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Old 02-09-2020, 01:34 PM
Rusty76 Rusty76 is offline
232 I6
Join Date: Jul 15, 2018
Location: Cochrane
Posts: 225
Simple leaf/shackle question

Can someone explain something simple to a simple guy!
Replacing my rear leafs with a 3 inch lift spring. I also need to relocate the shackle hanger. I started to wonder what keeps the jeep from just dropping and having that shackle parallel to the ground. I get that I want my shackle angle less than 90 pointed towards the back but how does it stay at that angle? You need movement in the shackle to do its thing as the wheel comes up but why does it stay like that?
Shouldn't it always just drop to parallel when weighted. (wheels on the ground)..
I know its a simple answer but I just don't get it!

Thanks! Hope everyone had a nice weekend
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Old 02-09-2020, 01:42 PM
Rusty76 Rusty76 is offline
232 I6
Join Date: Jul 15, 2018
Location: Cochrane
Posts: 225
I ruled out magic
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Old 02-09-2020, 11:26 PM
SJTD SJTD is offline
350 Buick
Join Date: Apr 26, 2012
Location: Lompoc and Sunland, CA
Posts: 1,406
The spring still has to compress for the shackle to move back.

The shackle angle does affect spring rate. Having the shackle above the spring and pointing back (on the rears) gives a somewhat softer ride due to the leverage effect you're thinking of.

If they were angled forward it would be stiffer since the weight wants to move the shackle forward against the spring which wants to get longer and move the shackle back.

This assumes the shackle is above the spring, not the stock configuration which is what I think you're asking about.

If the shackle is below the spring the effect is opposite. If it's angled forward at rest compressing the spring moves the shackle back in the direction wheel movement wants it to go. If it were angled back the weight of the vehicle would move the shackle forward while the lengthening spring would want to move it back.
Sic friatur crustulum

'84 GW with Nissan SD33T, early Chev NV4500, 300, narrowed Ford reverse 44, narrowed Ford 60, SOA/reversed shackle in fornt, lowered mount/flipped shackle in rear.
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Old 02-18-2020, 07:00 AM
rocklaurence rocklaurence is offline
Join Date: Jan 14, 2009
Location: 33812, Lakeland, Fl
Posts: 1,720
Simple answer is the distance from the spring mount to the shackle pivot is a set amount [45"]. However, the spring is Arched [half circle] and the distance between the two spring mount holes varies from [42-47"] as it relaxes or compresses under the vehicle. So, the position of the end of the spring relative to the shackle is always moving forward and backward as the Arch in the spring changes. The arch in the spring is the force that prevents the shackle from extending to horizontal. Lastly, when the spring is flat it is the longest relative to the permanent mount.
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Old 02-18-2020, 11:13 AM
Rusty76 Rusty76 is offline
232 I6
Join Date: Jul 15, 2018
Location: Cochrane
Posts: 225
Hi Guys: Thanks for taking the time to answer this question. I had a hard time trying to phase what I was talking about. Both very helpful responses.

I guess another way to think about it is the body of the vehicle is being help up by the arch. Specifically the part that bolts onto the axle and forward to the fixed point that bolts to the frame?
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