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Rear springs relocation ??

13544 Views 24 Replies 12 Participants Last post by  vitamindart
I started moving my springs into the frame rails. Planned on doing it as per the tech article.  Once I got my rear out and springs out I got to looking at everything.  Wouldn't it be easier and better to make brackets for the front and mount the springs on the inside of the frame rails?  For the rear all I have to do is put a piece of box tubing in between the frame rails and weld the rear spring mount to that.  To me it seems better than cutting my frame rails.  Am I missing something here?  I don't want to start doing it this way and then find a problem I never thought of before.  So I thought I'd ask you guys first.

I forgot to add that this is on a 74 duster and will be used as a drag car only. Fuel cell in trunk, so I won't have the factory gas tank to worry about.

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There was actually a kit that allowed the very type of spring relocation you're describing.
it's pretty easy
Hi 70runner, I'm relocating the springs on my 67 barracuda right now myself. The process you are describing is used by many and it probably is easier. I'm going to cut the frame on my barracuda and here is why. On a hotchkis type suspension all of the thrust is on the front of the leaf spring. It needs to be solid and strong. It should also ,ultimately, line up laterally with the front frame rails( my point of view). Subframe connectors are going to help but should line up laterally with the front frame rails (everything helps) Also what is this going to do to your roll center. I realize your duster is "drag race only" but you also have to keep it off of the guard rails. Happy trails, CharlieWhen engineering, there is always a trade off.

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For a mild bracket car i do them inside the frame. I myself dont like the mopar kit. And I dont like cutting up the frame right where the leafspring is trying to lift the car. Plus i think box in the mopar kit is way too thin. Seen several of them where the front leaf spring bolt enlongates the hole in the box. I built this 68 dart for a friend to bracket race.  I Did the springs inside the frame and it's the straightest running car i have ever driven. It has a mild 360/904 and runs low 11's and will almost hook without a burnout.  It's won 3 NHRA "Wally" trophys in the past 2 years. I raced it once last year and won a $1700.00 winner take all race.  ;D ;D
Mopartranman, Looks like mono leafs on that Dart. I plan on using 3/16 tubing.Notice the piece laying on the floor under the barracuda. I thought the mopar kit looked wimpy also. Can you tell us more on how you build the brackets for the "inside the frame" reloction? I haven't cut the frame yet and am open for suggestions too. Charlie
It has the 002 & 003 superstock springs on it. Can see a few pics of the way i did the hangers at this link.,997.0.html
Thanks for the replys. I haven't decided which way I'm going to go with the rear spring relocation, but if I do go with cutting the frame rails I am going to use thicker metal and make my own boxes for the front springs to mount to. After reading the responses I do believe inside the frame would be easier but it will affect the roll center of the car, how much I don't know. I'm concerned if I ever get sideways the car may want to roll to one side too much and then when I try to steer out and the car comes back the other way it could really roll the body of the car thereby just creating a whipping effect and a complete out of control nightmare, at least until I hit the guardrail or worse yet the other car. This may not be a real valid concern as others have done it inside the frame rails and not had any problems.

Just thought I would thank you guys and let you know what I'm thinking.

I have one more wheel well to finish moving and then its decision time. o[

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mine i cut the frame didn't see the point of moving the springs in further as the frame is in the way of bigger tires witch is why we move the springs anyway , not saying there is anything wrong with moving them inside the frame
as far as the boxes i used the mopar ones already paid for them next time i will make my own and yes they would be thicker but i haven seen any problems with mine drove it on the street quite a bit and ran 10's with super stock springs
I have already move my springs into the frame. Its the first time I have done this type of modification to a frame. I also used the mopar kit. Would it help to reinforce the holes by welding washers like the artical shows doing on the rear mount?
Reinforcing might help. Accurateness of the hole size is of the utmost importance when drilling the hole for the spring location. Did you notice how hard it was to remove the spring bolt originally ? Drill size is not accurate enough. Reduce the drill size and then slowly (slowly!) increase the hole size with a die grinder with a carbide bit. Using the spring bolt ( new bolt ,right?) until it fits. It works for me. The original spring bracket may be harder than the mild iron stock I am using. I don't know. Softness of the iron we are using may be contributing to the elongation of the hole that MOPARTRAN is referring to. I think it has to do with the hole size. What do you think MOPARTRANS?
I just figured it was from the mopar boxes being thinner than the original front hanger. I would do something to reinforce them. Just my 2 cents worth.
I had to adjust my hole location in my boxes due to the factory geometry not being the same on both sides. So, I am using a washer to do this, which will add some strength.

