Quick Long Arm Question

Sorry about starting another long arm thread. I searched and couldn’t come up with an answer. I’m in the process of building my lower arms and there is some confusion on where I put my poly mount. For one end I have a PolyPerformance bushing (PP-BA200) and the other I have a large RE Superflex joint (RE3792). I have seen it both ways and I would like to know what the positives and negatives are for each. Any help would be appreciated.

Thanks
Jaromy

I believe the axle end of the arm will see/require more movement then the axle end. I would put the RE joint at the frame end.

JnJ said:

I believe the axle end of the arm will see/require more movement then the axle end. I would put the RE joint at the frame end.

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That is what I was thinking but I have a friend that just did a LA kit on his ZJ and he made them the oposite of that.

I think that RE sells their arms with the RE joint on the axle, and the bushing on the frame. At least that is how I had them when I used their control arms. Juice

juicexj24 said:

I think that RE sells their arms with the RE joint on the axle, and the bushing on the frame. At least that is how I had them when I used their control arms. Juice

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Unless someone changes my mind that's what I will be doing.

If you put a poly bushing on the frame it will have to take all of the flex on articulation, which poly generally does not like to do, and which will transfer a lot of force to the frame. Or, you can put the johnny joint on the frame for unrestricted motion and the axle bushings do not have to do any rotational work, which will extend the life of those bushings.

If you design a four-link radius setup, the axle end bushings must be able to flex fore and aft (one arm moves forward on compession and the other drops back under droop). A 36" arm needs about 1/4" of fore/aft bushing motion in each direction (the entire system needs about 1/2"). A johnny joint cannot provide this motion, and you will have bind on both ends of your setup.

This is why a setup like Clayton's uses johnny joints on the frame end and rubber on the axle end. The rubber provides fore/aft movement and the frame end joints provide all of the rotational motion. Don't look to a standard four link Jeep setup in order to understand the motion of a radius arm setup as they aren't comparable. And I am not sure I'd want poly anywhere in that setup as it will probably cause binding no matter where you put it. I would either keep rubber on the axle end or do a three link with johnny joints all the way around.

Nay

The only way I can explain it is, get a broom and hold it out infront of you in both hands. Now imagine it as the axle, your arms the links, and your body the XJ. Now move the axle (Broom) in motions that a typical axle would follow while wheeling.
In my mind's eye, it seems you require more movement from your shoulders (frame end mounts) then your wrist (axle end mounts). This may be bs, but I don't believe so.
BTW, I have JJs at both ends.

ditto Rubber at the axle and RE joints at the frame end.

JnJ said:

The only way I can explain it is, get a broom and hold it out infront of you in both hands. Now imagine it as the axle, your arms the links, and your body the XJ. Now move the axle (Broom) in motions that a typical axle would follow while wheeling.
In my mind's eye, it seems you require more movement from your shoulders (frame end mounts) then your wrist (axle end mounts). This may be bs, but I don't believe so.
BTW, I have JJs at both ends.

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Exactly. Your wrists require almost no twisting motion, which is what a johnny joint provides, but they would have to press into your forearms or pull away, and johnny joints do not allow this motion.

You don't have a radius arm setup with johnny joints at all six mount points, do you??? Just a single upper arm I hope???

Nay

Nay said:

If you design a four-link radius setup, the axle end bushings must be able to flex fore and aft (one arm moves forward on compession and the other drops back under droop). A 36" arm needs about 1/4" of fore/aft bushing motion in each direction (the entire system needs about 1/2"). A johnny joint cannot provide this motion, and you will have bind on both ends of your setup.

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Would this be the same principle if I were going to use only one upper? Your examples are great but what I don't understand is why a company like RE would be the opposite. TIA

Jaromy

RE is not opposite.

On an RE TJ LA kit, the spherical bearing is at the frame end.

On there standard 4 links, it's at the axle, but that is not what is being discussed here, is it? I'm asuming we are talking radius arm style?????

CRASH

Nay said:

Exactly. Your wrists require almost no twisting motion, which is what a johnny joint provides, but they would have to press into your forearms or pull away, and johnny joints do not allow this motion.

You don't have a radius arm setup with johnny joints at all six mount points, do you??? Just a single upper arm I hope???

Nay

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Dave, I have one LCA with JJs at both ends, then a radius arm or Y style arm, lower with JJs each end and upper with Heims both ends. So yes, mine is actually a two link (all radius arm setups are).

JSmall said:

Would this be the same principle if I were going to use only one upper? Your examples are great but what I don't understand is why a company like RE would be the opposite. TIA

Jaromy

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With one upper arm you do not want the deflection of a bushing at all. Use all JJs or RE Joints.

CRASH said:

RE is not opposite.

On an RE TJ LA kit, the spherical bearing is at the frame end.

On there standard 4 links, it's at the axle, but that is not what is being discussed here, is it? I'm asuming we are talking radius arm style?????

CRASH

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I am thinking about using one upper

JnJ said:

With one upper arm you do not want the deflection of a bushing at all. Use all JJs or RE Joints.

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Excuse my ignorance but does in make a huge difference? My buddy has this same setup on his ZJ that he beats the snot out of and it has held up fine. Plus I already have all the parts.

JSmall said:

I am thinking about using one upper



Excuse my ignorance but does in make a huge difference? My buddy has this same setup on his ZJ that he beats the snot out of and it has held up fine. Plus I already have all the parts.

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With only one upper arm you have removed the bind you would get with two uppers. You use the rubber with two uppers because of this bind (from axle rotation). With one arm you need the axle fixed rigidly. I believe you will go through a lot of bushings if you wheel it.

JnJ said:

With only one upper arm you have removed the bind you would get with two uppers. You use the rubber with two uppers because of this bind (from axle rotation). With one arm you need the axle fixed rigidly. I believe you will go through a lot of bushings if you wheel it.

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Sounds good. I would only need to order two more RE joints. If I decided to go the other route and use my parts I have...would I use the poly bushings on the frame end?

Thanks

If you do two uppers, the poly should go on the axle end as explained in several of the other post. If you do one upper and use the poly, I'd still put it in the axle end.

JnJ said:

If you do two uppers, the poly should go on the axle end as explained in several of the other post. If you do one upper and use the poly, I'd still put it in the axle end.

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Thank you, you have been a big help.

One Upper: Solid joints all around (Johnny Joints, Superflex joints, heims, etc)

Two Uppers: Rubber or poly at the axle ends and where upper connects to lower, Solid joint (see above) at the frame end.

poly belongs on a parrots name tag, not on a Jeep.

You could try slicing some pool noodles into bushing size chunks.