Leaf Spring Relocation Kit

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dart67

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I just got a US Car Tool leaf spring relocation kit for my 74 duster,when I was looking at the rear shackles I noticed where a hole has to be enlarged there is a bolt going into the hole for the rear shock for the bumper, has anyone ran into this and what did they do?
Thanks
 
RogerRamRod, If I read your post right the new brackets bolts to the existing bolt hole on the frame, if that is right that's where my shackle bolt goes thru with the relocation kit
Thanks
 
RogerRamRod, If I read your post right the new brackets bolts to the existing bolt hole on the frame, if that is right that's where my shackle bolt goes thru with the relocation kit
Thanks
I think 72 was saying he could have gotten by without those brackets. I did see that though, after I reread his postings. And unless you have a traction problem, the idea of shedding 100+ pounds off the back your car could be helpful.
 
Yeah you don't need the brackets I added if you weld a patch panel into the hole in the rear panel where the shock mount goes through. That's what I'll be doing the next time the bumper comes off, just a 16 or 18 gauge patch and maybe a small 90* bracket from the patch to the frame rail to back up the original bumper bracket. That would leave the original shock mount hole open for a shackle mount.
 
Ok thanks everyone for your help
 
I used the offset kit fron dr Diff and welded a larger diameter tube in factory holder to accept larger bushings. Was this what your doing or are you going to center of the frame?

2ry4y0p.jpg


2ry4y0p.jpg
 
Going to the center of the frame
 
I used the offset kit fron dr Diff and welded a larger diameter tube in factory holder to accept larger bushings. Was this what your doing or are you going to center of the frame?

That's an offset kit. He's doing a spring relocation, so the 3" move to the frame rails. Just FYI, you can use Energy suspension 2-2117G bushings for A-body shackles. They have the correct 1/2' bolt diameter and larger 1" OD for aftermarket, SS and mopar performance springs.
 
Also, here's some more pictures of the early bumper modification to clarify what I said. Here's what a '74 with a rear shock bumper looks like at the rear panel

IMG_5227_zps7702bd3e.jpg


You can see the large "D" shaped holes for the shock mounts

Here's an earlier rear panel. This one's a demon, but it doesn't matter.
s-l1600 copy.jpg


The smaller outer holes are actually the ones you need for the early bumper brackets. The outer one is actually still behind the outer panel on the later cars
IMG_5231_zpsa80af90a.jpg

So you can drill that one out and use it to locate the other hole. The problem is it falls into the middle of the "D" shaped hole on the later shock mount bumper cars. That's where I made the bracket, but what I should have done was just make a "D" shaped patch out of 16 gauge metal and weld it in.

Here you can see how the bolt for the early bumper bracket falls into the middle of the "D" shaped hole, and the bracket I made. But if you just weld up the hole you wouldn't need the bracket. Or you could just use an "L" bracket and weld it to the end of the frame rail to make the mount stronger, like if you wanted to actually use a bumper jack.
IMG_5237_zps5212332c.jpg


I'm kinda surprised I haven't seen this brought up before, apparently not a lot of folks do the 3" relocation on shock mount bumper cars.

Here's another way, YoungGun2.0 used spring sliders. He recessed his up into the frame, but I don't think that would be necessary. You should be able to keep the car at about the same ride height if you just mounted the sliders to the bottom of the frame rail. He moved his up a little to lower the car. His is post #7.

Rear Leaf Relocation Kit pics

This is how he did it
sliders027.jpg


But I think this would work just fine, you'd just have to figure out how to weld a few nuts into the frame to bolt the bracket to. Or weld the slider to the frame rail, but then it's a little harder to remove it later. If you did this, you'd just have to buy the spring sliders instead of converting the entire rear bumper because you should be able to leave the shock mounts in place.
sliders001.jpg


The car would be lowered a little less than 3/8" with them mounted like this ( I used spring sliders bolted to the bottom of the frame of my car, but at the 1/2" relocation mark not under the frame rail).
IMG_2566_zpsvhkdudkp.jpg

IMG_2580_zpsuuetr2gp.jpg
 
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Spring relocation reduces the effective spring rate in the rear, because the spring is working against a shorter axle lever arm, and therefore has less leverage than it had when it was in the stock position. The lower spring rate changes the handling quite a bit for the worse, IMHO. I think it is necessary to correct for this. I'm not a suspension expert, so I will leave it to others to perhaps discuss this further.
 
