Rear suspension upgrade help.

[Dor-Dor68!]

Hey Everyone,

Still gathering, but progressing on gathering all the parts for a front brakes, steering and suspension upgrade, but wanted to ask about the rear suspension.

Since im swapping everything in the front...im also thinking of upgrading the rear. Ive looked into getting a leaf spring relocation kit from USCT and welding it on there vs. The Doctordiff's offset shackles. But please let me know what your thoughts are. hopefully I can get a little wider tire on the rear with the relocation kit and not affecting any of the goals. I would like to put a 18x10 wheel in the rear.

So ive checked out the mopar performance super stock springs(3200lbs), but would like to hear from anyone thats using them or even the Hotchkis leaf springs with a 1" drop, and also the Calvert mono leafs, But any suggestions would be appreciated. The rear end will be a swapped to a Ford 8.8 with 373s.
The only thing is that im looking for a great stance on the car, aggressive, but not too low either. The Darts goal is to be a daily driver, canyon carver and hopefully some autoX in the near future.

For the relocation kit im looking at the USCT kit, and also considering adding the Calvert's leaf spring sliders....but not sure if they'll be a good fit with the relocation kit. Any other suggestions on the slider boxes???

I'll attach a picture of how the Dart currently sits and again I'll appreciate all and any suggestions, info or ideas....and or other parts you all recommend or suggest.

Hope everyone is doing great and thank you for your time.

 

[72bluNblu]

The Super Stock springs will not be what you want based on your goals. They'll raise the car in the back, and also be too stiff for good handling. They are also not the same side to side, to help hook while launching for drag racing, which is not what you want for corner carving.

The Hotchkis springs are a good choice for what you have planned, you can also leave out the front hanger which is what drops the car the extra 1" if they end up being too low. But you wouldn't use the front hanger with a 1/2" offset or 3" spring relocation anyway, so the Hotchkis springs would land the car closer to stock height.

For the wheels, a Dart can pretty much only take a 255 with the stock spring locations. With the 1/2" spring offset like DoctorDiff's, or the one from @BergmanAutoCraft that does the 1/2" offset and adds spring sliders (BAC A Body Leaf Spring Relocation Kit – Bergman Auto Craft ), you can still only get to a max of a 275 rear tire, which would work on an 18x10 but I don't think that would be your best option honestly with only the amount of room you'd have in the stock wheelhouses. You'd be better off with a 275 on an 18x9 or 9.5, even though that's on the small side for the recommended range.

To go any larger than 275 in the back you'd need the full 3" relocation and mini-tub. I believe the USCT kit includes everything to do both, but just for information doing the 3" relocation on the springs doesn't help you at all if you don't do the mini-tub, because a 275 is all that's going to fit in the stock wheelhouse and even that will usually take some quarter lip trimming/rolling.

If you do the full UCST 3" relocation and mini-tub, well, you can get 335's in there if you want.

I have my Duster set up in similar fashion, I run 1.12" torsion bars in the front, Hellwig sway bars front and rear, I run a discontinued AFCO rear leaf spring with a 1/2" offset and spring sliders with homemade brackets. Duster's have an extra 1" of space in the stock wheel wells and I run 295/40/18's on 18x10's in the back and 275/35/18's on 18x9's in the front.

My build thread is in my signature, it covers most of everything in my build although it is a bit long at this point

 

[Dor-Dor68!]

Thank you so much yet again @72bluNblu,

I really do appreciate your input and help...

So I'll be aiming to get the Hotchkis 1" drop rear leafs and the USCT relocation kit, but now that u helped clarified how to get wider tires, I'll probably get the kit with the mini-tub. But also depending on the budget, I might just get the 3" relocation kit without the tub.
Do you have any recommendations or how do u feel about adding slider boxes along with the relocation kit?? And any bushings suggestions, solid or poly?

I'll read and go through your build set up on ur page and get some more ideas.


Again, thank you so much for your input...and if its alright with u, I'll DM u in the near future if I have questions.

Have a great rest of your weekend and stay safe.

 

[72bluNblu]

There's really no point in doing all the work for the 3" spring relocation without the mini tub. The problem is that the stock wheel tubs are, at best, 12" wide on a Dart, some are a little less depending on the quarter lip. Most 275's have a section width of ~11". So right off the bat, a 275 wide tire is the biggest you can do with the stock wheel tubs, and that still requires it to be located VERY well in the space. That's also why the 18x10's are a bad idea with stock wheel tubs, an 18x10" is actually 11" wide outside lip to outside lip. So, very little clearance to work with on a 12" wide tub.

A 1/2" offset, like DoctorDiff's or BergmanAutocraft's, move the springs enough that the tub is the limiting factor, not the springs. I have a 1/2 offset kit installed in my Duster, the tubs are the inside limit on the tires, not the springs. I have rubbed the inside of the tubs with my 295's before I added the rear sway bar and later spaced the tires out a bit further by going to disk brakes. But the spring to tire clearance was never a problem.

And with the 1/2" offset kits the only thing you need to move is the spring perches (which you're doing anyway with the 8.8). The rest of the kit just bolts in, no cutting or frame rails, no making sure everything is straight and square and aligned properly. And, having the springs wider is better for handling. There are ways to deal with that, running substantially wider tires helps, but if you do the 3" relocation without the mini-tub you're just doing a ton of work, taking the detriment of having narrower springs, and not being able to take advantage of actually running wider tires.

As for the spring sliders they can be used with a 3" relocation, no problems there. You can basically just attach them to the bottom of the frame rails in the back. You could weld a threaded backing plate into the rails and bolt them on, or you could do something like @younggun2.0 did which was notch and gusset the rails and weld the sliders in. He did that to lower the car further, although just using the sliders lowers the car some already vs shackles. Here's his install Post your wheel and tire combos.

Feel free to DM me if you'd like, I'm happy to answer any questions I can