Rear leaf spring Question 74 Dart

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George Lawicki

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Hi guys,

Replacing my rear leaf springs with new ones from General Spring. I saw that there is an option to add and extra leaf if i wanted. I have read that others have added the extra leaf to improve handling but came with a stiffer ride. I am unsure as to the pros cons of doing so. The car is stock 6cyl and just looking to use it as a summer driver until I get into the restoration. So I don't want a ride like a truck but I also don't want that sway. Any help is much appreciated
 
I don't believe there's any way to answer that. You could order them +1 and make sure you are set up to pull it out if necessary. No way to know what the new springs are like

I rebuilt mine from old springs. Took the original 67 packs apart and took another set apart, put them back together using the longest leafs from both packs +1 spring. The turned out exactly right for me, but I didn't know that when I put them together. They are however somewhat firm, which I like

I'll tell you one thing.......you darn sure don't want the stock factory "floppy" ride they CAME with LOLOL
 
I added one leaf to my 72 dart and was pleased with the look AND feel. No noticeable harsh ride.
 
How many a-bodys have you seen with a real sag in the @ss end? You should be able to get 6 leaf springs like came new on 340 cars - like above, no noticeable harshness to ride. If you get it with one inch added ride height then after a year or so it will settle down to new stock ride height and stay that way for a long time...
 
I'm going with 6 leafs on my 75 dart. My dart had a really bad sag to it so I changed the leafs with factory replacement 5 leafs and it didnt help anything the sag was still there. So I added shackles to bring the rear up. (Yes I know it's a horrible thing to do but I was young and didnt know any better back then) so now I'm going with the 6 leafs from general spring.
 
An extra lead won’t have the car ride like a truck.
Sway is the lack of or an inferior anti roll bar. Install them as a set.
 
How many a-bodys have you seen with a real sag in the @ss end? You should be able to get 6 leaf springs like came new on 340 cars - like above, no noticeable harshness to ride. If you get it with one inch added ride height then after a year or so it will settle down to new stock ride height and stay that way for a long time...

Aren't you cute with your red X ? As if I'm not allowed my opinion ?

The A-bodys you see sag, because they have 50yr old springs !

To the original poster. Go ahead and add a leaf on your new springs, and I will be ready for your next post. "How do I lower my car with new springs, because the *** end sits to high".
Good luck !
 
Adding a leaf increases the spring rate of the spring. In my circle track days we'd add or subtract a leaf on one side to tighten or loosen corner handling. If your ride is basically stock, save your money until you know what you want. A stiffer spring in the rear will affect overall handling compared to stock. You may like it what it does, you may not.
 
Seems like there's a few terms/properties being interchanged that aren't interchangeable. Spring rate and spring arch are not the same thing.

Leaf springs sag as they get old. The arch changes, and the ride height gets lower. The spring rate, however, does not significantly change. That's important. The spring rate is a property inherent in the metal used. So your old, worn out saggy springs have a spring rate that's almost identical to what they were originally. The only reason it's different at all is because of the construction of the spring- the clamps loosen, the slide cushions between the leafs break down, etc. For the ride, the biggest changes that you notice with the "floppy ride" are mostly worn out bushings and contacting the bump stops because of the loss of ride height.

The spring rate is what you want to pay attention to. Somewhere I have the breakdown of the spring rates, but this is what they are for A-bodies and most of the available options

stock 5 leaf - 90 lbin (/6 and base 318 cars)
6 leaf "XHD"- 110 lb/in (340 cars and some upgraded 318 cars)
Mopar oval tracks- 120 lb/in
Hotchkis handling- 130 lb/in
Super Stock 002/003- 160 lb/in

The spring arch is what really controls the ride height. Adding a leaf mostly changes the spring rate. If you add a leaf without changing the arch you do end up with a little more ride height, but that's because you have a higher rate so the compressed arch of the spring is higher. The free arch is the same.

