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A-arm rubber bushing installation advice needed.

I am just about to put the Smart Racing rubber A-arm bushings onto the A-arm.

Here is my plan. I'd love your advice!

1) Wet-sand imperfections from A-arm surfaces. Lube with silicone grease. Put A-arm in freezer (or outside in the cold).
2) Bushings in simmering heated water to make pliable.
3) Push heated bushing into outer bushing holder.
4) Push outer bushing holder, with bushing, onto A-arm with a mighty force.

I figure that the shoulder on the bushing proper, driven by the outer cover's edge, should allow me to force the bushing around the A-arm round surface.

Your comments appreciated!
John

EDIT: Here are some useful links:
Thom's pic page:
http://vintagebus.com/howto/susp/

Chuck's original bushing install/zerk fit thread (with cigar and mustache...):
Suspension bushing, the right way

What the t-bar in your car probably looks like right now:
Warning! Before upgrading torsion bars, change bushings (pics)
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'78 Targa | Horizontally Opposed

Last edited by Jdub; 12-03-2003 at 08:07 AM..
Old 12-01-2003, 07:01 AM
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not to be a smart ace, as i can be, why would you cool the A arm? seems to me that would make it contract and harder to set bushing. it would cool your bushing fast too.

just wondering
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Old 12-01-2003, 07:18 AM
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The thought is that the A-arm might contract and make the task a bit easier. Following this logic it would make sense to heat the outer bushing holder as well...

Jw
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Old 12-01-2003, 07:22 AM
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There is no way you can do this installation without going through the methods indicated on removal of excess material. You need to first get outer circumference to fit the housing with minimal binding. After this is achieved you then need to enlarge the inner dimensions so the bushing slides on the a arm with no binding. It takes patience and some method of reducing the polyurethane, either by lathe or by sanding with power tools. Care must be given to go slowly and to repeadedly cool the bushing by soaking is some cold water prior to fitting. (They get hot when sanding and it changes the fitment dramatically.) I've done it to 2 sets of cars and have the method down, but it is a pain at first. I guess this is why the bronze bushings have become popular. If you somehow get them on with your method, you will have binding and a very noisy, creaky car. Lastly, add some zirc fittings for future greasing. If you search the archives, there are some prior threads on the subject.
Old 12-01-2003, 08:36 AM
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The bushings I'll be putting in are rubber, like the OEM in shape and elasticity. My impression is that they will distort to fit.

My take on using rubber is that I don't want to deal with the poly squeaking, and Chuck's bushings, though nicely designed, are just a bit too pricey for me, plus I think my street-based Targa will not benefit from the rigidity the pure brass bushing causes.

That's the thought process to date. BTW I found that my setup had the classic rubbing T-bar and deformed bushings.

John
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Last edited by Jdub; 12-01-2003 at 08:43 AM..
Old 12-01-2003, 08:40 AM
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John,

I discussed this product with smart racing, and they said they didn't recommend it as a DIY because it is very difficult to install. They recommended shipping the arms to them for the installation, if I recall they wanted about $400 for the service.

I don't know if that recommendation has changed. Perhaps you should ask them to suggest a proper technique.
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Old 12-01-2003, 08:59 AM
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I thought the only way to get a rubber bushing like the factory ones was to buy new a arms and needed hardware. The only ones I've seen from SmartRacing were the poly ones that everyone else sells. Do they have something new out?
Old 12-01-2003, 09:35 AM
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Quote:
Originally posted by 89911
There is no way you can do this installation without going through the methods indicated on removal of excess material. . . .
I don't think you want to do that.
My understanding is that the bushing material should be well compressed (as installed). .. . .else they may feel sloppy.

I think that Jdub is on the right path.
btw; Heat soaking them will make them much more pliable too.

So what does John Walker recommend, for installation tricks?
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Old 12-01-2003, 09:47 AM
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I was a bit leary about poly bushings since I tire quickly of a harsh ride. So I got the rubber install done by SmartRacing a couple winters ago. Not cheap though. Cost me just under $400 like Chuck said.

