot. You wouldn’t believe how much higher the loads are. I’ve seen substantial changes in durability loads just going between different durometer rubber bushings and voided vs solid rubber bushings. Moving to urethane / poly bronze ratchets that up to another level. Move to spherical metal bushings and there would be enormous durability / fatigue issues .

Just because something is good on a track with a very controlled road surface for a race car doesn’t mean it it is “better” for a street car used in the real world.

And we haven’t even talked about the NVH degradation in road noise. Ninja touched on the ride comfort degradation. People’s tolerance for those degradations varies. Choose wisely.