rear poly bushings on outboard end of CA

[blueovalz]

Throughout the years of reading comments about the aftermarket poly bushing for the outer ends of the rear control arms, I've not heard any mention of the size difference between the OEM steel inner sleeve verses the aftermarket size.

 

Specifically this. The spindle pin OD is nearly identical to the OEM bushing steel sleeve ID. In other words, the OEM bushing slides onto the pin with little to no play (or in other words, the pin would slide snuggly into the control arm's bushings). On the other hand, the aftermarket (at least the ones I have) poly bushing kits use a steel sleeve that has an ID that is .011" larger than the spindle pin's OD. My concern is that IF I ever install these poly bushings (the outer ones), will this "play" or extra clearance cause problems later in the life of the suspension. I realize that when the bushings are installed, that once the spindle pin's end nuts are tightened, that these sleeves are pulled against the strut boss with quite a bit of force, and thus may not move. But intuitively, this play does allow the control arm to move in respect to the spindle pin should these nuts ever loosen (something that would not happen with the tighter OEM steel sleeves), and something I would want to avoid.

 

So the question I ask is: Has anybody attempted to separate the OEM inner steel sleeve and use it with the poly bushings instead of the steel sleeve supplied with these bushings? I have looked into this, and found the OEM sleeve's OD is about .032" larger than the aftermarket sleeve, which means it is a little too tight to slide into the poly bushing, so...

 

I guess I'm having a real problem with "building in" some slop into the rear suspension on something that should be designed better.

 

Bushing data:

OEM - Sleeve .629" ID and .785" OD, 1.820" long

Control Arm bushing receivers are 1.179" ID

 

Aftermarket - Sleeve .640" ID and .753" OD, 1.833" long

Bushing is 1.187 OD.

[mom'sZ]

Terry:

 

What brand of aftermarket bushings are we talking about? I used the energy suspension ones and had to take a brake cylinder hone to them and slightly hone them until I could slid my spindle pins into them. My front ones were a tad loose though, and I did exactly what you said, I used the original inner sleeve, but it slid right into the new poly bushing.

[JMortensen]

Your statement about the nuts on the end is the real answer here. The nut and washer captures the sleeve so that it can't move, and then the inner poly surface pivots around the sleeve. So the sleeve shouldn't really ever move. But I know you like to be creative, so read on...

 

I was looking at getting some Kevlar bushings from John Coffey, but it looks like he doesn't have them anymore, and then katman goes and details his rear control arm bushings in this thread: http://forums.hybridz.org/showthread.php?p=592258#post592258. Certainly you could make some bronze sleeves that were closer to the correct size and take care of this issue that way.

 

My main concern is bind and stiction in the suspension. I still don't know how I'm going to resolve my concerns... but I have an idea. Since our last collaboration on the toe adjuster was so productive, I'd love to bounce this idea off of you:

 

Monoballs in the control arms at both the inside end and the outside end.

 

Outer end--I downloaded the Aurora Bearing catalog from their website, and the 5/8" Com-10 monoball has an OD that is .008" larger (1.1875") than your measurement of the receiving end of the control arm. So lets say you use those sleeves that came with your poly bushings. Section them so that they can be used as spacers to work on the ball in the monoballs. You'd still need the OD of the monoball fitted into the end of the control arm. I'm not sure that the .008" interference wouldn't be too much. I really don't know, but once the correct amount of interference is found the end of the control arm could be honed if needed and the monoball could be located in the end of the control arm either by inside snap rings, or by bushings, which in this case instead of providing the pivot could be just installed as spacers that sat against the race of the monoball.

 

Inner end--I figure the inside end would be less critical since even the front hole is pretty large. I seem to remember a thread where you had said that a 3/4" rod end fit right over the end of the inside of the control arm. That would mean that the inside end could be done the same way as the outside, using a bushing to capture a 3/4" monoball housing. I have the OD of the 3/4" rod end as 1.4375".

 

The main problem I see here is how these locating bushings would stay in place. They would probably need to be bolted together somehow or set in place with a set screw. They couldn't be captured the way the bushings are normally, because when you tighten down the big 24mm bolt it would freeze that pivot from moving entirely. So the sleeves have to be captured by the nuts and bolts, and the monoballs need to be captured some other way. I suppose the other way to do it is to make an OD spacer from aluminum then capture it with an inside snap ring at the ends of the control arms. Not sure how much metal you need to have to machine a groove in the control arm and still have some strength there though.