As far as moving them inside the rails, it is probably easier, and will more than likely work fine. One thing though, the further you locate the springs towards the center of the car, the more unstable it will become. Might now be a huge deal with a drag only car, but if you want the car to handle at all, it might be worth thinking about.

I'm not trying to convince anyone to do it my way. If I was going to build a car to handle I would leave them where the factory put them. IMO, I'm more concerned on how the thin mopar boxes and the even thinner frame rails are flexing or trying to bend if the car got sideways. Seen cracks in the frame rails from the mopar kit flexing. The factory frame rails are just too thin to trust. I just bought a 69 dart a few months ago that already has the mopar kit in it. I will be cutting it back out and fixing the frame rails back. Then i will do it my way. I used 3/16" steel to build them inside the frame and i would trust it a 1000 times over the mopar kit. I built that purple dart for a friend of mine. So his son could bracket race. It runs 7.0's in the 1/8. And drives so straight and smooth you would think in the a 10 second street car. I invite any of you to call him before you cut up your frame rails and ask the guy about how his Son's car drives. PM me for his #. I wouldn't have built it for them if i thought it was unsafe. The holes i seen enlongate in the mopar boxes were in bracket cars. Those cars never left straight because of the rear end moving around. And a plus with the way i do it... I can build a new inner frame rail and do the tubs all the way to the original inner frame rail. Gives me room for a 13x31 slick easy.
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i drilled my holes in the boxes before they ever when under the car and the used a piece of 1/2 tubing from one stock mount to the other to locate the new boxes ( i had to cut a section of the frame out so the bar could go across but i never had any alinment issues later worked great for me i have thought about welding a washer on the outside of the box to reinforce it i also had a second hole a inch or so above the other worked out nice when i put the super stocks in and i could lower my car back to a stock style height
I wouldn't cut the frame unless I put a cage in.
I made my own boxes from 3/16 plate and bored the holes exactly 5/8. I can't see any issues with the holes in that material. I also will run my frame connector tubing right into the back of the hanger box. It looks like it will be very solid.
can anybody give me dimensions of the boxes cause i want to build my own. i feel the same way about the mopar ones being to thin
I want to do this but i dont know if i can. the rear frame rail whare you would weld in the new rear shackle is rusted out pretty good but the rest of my frame is good. I would have to cut out the bad and bulid up the frame back. dose anyone have this problem to. The place whare the factory rear shackle is is ok just whare i would need to put the relocated shackle.  Any ideas would help
I finished my wheel mini-tubs. I did it just like the tech article, everything went just like in the article. Thanks to bbdart and whoever wrote the article. I started on my relocation of the rear springs. I cut the frame rails and am doing it just like in the tech article on relocation of the springs. I used the Mopar boxes but I re-enforced the boxes a little. I am also going to add large washes to each side of the bolt that hold the front of the spring, weld the washers to the box. This should be plenty of re-enforcement to eliminate any chance of hammering the holes bigger in the future. Then when I weld in my frame connectors I am going to come all the way back to the new spring boxes I just put in. I won't know for sure for a while, but I think I am adding enough re-enforcement to eliminate any problems. I even thought of cutting the bottom out of the frame rail connector right where it would meet up with the spring boxes, leaving the sides, drilling holes for the spring bolt, then welding that solid to the boxes. I would end up with almost 1/2 inch of metal on each side of the spring boxes. I know that would be plenty. Probably overkill, but I really can't say "too much" when it comes to the safety end of it. I spent a least twice as much time laying under the car thinking about how I was going to do this, than I did actually doing the work. But I am pleased with how things are going so far.

Thanks to all for the responses.
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