They did a very nice job. Before I sent them out, I indexed the bushing retainers by filing a tiny notch on the retainer and the A-arm itself. Both arms came back exactly as I had sent them. Index marks lined up perfectly.

I believe the bushings were bonded to the arms as well since this is how the rubber bushings are supposed to work. The bushings deflect/twist. The arms don't rotate independent of the bushing like with the aftermarket replacements. It appeared to me that some type of goop was applied inside the bushings at the ID to hold them onto the A-arm. If I recall correctly, SmartRacing sends the arms out to someone else for this work. I called to check on the progress and I was told the arms were due back to them any day so............
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Old 12-01-2003, 09:58 AM
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I think John Walker thinks this is a waste of my time! And I must say, but for the compression of the rear bush that causes the T-bar to scrape in the A-arm, the bushings were probably good for another 25 years!

When I pointed to an A-arm at John's shop he just laughed and told me it was such a PITA to get them on/off the question really is why bother replacing, esp. with the identical bushing type. That's a good question and I will be your guinea pig tonight, on a very special Front Suspension Rebuild Hour.

Tell me about heat-soaking? Is that bathing in a propane flame bath, lightly? Or are we talking oven time?

My kid got such a kick out heating up the old bushing outer covers. We stunk up the outside drive and he was dancing around like a primitive. Ya gotta love it!

John
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Old 12-01-2003, 10:02 AM
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I agree. The rubber a arm bushings flow and tire easily leading to the torsion bars hitting the steering rack. This is magnified with heavy torsion bars, track tires and hard driving. One other point is to enlarge the holes in the aluminum steering rack that the torsion bars go through. The larger torsion bars have little clearance and may still hit. I've had zero problems with the rebuilt a arms with the harder poly bushings. Don't forget the zircs.
Old 12-01-2003, 10:10 AM
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As Kevin says, rubber bushings are not intended to have a "friction surface". They accommodate movement of the control arm through deformation, not slippage.

Therefore I would not use silicon grease to assemble. I would try to find a suitable adhesive that will act as a lubricant during assembly, then set up solid.

Since they don't slip/rotate once installed, it will be important to properly index the mounts to the arms to achieve the correct static position. If you marked the mounts before disassembly, you should be all set. Else you might be looking for a spare arm that is removed from a car.
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Old 12-01-2003, 10:21 AM
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Chuck:

The old dodge back in the bicycle shop was hair spray. It is slick as all get out when you start, but sets up pretty solid. It took LPS or equiv. to break it free, plus judicious use of an air nozzle.

I just don't see how the rubber bushing is intended to perform the function that the t-bar is performing? The rotation of the A-arm is a pure t-bar event, right? That is, the deformation of a glued-in bushing is never going to augment or replace the action of the t-bar in rotation. What am I missing here?

EDIT: Or is it the wear from friction I should be concerned about? The rotation causing incremental wear over time. Now that would be a problem.

John, thinking out loud...
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Old 12-01-2003, 10:26 AM
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John, I sent you a PM.
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Old 12-01-2003, 11:21 AM
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John, Paul has recently done this. I did it a few months ago. The bushings I used were not the hard plastic type, but rather they were very firm rubbery ones. Firmer than stock.

The stock bushings are glued to the a-arm, and also glued to the bushings home 'cups.' They do not slide. They deflect.

Replacement bushings, unless you use a very soft rubber and glue them in, are going to slide, rather than deflect. Upon installation, I noticed that the inner hole fits the a-arm perfectly, but that when the bushing is captured into its holder-cups, the inner bore is crimped, causing binding against the a-arm. The trick is to remove a little material at a time FROM THE OUTER SURFACE so that when bolted or pressed into their holders, the inner bore will not crimp against the a-arm.

I also installed the Zerk fittings, and am glad I did. One bushing started to squeak, so I spooged grease into it using the Zerk fitting, and all is now quiet.

I explained this to Paul as he was planning his install. I'm interested to know from him whether his experience was like mine.

EDIT: If I had glued these hard rubber bushings (again, not the plastic ones but rather the firm rubber ones) onto the a-arm, I'm pretty sure they'd be destroyed by now.
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Old 12-01-2003, 11:41 AM
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Super, John is not using the same bushings you have. His are indeed rubber, similar to the factory parts and intended to deform. FYI, on your bushings you really need to remove the material from the inner surface using a lather. Otherwise the id will never be truly round.