Spring relocation reduces the effective spring rate in the rear, because the spring is working against a shorter axle lever arm, and therefore has less leverage than it had when it was in the stock position. The lower spring rate changes the handling quite a bit for the worse, IMHO. I think it is necessary to correct for this. I'm not a suspension expert, so I will leave it to others to perhaps discuss this further.

This is true. Moving the springs any amount inboard increases the lever arm between the center of the contact patch and the spring by that amount, so, the wheel rate is effictively changed. A greater force is applied to the spring. The further the springs are moved, the more force is applied. So, the spring rate has to be increased to compensate. For a 1/2" offset the difference is minimal. For the 3" relocation the difference is more significant. But higher rate leaf springs are easily obtained, and the factory rear spring rate wasn't as far off as the spring rate of the torsion bars in the front. A lot of these cars actually end up tail happy (loose, in oversteer mode) with just the addition of a rear sway bar, so it's not that big of a deal. A larger rear sway bar can be used to correct the roll stiffness. I run an E-body rear sway bar on my car with a 1/2" offset, so does 72bbswinger and his springs are relocated 3". It's one of the reasons I only went to a 1/2" offset, but with a Duster I can fit 295's with just the 1/2" offset, so that was a consideration too. I don't need any more tire than that anyway.

It's something to consider, especially if you're looking at autoX or road racing, but it's not at all difficult to deal with.
 
72BluNBlu, I would have thought that moving the springs inward would reduce the spring rate, but I may not know what I am talking about!
 
72BluNBlu, I would have thought that moving the springs inward would reduce the spring rate, but I may not know what I am talking about!

It reduces the effective wheel rate, but that happens because the force applied on the springs increases. You need to increase the spring rate to match the increased force transmitted from the wheels.

Don't confuse wheel rate and spring rate. Moving the springs does nothing to change the spring rate, it's the same. The springs don't care. But the effective wheel rate changes, because the length of the lever arm changed between the wheel and the spring.

So, the relocation lowers the effective wheel rate compared to the stock spring location for a given spring. To compensate, you need stiffer springs. Or a bigger sway bar. Or both.
 
@72bluNblu... I found this discussion from several years ago, but always relevant i guess. My 71 Demon will have a 3" spring relocation. It will be mostly street driven, with some time on the open track/autocross as well. I was planning on using the Hotchkiss leafs, but curious if you'd suggest something better considering the wheel rate discussion above? Will have Hotchkiss 1.5 shocks as well and some sort of rear sway bar. Thanks
 
@72bluNblu... I found this discussion from several years ago, but always relevant i guess. My 71 Demon will have a 3" spring relocation. It will be mostly street driven, with some time on the open track/autocross as well. I was planning on using the Hotchkiss leafs, but curious if you'd suggest something better considering the wheel rate discussion above? Will have Hotchkiss 1.5 shocks as well and some sort of rear sway bar. Thanks
Did you ever end up running the hotchkis springs 3” inboard with their sway bar?
How did it work out? My demon already has 3” inboard SS leafs but I’d like to make it handle better.
 
Did you ever end up running the hotchkis springs 3” inboard with their sway bar?
How did it work out? My demon already has 3” inboard SS leafs but I’d like to make it handle better.
I am running the Hotchkis sport springs inboard 3" with a Hellwig rear sway bar. The a-body bar won't fit... I believe it was the e-body rear bar that worked for me.
 
Something like the Helwig HEL-6908?

Thanks man I appreciate it.

Exactly like the 6908

I use one with a 1/2” spring offset, but it actually works better with the 3” relocation.

72BBSwinger ran exactly that on his car, you can see his mounting arrangement with the 3” relocation for the 6908 here

007-jpg-jpg.1716235637
 
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