Hello all,

I tore apart my rear suspension to do a general checkup of my trailing arm bushings and suspension mounting ears. I was getting a clunk from the rear end which I believe now was worn CV joints, but I figured it is better to be safe so I pulled everything apart "while I'm in there". I would like to show some pictures and get comments about whether everything looks ok, particularly the trailing arm bushings.

First, here is the driver's side inner ear.

Passenger side ear.

Next, a trailing arm bushing (they all look about the same).

I measured the shaft and it is centered in the bushing, but the bushing is not centered in the housing (at least the edges are not). It's about 1/16" to one side as shown.

Like I said they all look the same...

Here's an inner ear, both look identical.

No ovalling that I can see....

Are there any other checks I can do on the suspension bushings? They look sound to me...

The suspension ears look ok to me too, the driver's side is especially clean. The pass side has a little bit of wear evident but nothing major in my opinion, looking for second opinions though...

What should I do to them before I put everything back together? Hit them with some POR-15?

Ummmm 30 years old.....what will hurt to replace them?

A lot, since there aren't any suitable replacements.

Let me elaborate - Weltmeister, people report fast wear and squeeks

Elephant - seems better, but expensive. Maybe not suitable for street car?

Roller bearings - too expensive, maybe not suitable for street car.

If it ain't broke...

Them damned plastic bushings.
There was no other replacement for the rubber
till fairly recently, so I used em'. Here's a pic of mine after 2 years use.....note the deformation. They don't pivot on the shaft or tube but rotate with the swing arm tube, thus the wear on the ears. The IDs of my bushings were about .04 out of round. The material seems to deform while just sitting under the weight of the car.

Ouch, J P.

That is why I don't want to replace mine unless absolutely necessary.

Problem is, I can't tell very much from looking at the outside... They could be totally split and half disintegrated halfway down and I would never be able to tell...

Tangerine Racing (Chris Foley) does custom fit/installed delrins. He states they are as effective as the roller bearings. Price is less the the elephant parts.

Usually, the exposure to the elements will cause the outer flange(?) to come apart first. If the outsides look good, leave em' alone.....Meuller bushings are cool tho

JP, urethane or delrin bushing?

I'd go with Delrin for commercially available pop in place. It's some tough stuff and forms a great lube with steel.

My other choice would be UHMW Polyethelene. Unique stuff, Ultra High Molecular Weight material must be pressure formed, and you can't wear it out. Great natural lubricity and it is almost impossible to wear. Used it for skids on some military projects. Loaded a 200 lb guy in the box and we drug him around the parking lot. Tipped it over and couldn't find any wear.

I've seen 1/2 inch steel plate worn through in 6 months and replaced with this stuff. It never wears out. Good impact resistance too. Comes in rods and sheets.

Some info.

) What is UHMW-PE?

UHMW Polyethylene is a Linear Polymer with a molecular weight in the range of 3,100,000 to 6,000,000. Therefore, UHMW-PE has a molecular weight average 10 times that of conventional high density polyethylene resin.

2) What are the benefits of UHMW-PE?

The high molecular weight is what gives UHMW-PE a unique combination of high impact strength, low co-efficient of friction and abrasion resistance that outwears carbon steel 10 to 1 making it more suitable for many applications where lower molecular weight grades fail.
(More Info. See UHMW - Properties or UHMW - Specifications)

3) Where is UHMW used?

UHMW is a self-lubricating material which exhibits excellent wear and abrasion properties in addition to extremely high impact strength. Markets which would utilize these attributes would be snowboard bottoms, material handling, packaging, food processing and automotive just to name a few.
(More Info. See Applications Library)

Ken

Oh yeah,

Polyethelene is what they use for milk jugs. Rub some steel on that for a feeling of how good a bearing it is.


Milk jugs are soft. UHMW polyethelene is much harder (like delrin) and made by a pressure/heat forming process.

Ken

Those were the Welt poly graphite.
My experience is with rubber, the Welts, and Meuller's Needle Brgs.

I installed derlin bushings on one front A arm. It bound up so tight that it took 30-40 lbs of force to move the arm...striction.
Meuller got hold of me & said "Wait, I got something for ya"
So I never got to "test" those.

When someone says something "is as good as" it kinda tells you what the gold standard is, eh.

Ken,

You might want to look at the cold creep properties of UHMWPE; they may not be quite as good as PU or Delrin. This would cause rapid deformation from constant loading (like when your car is parked for a while.

The Weltmeister bushings that I have, are a simple casting. They are not cylindrical (round), and you can see evidence of bubbles from poor casting technique. I put them on a mandrel, chucked them up in my lathe, and trued them up. I did buy some PU extrusion from McMaster-Carr, and may choose to machine my own. The design of the Welt bushings falls short of containing it's shape. It would benefit greatly if it were contained on all sides in a rigid metal structure like the garden variety Energy Suspension Systems control arm bushings are.

Also, I did quite a bit of research, and found that the whole squeaking issue is likely due to over-compressing the bushings either radially or axially (or both). Line-to-line or very little compression is all that is required, and the harder the bushing, the less compression should be applied. The standard issue silicone grease, as it turns out, is not the best but rather boat trailer wheel bearing grease (waterproof) or a teflon based anti-sieze.

Andys

The problem with the delrin bushings sticking can be attributed to one thing. When they are installed in the trailing arm, they compress. That makes the hole in the middle smaller, thus binding them to the arm.

The trick is to use a hone to open the bushing until the shaft will slide in. Then yhou have no stickage.

I use the race version of the bushings. They are harder.

The best choice if the bushings look ok is to just leave the OEM ones in, right?

I think I am going to strip those ears and hit them with some POR-15 to protect them.

I think there are several things at play with trailing arm bushing design.

One, the bore for the bushing is frequently not round and can distort the bushing bore (causing bind).

Two, both bushing bores are not lined up perfectly in the arms. This means the shaft can bind from the misalignment in bores. Add distorted bores to it (from 1) and you have some fun.

Three, found a machinist's reference on the web bitching about some materials having bores distorting over time ( one month for Delrin) They suggested annealing the parts. I've never had a problem myself. Nylon (the wonder moisture sucker and sweller) is a different story.

Looking at these issues, the factory design isn't bad as it is quite forgiving with metal bore inserts in a squishy rubber ring. Metal inserts hold the bore ID (one), and the rubber "gives" to compensate for (two) misalignment.

It is my understanding that Racer Chris align bores the delrin bushings AFTER installation in the arm. Problems 1-3 solved!

Ken

Jeff,

The misaligned (pounded out) one in the pic bothers me. Gonna have to play alignment games to adjust it out (if you can).

Ken

Well, after having built my own custom trailing arms replicating the original design, has brought to light the alignment issue. If you were to look very closely at the pictures I posted in my "Custom Trailing Arms" posts, you may notice that the pivot shaft tube (that contains the bushings) is very slightly deformed. This is due to my having to heat the tube in strategic areas to shrink it into alignment after welding everything together; i.e. insure the two bushing bores are on the same axis. From this experience, I may make slight design changes to eliminate the need to do this on future assemblies. I had no out-of-round issues, as the bushing bores are part of a separate component in my design.

Distortion over time is exactly why containment is necessary. Any plastic will creep over time when under load; some sooner than others.

Andys

Ken, which pic looks bad to you?