@Mikey914

I bought a set of the rubber rear trailing arm bushings in the 914Rubber GB when they first came out (can't remember when that was). I am just now getting around to installing them and ran into a problem. I did a test fit to see how hard they would be to install and was shocked to find I could easily slide them into the trailing arms by hand AND could slide the pivot shaft in by hand. In fact, I'm not seeing much difference from the polygraphite bushings they are meant to replace. If anything, these fit even looser. I'm wondering I was sent the wrong ones. My understanding is the rubber bushings should be a tight fit and require a press or similar to install as seen in Ian's video. Is there a good way to know what I have? These are stamped "WDG" on the flange side which is different from the stamping on the first set of bushings I bought.

Sounds like the rubber shrank. Yous should not be able to do either with the bushings.

They are not so easy to actually install. The OD of the bushing compresses it onto the shaft.

Give that a shot. I'm sure you will see why we designed them the way we did.

Yeah, what I'm saying is that I can easily slide the bushings into the trailing arm and THEN slide the shafts in by hand with surprisingly little effort so something seems amiss. I'll play with them a little more tomorrow.

As far as I have learned, suspension rubber bushings are designed to be press fit on the shaft and the tube. Movement is only within the rubber itself. (Thats why you must lower the car on ist wheels before tightening the lock nuts.) Any movement between the bushing and the corresponding parts will eventually lead to (rapid) detoriation. Never use grease or oil for assembly. Turpentine works.

Yeah, that doesn't sound right Brent. I installed a set of 914Rubber TA bushings / new shafts about 6 months ago, and I had to use a press. I have not installed them on a car yet.

I will say it was significantly easier than the previous pair of bushings I had done. Those also required a press...and about 8 hands.

Rut Roh!

Could it be that you're using the 914Rubber bushings with the OEM pivot shafts rather than the heavy 914Rubber SS pivots? Maybe the SS pivot shafts are larger OD than OEM?

Exactly my next question. I just rechecked all the bushings and there is something seriously wrong here. I checked all of the bushings and all are a snug, hand-press fit into the trailing arm bores. Then the shafts either slide right in with no effort (as in, they will drop in with gravity alone) or require only moderate hand pressure to press them in without lubrication. In the worst case, there is even noticeable play after the shaft is installed.

The only things I can think are that either the rubber shrank, or the bushings were designed for the SS pivots and those have a larger OD than stock. I just swapped my SS pivots with another member for a set of pristine OE shafts because I couldn't justify the extra weight for a street ride so I can't check.

@bbrock

The problem is that the trailing arm holes can get expanded from normal use. I have installed several sets and had several sets of trailing arms in a side by side test. The bushing in one arm can be loose in another. I never liked the poly bushings and now use the rubber bushings which are more difficult to install but account for the variation on trailing arms.

They're not the torsion bar bushings are they?

Bruce, I believe he is using the rubber bushings not poly.

with great interest since I have this job ahead with 914 rubber bushings, refreshed trailing arms and replated stock shaft, not SS new 914 rubber.

Yep, installing rubber bushings. And yeah, the are definitely trailing arm bushings and not for the front torsion bars.

I do not find rubber bushing listed on the 914 Rubber site. I bought these and they are definitely poly, not rubber. They give no description of the material. Is that what you bought?
The problem is that the arms get over sized holes from the leverage exerted on the bushings from cornering.
You can JB weld them into the arms.
The 914 SS shafts measure 1.105" as do the original shafts at the larger diameter. The original shafts have a .010" step. I do not know why it is there as it make the installation more difficult with rubber bushings.

Very interesting, I have never been able to slide a shaft in without quite a bit of pressure being required. I would suspect there may be some variation on the trailing arm side.
Mark

Yes, the ones on the 914Rubber screen shot are rubber per the two pictures below
Although the part number doesn't seem to match...

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Yes those are mine I recognize the taper at the bottom. Can you take a pic of exactly what's happening? I'm most curious as to the ID on the trailing arm. We have sold used and installed these and have never been able to easily install them without some pressure.
-Mark

Okay, I have some pics and numbers. But first, my bushings are packaged exactly like what @Montreal914 shows. That part # matches the poly graphite Daystar bushings 914R also sells but those Daystar bushings are what I pulled out to install these rubber bushings and they are not the same (as Mark already confirmeed).

For grins, I decided to try a full install without press or clamps. I couldn't find my bottle of liquid soap and didn't want to risk getting caught using the wife's froofy stuff so did this WITHOUT LUBE of any kind. The bushings press into the trailing arms with moderately firm pressure with the heel of the hand. I think that is normal. The pivot shaft fits more snugly in the inner side but still didn't fight me as much as I would expect based on reading other's experiences. I was able to drive the shaft into the inner side fairly easily with a rubber deadblow. Again - no lube. There is enough squish on that side that I cannot twist the shaft by hand but judging by the ease it drove in, I couldn't be sure it wouldn't spin under driving conditions.

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Now here is the shocking part. Once the shaft was installed, I was able to press the outer bushing in with the shaft in place by hand - no lube. With the outer bushing installed, I could easily spin the bushing by hand. And of course, I can also pull the bushing out by hand.

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Now for the ID of the trailing arm, my caliper only reaches about 3/4" into the bore so I can't measure the ID through the whole depth that the bushings reach but I measured across four direction on each bore and here are the numbers:

Inner
1.494"
1.493"
1.479"
1.496"

Outer
1.509"
1.490"
1.514"
1.4985"

So the outer does average a tad larger than the inner which kind of makes sense because I expect that side gets more force to stretch the metal.

