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  #31  
Old May 4th, 2021, 09:56
Rob Mayercik's Avatar
Rob Mayercik Rob Mayercik is offline
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Re: Greaseable Shackle Bolts

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Originally Posted by RCP Phx View Post
On OEM bushings the center sleeve is not supposed to move, it's even bonded to it.
I think I think you've misunderstood the question I asked. Let me restate it to better explain where my head is at.

As the suspension compresses, the leaf spring flattens and "gets longer", causing the shackle to swing toward the rear bumper. This imparts some degree of rotational force onto the bushing and bolt in that eye of the spring. When the suspension droops, the spring "shortens" again and the shackle swings back toward the front of the vehicle

Unrelieved, this will cause the bushing to "wind up" like a torsion spring, which I assume is not an intended effect of cycling the suspension (in the same way that rotational stresses build up in a 231-equipped jeep operated in 4Hi on pavement where the wheels cannot slip).

Assuming that this "windup" effect is not part of the suspension design, there are only two ways that I can see to relieve it - either the bushing must rotate within the spring eye, or the bushing must rotate on the bolt.

Since the eyes in leaf packs do not normally come with grease fittings in them, I must therefore assume that the intention is for the bushing to be able to rotate freely on the bolt holding it to the shackle. The bolts we've been discussing in this thread support this conclusion, as they clearly are meant to supply lubrication to the space between the bolt and the inside of the sleeve.

With a urethane bushing, the sleeve looks (to my eye based on pictures) to have been made via extrusion - no seam, and perfectly cylindrical. Slipped onto a bolt in the hand, it seems like it should rotate quite freely. Not having handled any of this type, I don't know if the sleeves rotate in the urethane or not.

The sleeves in the OEM rubber bushings, based on the Clevites I used when I replaced my leaf packs several years ago, looked different. They appear to have been made by taking a flat piece of metal and bending it around a template - I could see where the two "sides" of that piece were brought together. When I slid a bolt into those bushings, I basically could not rotate the bushing at all on the bolt. This would explain why maxbraketorque reports delamination in his rubber bushings - the formed sleeves simply cannot rotate freely like the extruded ones found in urethane can.

My question was whether the binding of the bolt in the formed sleeves of OEM-style rubber bushings is supposed to occur, or if it's a sign of a manufacturing issue and they are supposed to spin freely as well.
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  #32  
Old May 4th, 2021, 10:51
maxbraketorque maxbraketorque is online now
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Re: Greaseable Shackle Bolts

Rubber bushings are bonded to the inner and outer sleeves, and therefore, the rubber is meant to twist / wind up like a torsion spring. It is bonded to prevent the leaf spring from sliding sideways on the sleeve or on the spring. Urethane bushings are fundamentally different in that the bushing spins on the sleeve. To prevent the spring from moving sideways, a lip is added to each side of the bushing that acts as meat between the spring and the shackle.
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  #33  
Old May 4th, 2021, 10:58
RCP Phx RCP Phx is offline
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Re: Greaseable Shackle Bolts

I can only "assume" but the FSM states to lower the weight onto the vehicle before tightening the bolts, and with really high torque values(they vary) there is not much chance they intended on the sleeve being able to rotate.
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  #34  
Old May 4th, 2021, 20:55
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Re: Greaseable Shackle Bolts

.. and Mike at MORE told me that he recommends only 35# torque on spring bolts SO they
WILL spin (talking TJ but shouldn't matter). I mentioned that OEM spec is 85# (or so) and he thought that would defeat the intended function.
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  #35  
Old May 5th, 2021, 07:51
RCP Phx RCP Phx is offline
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Re: Greaseable Shackle Bolts

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Originally Posted by NOTNSUV View Post
.. and Mike at MORE told me that he recommends only 35# torque on spring bolts SO they
WILL spin (talking TJ but shouldn't matter). I mentioned that OEM spec is 85# (or so) and he thought that would defeat the intended function.
That's horrible advice. Most of the OEM bushings I seen have a serrated edge on the sleeves that would cut into the XJ uni-body in a heartbeat!
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  #36  
Old May 5th, 2021, 08:29
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Re: Greaseable Shackle Bolts

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Originally Posted by RCP Phx View Post
That's horrible advice. Most of the OEM bushings I seen have a serrated edge on the sleeves that would cut into the XJ uni-body in a heartbeat!
I always hesitate to stray from factory specs and this seemed to be an odd one.
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  #37  
Old May 5th, 2021, 09:27
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Rob Mayercik Rob Mayercik is offline
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Re: Greaseable Shackle Bolts

Quote:
Originally Posted by maxbraketorque View Post
Rubber bushings are bonded to the inner and outer sleeves, and therefore, the rubber is meant to twist / wind up like a torsion spring. It is bonded to prevent the leaf spring from sliding sideways on the sleeve or on the spring. Urethane bushings are fundamentally different in that the bushing spins on the sleeve. To prevent the spring from moving sideways, a lip is added to each side of the bushing that acts as meat between the spring and the shackle.
thanks for clarifying. I learned something today.

Tha
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