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longer shackles?

kingmeirl

kingmeirl

NAXJA Forum User
Location
Cumming, GA
I have a rusty's 8" lift and the rear leafs are really curved (no blocks). My question is when I am going to change the shackle angle from almost 0 degrees to 45 degrees, wouldn't it also benefit me to make the shackles longer? longer shackles would allow the leafs to stretch all the way out for full flex, right? or am I wrong?
 
i believe the more angle u have the softer the ride, have u checked on shackle relocation brackets? i have them and it gave me about an inch in lift, but the shackle angle went from almost straght to 45 deg and improved the ride and flex greatly, they have them in the vendors forum. hth
 
I have looked at those, but I am not looking for any more lift, just more flex. Also, the way my leafs are so curved, I want to make the shackles longer. I am working out the geometry now to see how much longer I want them. Those brackets just change the angle. I am going to have to completely cut the originals out and make my own bracket much higher and farther forward than what those bolt in brackets could offer. but maybe I could use those and weld them where I want them?
 
ya, i bought the jeep this way (stock axles too!). They look to be aftermarket shackles (rusty's) but are bolted up in the stock location. They are 4 3/4" long and look to be at a 75 degree angle going the wrong way.
 
From the looks of the pics, won't the lower part of the shackle hit the bracket before full compression can be achieved?
 
i'd look at leaf if you want more flex. 4.5 in leafs, 1.5 u bolt elim. shackle relocation box and 1.5 lift shackles. should put u at the same lift and will flwx better then the 8" packs.

keep in mind that the angle of the shackles will effect your lift. (not much tho)
 
Did you look at more then the first page on the second link I gave you? There are pics on pgs. 2, 4, and 5 of rigs flexed out with theyre kit. Doesnt look they have any binding problems.

I would second what userbmx1315 said. Look in getting smaller leafs.
 
smaller as in flatter? how would flatter leafs flex more? I could understand less leafs so they would bend easier.
 
I see why the shackle at a 45 degree angle would allow for more flex, It takes less movement of the leaf to move the shackle up and down in relation to the vehicle at that angle. As opposed to the shackle being at 90 degrees, where the leaf would push the shackle horizontal to the vehicle. Basically, its easier to rotate the shackle than compresss the leaf.
 
The shackle angle should be 90º to the angle of the leaf. The angle of the shackle to the body is irrelevant. At 90º to the leaf, the movement of the leaf can be most effectively transferred into the shackle with minimum upward forces applied to the shackle (and thus, the body), giving both the smoothest ride and the greatest flex.

Of course, this isn't always possible, but in theory, that's your target. Most like to be a little past 90º so that on suspension droop, the shackle doesn't decide to push the wrong way and invert.
 
ok, so i've been doing a lot of geometry. Ride height the leaf is 49" bolt to bolt. The leaf flat would be 53" long. With my stock 80 degree (reversed) shackle that is 4.75 inches long, and the leaf flat, I would only have about 9 inches of travel up. If the same shackle were place in the 45 degree forward position, I would only have roughly 11 inches of travel up. I would also gain 2 inches of droop. Not saying I am going to do this, but the math shows that if I replace my 4.75 inch shackle with a 36" shackle and mount it at a 27 degree angle (forward of course) then I would have 16 inches of travel up and 16 inches of droop (from ride height). That is 8" from the leaf and 8" from the shackle. That is only if my leaf were flat. And these numbers will only apply to my same size leaf, but you get the idea.
 
TheAlmightySam said:
The shackle angle should be 90º to the angle of the leaf. The angle of the shackle to the body is irrelevant. At 90º to the leaf, the movement of the leaf can be most effectively transferred into the shackle with minimum upward forces applied to the shackle (and thus, the body), giving both the smoothest ride and the greatest flex.

Of course, this isn't always possible, but in theory, that's your target. Most like to be a little past 90º so that on suspension droop, the shackle doesn't decide to push the wrong way and invert.
Click to expand...

If the shackle were at 90 degrees to the leaf, then the leaf would have to push the shackle out before it pushed it up, which would negate the whole physics behind moving it in the first place, right? You want the shackle to move up with compression of the leaf, not out. And if it were at 90 degrees you would have almost no droop before the shackle was maxed out in that direction, or started inverting like you said.

I'm just trying to find the physics in a leaf and shackle and use it to our advantage instead of just doing what everyone else does. I'm really sorry if someone takes this wrong, but I just want to help.
 
kingmeirl said:
If the shackle were at 90 degrees to the leaf, then the leaf would have to push the shackle out before it pushed it up, which would negate the whole physics behind moving it in the first place, right? You want the shackle to move up with compression of the leaf, not out. And if it were at 90 degrees you would have almost no droop before the shackle was maxed out in that direction, or started inverting like you said.

I'm just trying to find the physics in a leaf and shackle and use it to our advantage instead of just doing what everyone else does. I'm really sorry if someone takes this wrong, but I just want to help.
Click to expand...

Why does it matter which direction the shackle is pushed? The goal is to allow the maximum fore-aft travel of the rear spring eye. When the spring is compressed, it will most easily transmit force to a shackle that is placed at a 90º angle to it.

Think back to physics class: Moment = F x r, where all three quantities are vectors. The greatest moment will occur when F and r are perpendicular to each other. Imagine a wrench on a bolt. By pushing purely in one direction on that bolt, as the leaf spring pushes purely in one direction on the shackle, it takes more force to push against a wrench that's in any position other than at a 90º angle to your arm. The same goes for the leaf spring.

Of course, as mentioned, this is not always practical. Knowing how much the rear eye will move forward during downtravel tells you if the shackle will reach the limit of its movement. Once the shackle and spring are colinear, of course, the spring can move no further.

So, ideally, 90º to the spring, but this is not always practical.
 
heres what my shackle angle looks like. dodge van main and an s10 bastard.
100_0010.jpg
 
I see what you are saying and you are right about the forces, but in the case of the leaf and shackle, you are not trying to just compress the leaf, you can also get up and down travel for the axle if the shackle moves in the same direction. So, if the shackle is at 90 degrees, and the leaf flattens the shackle will not travel up, it will travel horizontially. But if the shackle is at 45 degrees, and the leaf flattens, then the shackle will be forced to move up, giving you more travel which is what we are trying to accomplish.
 
untitled.jpg


A is the distance the leaf will travel when flattened
B is the direction the shackle will move when the leaf is flattened
C is the distance the leaf will move up when the shackle is rotated

A and C need be the greatest number for the greatest amount of 'flex'
B will change only when the shackle is repositioned or lengthened.

A will not change unless leafs are changed. If the shackle is at 90 degrees, C will be minimal. Notice how his shackle is at about 60 degrees. I would be willing to bet that he gets about 2 more inches of up travel than if his shackle were at 90 degrees.
 
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