poly bushings in rear lower suspension links
 

First: This is not a conversation about the Watts Linkage and poly vs rubber there. That has been covered very well.

In the process of rebuilding the ole 7, replacing the suspension links seems like a good idea considering the age of the rubber. Oddly enough Energy Suspension sells a DYI kit. Perhaps I can find a universal sized answer. Is there any geometric disadvantages to using poly in this application. dropping near $500 for four links is a tough pill to swallow.

added information
 

from a domestic performance magazine :

Polyurethane integrity and performance are rooted in hardness and how much flex there is in a bushing or mount. Factory bushings are made of rubber, a natural material harvested from certain kinds of tropical trees or from petroleum. Rubber bushings are softer than polyurethane, around a 60-65 Shore A rating. Polyurethane bushing hardness usually ranges from just slightly harder than rubber, around 70-80 Shore A rating, to firm, around 80-90 Shore A rating, to very firm, around 95 Shore A to the harder Shore D rating on the durometer scale.

Then we have this:

https://www.mcmaster.com/#urethane-c...ounds/=1bxunkm

So as I see it, it looks like I can get a polyurethane compound in the same(ish) hardness as OE rubber. To me.. the 60A Poly would be a good bet from my understanding. Hell, it could work for the watts link also.

Following for my own education. I've got all original bushings and are due to be changed.

The lower links need as much flexibility as possible and poly on them are not recommended. Poly on the links can lead to binding as the axle moves causing tail happy dances. Thats my understanding.

I have poly on the rear bar and the watts link which really feels good compared to what it was. Still have the original links

What was surprising to me is that poly has different hardnesses. The off the shelf stuff from Energy Suspension and Prothane is a harder compound than stock OE rubber. If the McMaster DYI poly can be purchased in a hardness the same as rubber without the potential for deforming and rot over time, I would want to go poly. Once again the extra hard poly that is sold in stores as an upgrade is a bad choice for our cars rear end. Oddly enough there is poly being sold that is softer than the OE rubber. They say it's hardness is close to rubber band material.

I see, thats a bit different then. Keep posting as you find out more or do more on this.

The hard part is getting the old rubber out without messing up the structural integrity of the end links. I've seen where folks have burned them out but then I wonder about the state of the steel after that.

I could see using some sort of piano wire and then running it around the edges somehow, but how to do that effectively is not obvious to me. Or maybe use a small drill bit on a dremel and run it around the edges carefully to get the largest chunk out then use a very stiff wire brush on a drill to clean out the rubber thats left. I think I'd rather just by new links if they are still available.

A technique for removing the old rubber is not to burn it out but to melt the outer perimeter of the rubber by applying heat to the metal casing and pushing the rubber out. Follow up is mechanically removing excess rubber. remember you are only need to get the rubber to melt so the bond between the metal and rubber are compromised. You do not melt the entire rubber bushing.

Applying heat to the outside of the link till the rubber starts to bubble and smoke and then using a press or socket is the easiest way, I tried drilling the rubber and cutting it out and then dremalling and that sucked. Once I got a torch it was so easy.

I think the softer urethane will work well. One ghing about natural rubber is it hardens with age, I bet original links have a pretty hard durometer

Done this several ways over the years and have arrived at this procedure:
12 ton or larger press,set links on pressplates,use a socket/drift slightly smaller than the sleeve in center of bushing and press out sleeve.

Select a large deep impact socket,32mm? and press out remainder of bushing. There will be some rubber nibs remaining in end of dogbone,99% of bushing will have been pressed out by this step.
Use Mapp gas torch and char remaining rubber in dogbone,takes about a minute each end.

Chuck link in vise and wire brush (i use a bell shaped brush meant for decarboning valve pockets in cyl.heads)in (air)drill for speed. Put brush in dogbone,turn on drill,centrifugal force from speed pulls the bottom of brush out and into contact with id of dogbone.
Make couple passes(think honing cylinder),rinse with brakleen,blow dry and put in glassbeader.

Wipe down with prep sol,shoot with etching primer,let it flash,then hit with semi flat chassis paint-ready for new bushings.

Whole process takes about an hour for both links,then waiting for paint to dry. This method i feel is quickest,consistent way to do this,the heat used to char the remaining rubber bits is minimal and does no harm to the metal in the links.

I've done this with Watts Linkage also. I've experimented with same and different cars using OE Mazda Links upper and lower and then substituting rebuilt urethane bushed links in mix and match combinations. Majority of time,using urethane in upper and lower links on a mildly lowered car really tightens up rear suspension where it feels good -up to the point of snapping rear end around in a turn. Using urethane bushings in watts linkage and lower links and new OE Mazda upper links instead of urethane imo(flame away) works well(for a street driven car) and is setup i ended up with on my SE. All 1st gens like urethane watts linkage bushings,and some cars are better staying with new OE upper/lower links. I think(imo) spring rates,ride height,swaybar thickness,adjustment, magnify how suspension is bushed good or bad.

I now have 2 reasons to get one of those HF 12 ton presses, this and rear wheel bearings. Problem is where to store it when not using it. My 2 car garage space is precious already.

I am going to state right now that my efforts are going to be reallocated to get the car painted as soon as possible. I may not be able to get to this until early fall.

Have any of you guys ever tried Super Pro bushings? They are based out of Aus, it seems people use their bushing in both the upper and rear trailing arms.

https://superpro.suspension.parts/spf0010k

Not my video but it shows the process.

Can vouch for superpro bushes . They are pretty much the go to here. Much better longevity than other brands. Ive been using them for a decade and no signs of deterioration.
They are stiffer. Ive never had binding issues, although i am running harder springs than stock.
i have played with diff articulation under the car and with the springs out, and they really are getting tortured when you articulate left and right sides. But diff wont be moving like that in normal driving, only in off road situatuons i guess lol.
probably not the ideal set up hence why rubber is recommended, but again i havnt had a problem*, but again im running a stiifer spring set up, especially in front.
The McMaster stuff you mention: is that a pour your own product?
problem i forsee with that assuming the product is able to withstand the abuse of this application, would be to set the bushes accurately. I forsee having to make a really good jig off the standard bars before you remove the oe bushes.
*correction, i have broken a mount off the axle tube once, possibly because of the stiffer bushings. Also had a torquey 350rwhp at the time though.

My 1st gen has had polyurethane bushes in the lower trailing arms for 20 years, same bushes, still in good condition. I think they were superpro. Quite happy with the way it drives, it has super low King Springs in the back.

To get the rubber out I just used a drill, about 5mm, drill a hole straight through the rubber close up to the outer edge, I just pushed it around the circle, I don't remember it being very difficult. I then got a circular wire brush on a drill and just pushed it in the hole and cleaned out the rest of the rubber. No heat or burning stuff was necessary.

The bushes came with a new inner steel crush tube.