leafspring shackle question

mpower

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ok , heres my question to all the leafspring gurus.

whats better? shackle over spring

or

shackle under spring

whats the benefits of each , pro's, con's , strength , ect.

im going to go sua on my truck and in oem form the shackle sits below the leafspring, rather unconventional to what i see on MOST of the leafsprung trucks out there. should i keep with the current design princeable , or change it to shackle over spring and why.

ive read a few books , searched all over the place and came up with the same questions . hoping the talent here can help me out
 

Captain Air Time

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I've never been able to feel the difference, but my brain insists that a shackle in tension (under) will be more stable than one in compression (above). Packaging and ride height also play a role. As for strength, a compression shackle can be mounted directy below the frame very easily (strong), with the pivot through, over, or under the frame member. in tension, unless the chassis is very tall, you generally are outboard of the frame(requires more bracketry). What fits seems more important, IME. Every time I contemplate changing to a different shackle, I end up drawing a 4-Link, which doesn't fit either :D
 

Triaged

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...shackle over spring or shackle under spring...
whats the benefits of each , pro's, con's , strength , ect.
The major difference is in the installed spring rate. Tension shackle will get stiffer in bump than compression shackle. As with everything leaf spring it is a bit more art than science. If you really need it I might be able to scan the page from the book for you.
 

Armistice

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Over you can get a longer shackle, 12", under, I think you're limited to 9"... but really depends I think. I'm doing a 12" over on my Tacoma when I get to it
 

mpower

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The major difference is in the installed spring rate. Tension shackle will get stiffer in bump than compression shackle. As with everything leaf spring it is a bit more art than science. If you really need it I might be able to scan the page from the book for you.
thanks that would be great , what book is it. theres not much on leafspring setups in some of the books i got

i like the fact that springrate increases with bump but does it have any drawback to how the spring rebounds in comparison to a compression shackle?

i guess next q would be how to properly setup a tension shackle? ive seen many posts on compression shackle setup but none on tension shackles
 

atomicjoe23

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Would it be possible for any of you guys to post up any pic's of these two types of shackles??? I'm not really sure that I know what you are talking about. . .I'm no leaf spring guru, but I didn't even know there were different types of shackles (other than what you see on the rock crawlers and general off-roaders. . .i.e. boomerang, reverse, extended, tow shackles, etc. . .)

Thanks!
 
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