John, I didn't really understand your question. The factory bushings don't really wear, per se. They "cold flow" from the weight of the car which allows the arm to get off center. This is why rubber bushing replacement is not a mileage related thing, it's an age thing.

I wouldn't use hairspray. I'd use a water proof adhesive.
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Old 12-01-2003, 12:28 PM
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Chuck:

I am wondering why Porsche glued the rubber bushings in. Did they do it to 1) reduce squeak (will they squeak?), 2) prevent abrasive wear between surfaces by, instead, permitting deflection, or 3) desire the A-arm to return to a zero point after deflection, as the t-bar does, since this is what happens when deflection occurs.

That's the crux of it. Really, what I am wondering about is if these bushings will squeak. I don't think so....?

John
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Old 12-01-2003, 12:39 PM
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I think they glued them for all the reasons you list.

On your last point, returning to a zero point, this is actually an important feature. Stock rubber bushings actually move with very little friction, this is because they deform instead of slipping. They do add "spring rate" which attempts to return them to the natural position regardless of which direction they are approaching it.

Contrast this with an ill fitting or poorly lubricated polyurethane bushing. They don't deform, they slide. These can introduce substantial friction, resisting all movement of the control arm regardless of it's position.

Lift the bumper of a polyurethane equipped car, release and measure the height. Now push the bumper down, release and measure the height. The height difference is due to friction as the polyurethane bushings battle the tbars effort to find the natural position (and winning), I've seen a difference of more than 1 inch! Factory rubber bushings won't do this, since they are attempting to center without friction.

That is why you want any replacement bushing to be as close to friction-free as possible.
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Old 12-01-2003, 01:04 PM
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Jeepers Wally, these rubber bushings are as tough to get on the A-arms as getting Eddie a date.

I can now see why Smart charges what they do to put the bushings in - they will require either 1) a press and/or 2) mucho removal of material to fit.

I don't have a press, and it makes no sense to remove any material (ID or OD) from a soft rubber bushing that really needs as much material as possible. Comparing side to side, it is easy to see how the original bushings flowed out to fill the area as they are longer in length.

So, it is off to the archives to again study the work the rest of you have done. I am hesitant to use the poly bushings as I don't have a lathe to do this properly. That would leave Chuck's bushings, Smart Racing, or another fix I have yet to find.

If you have any comments I am all ears. Many thanks for the comments to date,
John
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Old 12-02-2003, 05:09 AM
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You are making the process of fitting the polyurethane bushings out to be harder then it is. I can see using a lathe on the od but as far as using it to enlarge the id, I think this is actually making is more complicated. The biggest aid I found was getting a large wood dowel that almost fits the id. Then I built up the thickness with tape and finally very coarse sandpaper was carfully taped with the overlapping edge left on the trailing edge of the sand paper. I used a drill press but you can do this with a power tool by hand. The its just a series of sanding the id while always turning to give uniformity, cooling, and test fitment. The od is just done by building this dowel up so the bushing fits very tightly and then sanding by holding the paper against the turning bushing. Cool, and test fit.

The od should be done first so it fits without any binding. It also can be glued in place since no movement is needed at the outer portion. The bushing with the front and rear housings in place should then be test fitted on the clean and polished a arm ends. The should slide on smoothly with slight resistance. These again, should be cooled completely. The actual sanding process actually removes the hard polyurethane by getting relatively hot, allowing the material to then be removed by the coarse sandpaper. When the completed a arms are finished, they should slowly and smoothly drop from horizontal to vertical.

Make sure to keep the respective bushing with its fitted a arm end. This might sound complicated, but the first time I did this for my car, it took possible 2 hours. The next time for my brothers, it took 45 minutes. This same technique works for fitment of polyurethane springplate bushings. This is nothing to take away from Chuck's bushings. These weren't around when I tackled this a few years ago. The do seem like a nice alternative, especially when it come to greasing them.
Old 12-02-2003, 05:37 AM
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