 

Maybe inside snap rings on the bushings for the outside end, and set screws on the inside end since the inside pivots come apart I'm thinking snap rings would be hard to do.

 

I've seen race parts manufacturers use monoballs this way in place of bushings in Porsches, but all I ever saw was the catalog, so I don't know how exactly it was done. The ones I saw in person all had the end of the control arm hacked off and a rod end installed on the end of a custom control arm.

[blueovalz]

Hmm, more things to think about. Good points Jon. I have looked into the monoball on the inside for some time. and my draft solution was to have a machined block made in which the monoball would slide into a large round slot holding the outer race, and then bolting this "saddle" up into the OEM bushing retainer. Perhaps some degree of modification to the OEM bushing retainer (the upper part that is part that is part of the body) to perfectly match (and overlap at the edges for shear force restraint) this machined monoball retainer.

 

Obviously my bushings are not Energy Suspension!

 

More thinking...head hurting

[mom'sZ]

The nut and washer captures the sleeve so that it can't move, and then the inner poly surface pivots around the sleeve.

Thank you Jon, after I installed mine I had asked about how that worked and had never really gotten an answer. I would like to reduce stiction as much as possible also. That's why I asked katman about the sphericals. To me that poly bushing pivoting around the outside of that sleeve doesn't sound to stiction free. (glad I lubed it) Anyhow, your knowledge of all things automotive is impressive.

[mom'sZ]

Obviously my bushings are not Energy Suspension!

opps... sorry

[JMortensen]

Thank you Jon, after I installed mine I had asked about how that worked and had never really gotten an answer. I would like to reduce stiction as much as possible also. That's why I asked katman about the sphericals. To me that poly bushing pivoting around the outside of that sleeve doesn't sound to stiction free. (glad I lubed it) Anyhow, your knowledge of all things automotive is impressive.

No problem, thanks for the compliment. I'd say most of my Z knowledge came from here, so you're in the right place...

 

Terry has a habit of turning an idea into reality in a very short timeframe. Hopefully we can get him into this idea and solve both of our issues.

 

Terry, thought of another way to locate the outer aluminum bushings. Get correct OD pipe. Cut .25" off end. Cut that in half. Now you have two 1/2 moon shaped pieces that are .25" wide. Weld these to the upper half of the bushing supports. Capture bottom of the bushings with the clamshells / front diff crossmember. Done...

[JMortensen]

More: http://www.pelicanparts.com/techarticles/911_monoball/911_monoball2.htm

[blueovalz]

Yes, this was the direction I was heading on that.

[JMortensen]

One issue I've come up with is that our poor man's toe adjuster might not be the best idea with a full monoball rear control arm. Let's take an extreme example: If we had 1/2" toe in per side, the inner control arm bushings would normally flex ~1/4" per end to give us the angle needed (not really because the rear is larger and would flex more, but you get the idea). If we have aluminum cases or sleeves that locate the monoballs, the SLEEVES won't pivot or give to allow the toe change. The monoball is more than capable of handling this misalignment, but the aluminum bits are not. I think that you'd bind up the toe adjuster WELL before you hit the target. This is an extreme example, but the point is just to show that the aluminum parts can't pivot.

 

Normally this is not a problem because toe changes on other control arms, Arizona Z Car's for example use a threaded adjuster to make the control arm longer. When the adjuster makes the end of the control arm longer, it still stays perpendicular with the monoball on the other end of the spindle. So the monoballs pivot and their housings stay perpendicular. Our toe setup doesn't make the control arm longer, it changes the angle that the control arm sits at. I don't think that a radical toe setting will bind the monoballs, but they will stress the ends of the control arm, which could potentially be a lot worse...

 

I think that moderate toe changes or 0 toe settings will still be possible if this new setup comes to fruition, but I might have to back off on my rear toe setting a bit and maybe go from 3/16" total to 1/8" total. John said that his Kevlar bushings were as hard as aluminum and he still managed to run 1/8" toe in. I would ASSume that there is probably enough distance between the front and rear bushing so that the misalignment of the sleeve in the bushing cups is minimal enough to allow the same here.

 

The other solution might be to start with a G machine bushing and machine it to accept the monoballs. Then adjust that instead of using the poor man's toe adjuster. Personally I hate adjusting the stupid G Machine bushings, which is why I got into the toe adjuster in the first place.

