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Rear Suspension Bushings

Now that the 4 vs 6 .....er ...debate has been settled to the satisfaction of all let's move on to the "great Bushing debate" that raged on the shop floor at the gittogether.
Amid the back ground roar, you may have missed it.

What is the ideal set-up when using the aftermarket bushings?

Should the bushing & shaft stay still and the swing arm tube rotate around the OD of the bushing?

or

Should the bushing and swing arm act as one and rotate around the OD of the shaft? This is the condition I have....at least on one side.

Since I had one side doing each (or thought I did....my demonstration didn't work out too shiney) I was gonna take it apart nohow.

NOW we gots pics. The thingys have been in there for 3-4 years.
First, inner console ........

Note the wear marks on the ear and the impression from the shaft.

and the outer support ....

So, is this good? Feel free to jump in.

Since I'm not an expurt on suspensions (like I am on engines) I could use opinions.
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Old 12-30-2002, 03:57 PM
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I don't know, but my uneducated guess would be the bushing staying with the arm and the shaft moving in the ID of the bushing. Maybe you should take a poll.
Old 12-30-2002, 04:11 PM
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I agree with the previous post since the stock front bushings are glued to the a-arms and the torsion bars move inside the bushings. Actually I don't think it matters one damned bit! I'd recommend looking at the inner console very carefully for cracks and get those repaired, if any while everything is apart. Good luck.
Old 12-30-2002, 04:15 PM
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I'm doing this right now. Obviously, the original rubber was bonded and thus did not move on either the shaft or the arm, plus the shaft is held from turning by the knurled ends. Notice that all the manuals tell you to align the outer piece parallel to the arm when installing since they assume your bushings are still rubber. This is for eliminating preload.

For the replacement plastic bushings, if you don't modify them for grease fittings or something, it doesn't matter, they could turn on the shaft or the arm could spin around them and it wouldn't change much. I put mine in with the grease only on the inside bushing surface, so I assume they will not spin in the arm (much).
Mark S.
'70 914-6
Old 12-30-2002, 05:56 PM
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JP, you know my stance is with the above posts. And if you remember, I stated that if someone were to use the grease zerk and have the busning move in the arm, or both, the zerk would have to be installed in a surface mounted bung welded to the outside. I know you pointed out the problem wiht the thrust issue. You have a good point there. So, chicken or egg?
Old 12-30-2002, 06:19 PM
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I've heard that instead of welding the zerk fitting onto some type of adapter so that it doesn't interfere with the bushing, you machine the bushing with a little groove in it so that if the bushing does spin, there is no interference. Kinda difficult to explain I know, but think about crankshaft bearings and you'll get the idea.

The problem you're experiencing with your trailing arms wallowing out yer inner attachment points is probably due to the nut used for the inner attachment point of the trailing arm. This nut is a lock-nut, although some don't realize it. Once you have this area welded up or refinished or whatever, buy yourself some new nuts when you re-assemble. I think you torque them to 100 ft./lbs. if I remember correctly.

If you look at the nuts (and if they're factory), you'll notice a little slice of material taken out of them. That's the locking type nut. I'd explain how it works, but most either already know, or don't care. As an example, think about when you use two nuts crammed against each other on a bolt when you're trying to get them to not back off of whatever you're using the bolt for.
Old 12-30-2002, 07:08 PM
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JP, if you do it right the bushing will spin on the inside diameter as well as the outer diameter, and it will spin at exactly half the speed of the shaft
Old 12-30-2002, 09:01 PM
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My main concern is the wear on the ear that has been done by the rotation of the bushing flange. I use lock nuts and torque the crap outta them. I also check them after every AX. No oblongation
of the holes.

I also inspect the ears for cracks at the same time. The ears have been seal welded as have all the areas on the console left un welded by the factory .....the bad factory welds have been ground out and re welded.

