Question on designing "hybrid" delrin suspension bushings
 

I am planning on making a set of delrin bushings for my '98 NB.

However, I am concerned about the binding issue brought forward by those in the know, concerning the adjustment points in the control arms.

One solution I can think of is designing a hybrid bushing with a steel sleeve, delrin center section and a rubber outer layer. The rubber would be 2 to 3 mm thick, to allow for enough lateral movement to facilitate toe adjustment. This is for the rear suspension.

The rubber section will be bonded to the delrin, of course.

What do you guys think?

I have another hybrid thought for a related problem.
Dual steel sleeves (the outer one being a mm shorter), and needle bearings between them and a "standard" PU bushing surrounding it all.
The goal is to reduce the torsional binding (poorly maintained PU can stick a bit).
Bronze might be a better choice (sales pitch).

But this is just a thought and will never happen, I promise.

Regarding rear toe, if there is advantage of have a bushing of one hardness or two different (part delrin and part rubber) I don't know. The smaller rubber part would have to take all the angle deflection since the Delrin would not flex at all (if there is something softer that can flex).
But I'm just bored at work, so there must be better post coming, soon.

I searched for binding delring control arm bushings and only found one comment below and in the same thread others not having issues. I've installed and run delrin control arm bushings in four Miata race cars at this point and all of them had full range of motion without binding when complete. I could bring the assembly to full compression (no shock/spring etc.) and when I let go it would fall to full droop. What am I missing?

I think its more a concern of being able to adjust toe/caster. IMO it shouldnt be a big deal there, on the formula car we run the same style cam bolt adjusters and our delrin bushings have like a 1/8th wall thickness and we can get adjustments there without binding. We didn't design the car to have those adjustments at the inner control arm pickups because we were afraid of the same binding issue.

The rampage miata guys have the same concern and have delrin everywhere except in those spots tintuba mentioned where they have poly. They claim that IL motorsports told them to do it that way.

We used to make solid delrin bushings all the time for the racecar guys and for industrial applications when I worked at the machine shop. Pay attention to your tolerances so you don't bind, and make sure to set them up for grease channels from the zerk fittings and win at bushings.

This is good to know..
Did you have rear toe set when you were doing the full droop test?

Yes and no. All the bolts were torqued down at the marked settings from the OE bushings for the droop/compression test. Then the it was realigned after suspension was fully assembled. I can see how some opposing camber bolts could cause bind for radical toe, or to compensate for mechanical differences. I guess I was fortunate to have all things (fairly) even and straight, and in the interest of neutral toe.