 

It's been a slow Monday and I've been a little fixated on this... can you tell???

[blueovalz]

I considered this same issue of the "misalignment" of the bearing verses the casing for the monoball, but concluded that any misalignment could be easily handled by the bearing (much like the sperical bearing on a tie rod which must rotate within a wide range of angles or the TC rod monoball shown earlier). In fact, I would not even consider a monoball if I knew the shaft would ALWAYS be aligned with the axis of the bearing, but instead use a sealed roller bearing (or something similar) instead (they are much smaller and durable, but cannot take any misalignment). This is where the monoball becomes necessary.

[JMortensen]

You know maybe I thought about that one a little too hard. Now that I have some time NOT thinking about it, it seems like the spacer bits would still be perpendicular to the centerline of the car. Because our toe adjuster doesn't swing out in an arc, it moves the bushings straight out. So nevermind, that shouldn't be a problem.

[JMortensen]

http://www.metalsdepot.com/products/alum2.phtml?page=rndtube&LimAcc=$LimAcc

Part #T3R2375 would make a good starting point I think. 2" OD, 1.25" ID aluminum tube. The price on that website looks high @ $27.12 per foot and no price break until 6' of material though.

 

I pulled my G machine bushings out of the garage. The ends are 2" OD on the tips of the hex part, would need to be turned down to 1.580 in the middle to fit the bushing cups. Then turned on the inside to accept the 1.4375" OD of a 3/4" bearing, and need a snap ring groove in there as well. That's pretty much it. The ID of the tube is 1.25" so it would have enough wall thickness to take all of this machining pretty well I think.

 

On the outboard end I was thinking why not just get some 1 3/16" OD tubing, which is our 1.1875" that we need. Cut two spacers, one for either side of the monoball. Hone the end of the control arm to press fit the monoball. Press the monoball and a spacer on either side. Tack weld the spacers at the end of the control arm.

 

Cut the sleeves to the correct length. That's pretty much it. The trick seems to be finding a machinist who would want to do the lathe work on the inners for cheap.

[blueovalz]

1.58000" - 1.4375" = .1425" wall thickness is really thin if I'm going to cut a groove for a clip. An alternative is two short cylinders clamping the outer race into position. these cylinders, one on each side of the race, would be held in place by the nut on the outside (in front of the front monoball), and on between the inner race and the framing on the arm? Shearing would need to be addressed. Anyway, it's off to work, so I'll look at this later.

[blueovalz]

Jon (and others),

 

Here is a drawing of what I've come up with as far as using the #12 spherical bearing you mentioned. I would have it machined as a single piece on the lathe with the 3/4" (#12) spherical bearing pressed into it, and held in place with a circlip. Shims or spacers on either side would be carefully fitted to compensate for OEM tolerance differences to ensure no pre-loading of the bearing took place when it is finally assembled.

 

 

This would then be used with the stud inserted into the OEM CA tube as pictured below (the rod end would be replaced by the sperical bearing).

 

[JMortensen]

That's a brilliant idea Terry! Simple yet brilliant. So much better than the snap ring...

[blueovalz]

And the outboard bearing would be done a little different being the bearing OD is so close to the bushing retainer ID.

 

[JMortensen]

I had just figured on welding the sleeves in on the outboard end. I suppose a compromise would be a set screw on one side so that the bearing could be pressed out and replaced, and weld the other side. It'd have to be a short set screw though.

[blueovalz]

That's a good point Jon. A concern I have, thinking about it now, is that I might need to turn the outer ends of the spindle pin down from .629" to .625" in order to use the 5/8" bearings. The metric sizes were unusable due to a very large OD of the race. This fact would require that I remove the bearing prior to removal of the spindle pin. Welding the inner sleeve in place instead of the outer sleeve could be one way to get around this. But another thought is why not use plain old roller bearings. For me anyway, this is an option because any toe adjustment will be performed away for these bearings. Thus these bearings will always be aligned with the axis of the tubes welded to the end of the CA. Then I could safely use the spindle pin to push/pull the bearings out of the tube, and used sealed bearings as well.

[JMortensen]

The bearing might not be adjusting the toe, but it still takes loads from just about every direction. Makes me wonder if a roller bearing would be sufficient. Think of the load that bearing is going to get when you're hard on the brakes. Monoballs are good in any direction, making them the safer choice in my mind.