Spring plate "stiction" with new bushings on a '73

[Robert59095]

Hi, All -

I have been removing stiff and hard suspension components on my "new" '73. Out with the stiff rear T-bar, in with the stock one. Out with the rock-hard spring plate bushings, in with new Neatrix stock replacements, et cetera.

When I put the adjustable spring plate into the new Neatrix bushings, I cannot rotate the spring plate with all my strength. Put the outer one on, and things only get "stickier".

Here's my question: Spring/mass/damper systems work best without friction. There is a ton of friction here! Is this normal? Will it break in? Have I done something wrong?

Another related question: The adjustable spring plate is thicker that the stocker, since it has two parts. Should one space the outer bushing holder with some washers to accommodate for this? It seems that without washers/spacers, I am crushing the flange on the outer bushing, leading to more . . . stiction.

Any help you can give me is most appreciated, thanks!

- Rob S.

[Flieger]

Urethane and Polygraphite bushings need to be turned on their outside diameter on a lathe, installed, then turned in the inside diameter on the lathe to ensure circularity and cylindricity. I am not sure about Neatrix.

The rubber ones work in elastic shear. They wind up like a rubber band.

The cars were designed/setup with those bushings so they effectively became a third torsion bar and also contribute to damping with their friction.

This is not so bad. What is worse is poor-fitting plastic bushings which do not function in elastic shear but are simply tight on the shaft. They have significant friction then slip, then have more friction. This gives a wildly varying damping ratio and effects wheel rate, as well. Norbert Singer found this in the early days of RSR development. They picked up a couple seconds a lap with monoballs/needle bearings.

[GaryR]

That's why I love the polybronze/monoball combination. I can move my rear (and front) suspension throughout it's travel with one finger (no torsions installed of course . ) and it's smooth as silk the entire range.

[Robert59095]

Flieger -

I just took out the urethane ones, on the principle that it was transmitting road noise to the tub. You have me rethinking this one.

Gary R -

Free movement is what I want, but I also want isolation from road noise. Will the polybronze/monoball getup do that adequately? Thanks to both of you!

- Rob S.

[pete3799]

With Neatrix bushings you don't want free movement.
As Flieger noted these work in unison with the TB's.
If you want a softer ride neatrix is what you want IMHO.

[Flieger]

If you want isolation, rubber is tops. No maintainance, no squeaks. The elastic is not so bad as long as the rubber is new or in good shape. It has a repeatable "spring rate" that you can tune your suspension around.

If you want performance, go monoballs and polybronze. In the front, you can use Rebel Racing A-arm bearings and avoid the grease work. Suspension1

[porschenut]

The factory bushings, and Neatrix bushings, don't move. They aren't bearings and should have no lubrication whatsoever. The inner and outer circumferential surfaces remain stationary during the entire radial motion of the spring plate, and the rubber deflects to allow the motion. There is an animated depiction of this action on the Elephant Racing website here -> ELEPHANT RACING Tech Topic, Polyurethane Bushings and Friction

[abisel]

Originally Posted by Robert59095

Another related question: The adjustable spring plate is thicker that the stocker, since it has two parts. Should one space the outer bushing holder with some washers to accommodate for this? It seems that without washers/spacers, I am crushing the flange on the outer bushing, leading to more . . . stiction.

When the factory went to the adjustable spring plates, they extended the length of the 4 mounting points by 4mm. So to answer your question, yes, you do need to insert a 4mm spacer.

[Robert59095]

Pete - Thanks for your thoughts.

Flieger - Thanks for that link - great stuff!

Nut - That Elephant Racing link is great - I'm going to go with the Polybronze getup. The nerd in me wants the torsion bar to do the spring work, and the shocks to perform the dampening. What seals the deal for me is that corner balancing with the Neatrix is nigh-on impossible by design, but straightforward when your suspension moves freely.

Abisel - The Elephant Racing Install sheet for the Polybronze gives a wonderful procedure for the spacers. They want 1.5mm +/- .75mm of axial play on the spring plate.

Thanks All, case closed!

- Rob S.
Boulder, CO

[GaryR]

Good choice!