I haven't measured or tried to do a full install on the other trailing arm, but based on my tests fitting the bushings one side at a time, I expect it to be the same. The shaft is has a more snug fit in the inner side but not an extraordinary amount of difficulty to try to get it to slide in. The shaft on the outer side is quite loose.

I believe we have a very similar setup. My trailing arms were rebuilt by Bruce Stone after powder painting. The bushings are from 914Rubber (I think from the group buy) and the shafts are re-plated by Bruce.

Here is some data showing the ranges measured at various angles around (~4-5) using a Mitutoyo 12" digital caliper:

Stock shaft as mentioned by Bruce earlier have a small step down close to each end.

Shaft 1, first end step: 1.0980 to 1.1000
Shaft 1, first end: 1.1015 to 1.1020 (27.978 to 27.991mm)
Shaft 1, second end step: 1.0990 to 1.1000
Shaft 1, second end: 1.1020 to 1.1035 (27.991 to 28.029mm)

Shaft 2, first end step: 1.0965 to 1.0985
Shaft 2, first end: 1.1020 to 1.1050 (27.991 to 28.067mm)
Shaft 2, second end step: 1.0995 to 1.0990
Shaft 2, second end: 1.1030 to 1.1050 (28.016 to 28.067mm)

Trailing arms dimensions vary more on the inside bushing since the weld is right there and has deformed the tube. Again ranges from a few measurement around.

Right side inner: 1.4930 to 1.5070
Right Side outer: 1.5060 to 1.5090

Left side inner: 1.4850 to 1.5100
Left Side outer: 1.5005 to 1.5025

I haven't tried to fit the bushings yet...

Well at least they were easy to install by hand with out special tools, clamps, presses, lubes ! Hope it all works properly for you !

They shouldn't be loose...

that is not a good thing!

I believe the small step in diameter on the original shafts is a result of cutting away and therefore smoothing the welds on an automatic lathe during production. The original rubber bushings are tight enough to compensate for those tolerances.

@arno914
I agree. Another argument as to why poly bushings are a poor material choice for trailing arm bushings. They will not contact the full surface of the original pivot shafts.

Well, since it was clear the 914R bushings are not going to work for me, I decided to bite the bullet and buy a set of Elephant Racing bushings. You can buy just the bushings without tools or pivot shafts for $200 and they sell the two installation tools for $40 each. $280 for four little chunks of rubber still seems pretty steep, but that's $90 off the full kit price.

The ER bushings are significantly different from the 914R. Here is a Daystar poly/graphite on the left, 914Rubber OE replacement bushing in the middle, and ER on the right.

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As expected, the poly/graphite is quite a bit harder than the others. I don't have a way to measure durometer but the old pinch test says it takes about the same force to compress the cylinders of the 914R and ER bushings. The 914R material might be a little harder than ER but the wall of the 914R bushing is thinner and that might make it appear harder. If there is a difference, it isn't easy to detect by pinching. Here is a side by side of 914R (left) and ER (right) where you can see a difference in wall thickness.

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Another major difference is that the ER bushing is quite a bit shorter than the other two and has a recessed groove just below the outer flange.

Here are some measurements of the three bushings in millimeters.

Numbers are arranged Height, Wall Thickness, ID, OD

Daystar 54.45, 5.0, 28.14, 37.94

914Rubber 54.02, 5.13, 28.79, 38.33

Elephant Racing 45.81, 6.73, 26.38, 40.04

Of course, the real test is how do the ER bushings fit. I installed a pair using a large pipe clamp and the instructions included. The bushings required liquid soap lube to push into the trailing arms. I did it by hand but it took considerable effort. That was a good sign. Cranking the shaft in with the pipe clamp wasn't the worst thing I've done, but it sure wore out my arm by the time it was done. It took some serious pressure to work it in and I sure wouldn't try doing both arms without a good break in between. The end result is that the shafts are in and they are TIGHT

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My honest opinion is that the 914R bushings need more development to fit the variances in trailing arm IDs out there.

Thank you for sharing

There is quite a difference in diameters (ID and OD) between the 3 candidates and a substantial increase in the interference fit for the Elephant Racing bushing!

It will be interesting to compare the dimensions with @bdstone914 bushing's coming from Restoration Design EU.

Can you share a picture of the tooling?

Of course! Here are the two tools. Nicely made but honestly, I think they would work just as well if they were hard plastic like the 914Rubber A-arm bushing tools to reduce cost.

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Here are a couple shots using a poly/graphite bushing to show how they work. The small tool gets pressed into one of the bushings and the pivot shaft is pressed in through the opposite bushing. When the shaft meets the bushing with the tool in it, the conical bevel centers the threaded portion of the shaft to align it to follow the tool through the bushing. The large tool acts as a stop to prevent pushing the bushing out of the trailing arm and is hollow to receive the small tool as it is pushed back out of the bushing by the pivot shaft. Works pretty slick.

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Here's a pic of them in action.

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Very clear!

I've decided to go with 85 duro RD bushings vis Bruce . . It will be quite a while before I get around to using them but will be happy to post ID/OD when they become available.

The most important thing to remember about doing this is that the serrated portion on the end there is clear of the outside flange of the shaft which then is bolted to the suspension ear with the special nut. It is most important that the two surfaces are NOT in the same plane. Otherwise the nut can come loose because it will want to compress the flange of the bushing as shown in the first photo.

The other thing about the poly bushings are that because of the material and the fit...they may squeak. To solve this you can drill a zerk fitting in the arm after the bushing is installed to just clear the inner surface. Use an angled zerk...unless you have an angled fitting on the the gun....ask me how I know.

My .02 from experience.