Greasable shackles
Greasable shackles
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CJ
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If you use poly bushing shackles, greasable is nice. If you run standard rubber bushings, they are not needed - IMO.
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I've never used greaseable shackles but they make me wonder. They can't be as strong as a regular shackle. They have a hole down the middle of the shackle bolts. I guess they are strong enough but that's an assumption.
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The hole is so small I can't think it is any weaker plus it is full of grease. IMO
73CJ
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Not a big deal to drill Grade8 bolts if you have access to a lathe. There several places on the Net that sells them too. The strength lost is quite small if you run the numbers because it is on the center axis. Shear loss is minimal due to the small square inches of material lost. A 1/16" hole in a 7/16 bolt is .003 square inches removed from .AMC 150 square inches of bolt = 2% less. ( 2.7% for a 3/8" bolt)
Shear on one corner of a CJ is approx 27,000 pounds of force per 7/16" bolt. For a 3/8" bolt it is 19,878 pounds of force. Bottom line - you're not going to shear a bolt. (125,000 psi for a grade 8 bolt and it is in double shear)
The spring mounts can be drilled and a zerk added.
Keeps them from squeaking.
Shear on one corner of a CJ is approx 27,000 pounds of force per 7/16" bolt. For a 3/8" bolt it is 19,878 pounds of force. Bottom line - you're not going to shear a bolt. (125,000 psi for a grade 8 bolt and it is in double shear)
The spring mounts can be drilled and a zerk added.
Keeps them from squeaking.
Last edited:
PaRenegade
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I'd have to agree. Just like a structural beam for a house the center axis sees the least stress forces. The top is in compression while the bottom is in tension. This is also how I-joists work. The top and bottom chord is a thicker, usually LVL type material, while the center is a thinner plywood or OSB. You can drill the center of joists but never drill near the top or bottom edges.
But to the original question, no, they are not a hoax. Spring mounts and shackles are all "pivot" points. The bushings provide a "bearing" of sorts so that everything can move while still remaining tight and fairly solid. The grease provides a thin film of lubricant between those moving surfaces, just as a bearing does. And less friction makes less noise as well. It also makes things easier to get apart!
But to the original question, no, they are not a hoax. Spring mounts and shackles are all "pivot" points. The bushings provide a "bearing" of sorts so that everything can move while still remaining tight and fairly solid. The grease provides a thin film of lubricant between those moving surfaces, just as a bearing does. And less friction makes less noise as well. It also makes things easier to get apart!
jeffgtoman
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I agree. The issue isn't "greasable shackles". It's "what bushings do I want to run?" Poly bushings are stiffer but they can squeak when dry. They don't give. They rub. Rubber bushings dont move around. They bond to the metal and give or twist in the middle.
I like the fact that everyone so far has given you good info without arguing. I hate it when a post starts a rant between people that don't agree and feel the need to be right.