I guess the wear on the ears isn't too bad considering the use the car has had and the time involved.....but them ears.... those whole consoles make me paranoid. I have seen/heard about too many failures there to rest easy.
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Old 12-30-2002, 11:28 PM
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F'in board, I had a nice long detailed post ready to submit, but it ate it up. JP, have you thought of making a bushing that fits up against the ear of the rear suspention? Maybe out of hard plastic or derlin-poly-ounm-graph-spacestation-stuff? You could(if you have a lathe) turn it so it fit right up against the ear nice and snug, compensate for the toe or camber that it would affect, and change it out every few ax's. Just a wine and beer induced thought...might not even work.
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Old 12-31-2002, 12:16 AM
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Quote:
Originally posted by Rob-O
The problem you're experiencing with your trailing arms wallowing out yer inner attachment points is probably due to the nut used for the inner attachment point of the trailing arm. This nut is a lock-nut, although some don't realize it. Once you have this area welded up or refinished or whatever, buy yourself some new nuts when you re-assemble. I think you torque them to 100 ft./lbs. if I remember correctly.
Rob-O,
Please explain this statement, I have no idea how the nut is elongating the hole.
Mark S.
'70 914-6
Old 12-31-2002, 10:18 AM
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I believe he is talking about the hole in the ear for the shaft.
If the nut holding it backs off, the shaft gets to banging around and elongates the hole in short order. This must be repaired by welding. Left to it's own devices, it will rip out and ruin your day.

I can't get a torque wrench in there at either end....even with a crows foot. I use a 22mm (AIR) box end and a BFH to tighten them. They come off the same way. I had one come loose once. It makes some noise (clunk, clunk)......that's when I went to the BFH.
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Old 12-31-2002, 11:37 AM
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Quote:
Originally posted by J P Stein
I believe

.. snip...

BFH to tighten them.
Is a BFH a special Porsche tool? Do you have a part #?

Can't wait to see ulf out there running.

Any plans to add a wheelie bar for those top fuel starts?
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Old 12-31-2002, 12:29 PM
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The largest BFH I have personally swung was the 320 oz model... I wuz a lot younger then. I do have one each 160 oz, 80 oz, 24 oz, 16 oz, & a baby 12 oz. You haven't really lived till you hunker down under a ship and go after something with a sidearm swing using that 320 oz unit.
Wheeuu.....I got short of breath just thinkin about it.
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Old 12-31-2002, 01:15 PM
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You need a BFH on those? Damn, JP--you just need to eat some more o' that BBQ and yer wife's very good cooking!! Work on the "lbs" part of "ft-lbs". I was able to torque the trailing arm nuts by putting a nice long (18") box-end wrench on them, and doing a one-handed pull-up on the end of the wrench.

OK, not really a pull-up, as I was laying on my back and only pulled the top half of my body up about 8", but I still put a lotta weight on that...

--DD
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Old 12-31-2002, 08:21 PM
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Yeah, but I don't have as much "road hugging weight" as you.
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Old 12-31-2002, 09:25 PM
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JP,
Smart Racing has a "tip" on installing the rear bushings.
"Installation tips: For the rears, we recommend you press the outer bushing into the cap and then hone or lathe-cut the ID to the OD of the spring plate's outer snout. The rear inners should be fitted to the torsion tube and then the ID of the bushing sanded or honed to fit the OD of the inner snout. The fronts, push the bushings into the stamped steel housings and then sand, lathe-cut or hone the ID to the individual end's size. I know all of this is a pain in the ass, but it is the only way to really get it right. Too much bushing "sticktion" can effect proper suspension movement and handling - this sticktion also makes corner weighting the cars nearly impossible. Use any good quality moly lube prior to final installation. "

Geoff
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Old 01-01-2003, 06:52 AM
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Thanks, JP. Yes, that is exactly what I meant.
Old 01-01-2003, 08:16 AM
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JP, why not use these bronze bushings at:
http://www.elephantracing.com/suspension/bushings/bushings.htm
Even come with a grease fitting!

Geoff
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Old 01-01-2003, 09:00 AM
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So far, it appears that Elephant Racing only has A-arm bushings. Nothing for the rear 914 trailing arm, where JP is having his problem.
Old 01-01-2003, 09:19 AM
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JP--- What ever happened to the discussions we had with Brad and the needle bearing bushing? I know they were expensive ($800 a set) but it really sounded like the answer to the torque/rotational motion the rear arm goes through in tight cornering. As I understood, Brad was going to check and see if he could get them made cheap--er, I mean more inexpensive.

milt mcpherson
Old 01-01-2003, 06:54 PM
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