Hi guys,

Replacing my rear leaf springs with new ones from General Spring. I saw that there is an option to add and extra leaf if i wanted. I have read that others have added the extra leaf to improve handling but came with a stiffer ride. I am unsure as to the pros cons of doing so. The car is stock 6cyl and just looking to use it as a summer driver until I get into the restoration. So I don't want a ride like a truck but I also don't want that sway. Any help is much appreciated

What you need to find out is the spring rate of the springs you're buying. The construction can be totally different. If they just "add a leaf" to the 5 leaf spring pack you'll end up with a higher spring rate and a little higher ride height. But there's nothing that says that's what they have to do, their "5 leaf springs" and their "6 leaf springs" could have totally different construction- different leaf thicknesses, different arches, etc that could totally change things. More than likely that isn't the case, but if you don't ask you're just assuming.

The factory 5 leaf springs (90 lb/in) are pretty soft, and the factory ride height with them was actually pretty low to start off with. Even the original promotional advertising shows a lot of cars sitting dead level or even a touch nose high. The factory "XHD" springs, which had 6 leafs and a 110 lb/in rate are a nice upgrade if you have the factory 5 leaf springs. The ride is not too stiff, the handling will be improved and the rear end will be slightly higher. Even most of the aftermarket springs intended for good handling are only in the 120-130 lb/in range, which doesn't lead to the car "handling like a truck". They're noticeable firmer, but not crazy as long as you have decent shocks (not KYB's!). The SS springs are like 160 lb/in and while they definitely help launch they absolutely ride like a truck.

Mopar Performance springs as of late have been all over the place for quality. Even the XHD's I put on my Challenger like 8 years ago were made in Mexico and sagged significantly. The spring rate was good, but the car ended up pretty low after 6 months. Fine by me, but not everyone wants their car in the weeds. So I would avoid them unfortunately, because the MP oval tracks make for a great spring if the quality is good.
 
The more leaf springs the better. You can never have too much of a good thing.
:thumbsup:
 
Have you looked into having your old springs re arched?

Most semi truck shops will do it for cheep.
Call aroumd to heavy truck equipment / repar shops and ask.

I had custom U bolts made at a truck repar shop here in Ca for dirt cheep. They also re arch springs. I know the shop i used is to far away for you but in Ohio i bet there is some place near you that works on heavy trucks?
 
Here are the springs I am looking at from General Spring. I can get an extra leaf added if I want. I am going to be running stock 14" tires and rims. I am really looking for a nice good ride and better than stock ride/handling, as the car is going to be a summer driver. I don't mind a very very VERY slight higher stance in the back but no serious rake. Just a nice sitting car with a nice stance.

Springs.JPG
 
Here are the springs I am looking at from General Spring. I can get an extra leaf added if I want. I am going to be running stock 14" tires and rims. I am really looking for a nice good ride and better than stock ride/handling, as the car is going to be a summer driver. I don't mind a very very VERY slight higher stance in the back but no serious rake. Just a nice sitting car.

View attachment 1715485159

If the spring rate on the 5 leaf springs is only 85 lb/in I’d definitely get the 6 leaf version.

Both versions will sit higher than your current springs. The 6 leaf springs will probably sit a little higher than the 5 leafs, but it shouldn’t be much.
 
Here is the spring rate of the 6 leaf if it helps.

View attachment 1715485167

I run 120 lb/in springs on my Duster and have been happy with them. Full disclosure, my Duster is set up more for AutoX than the summer driving you’re talking about.

That said, I run a large rear sway bar because the 120 lb/in springs are still on the soft side for how my car is set up.

Between the 85 lb/in springs and the 120 lb/in springs I’d run the 120 lb/in springs. They’re probably at the upper end of the spring rate you’d want to run on your car based on your description of its use, but they should be fine.
 
Thank you all for the comments and advice. I think I will go and try the 6 leaf. now to figure out what size tires to run :p
 
What wheels are you using, what are the current tires and how much clearance do those have? you'll want to put the new springs on BEFORE you answer those questions because the clearances will probably change.
 
What wheels are you using, what are the current tires and how much clearance do those have? you'll want to put the new springs on BEFORE you answer those questions because the clearances will probably change.
Why would his tire clearance change because of new leaf springs?? Maybe the height but the width shouldn't be any different.
 
Dartfreak75 ; yep that's it, with the very limited room in the wheelwell of a 2 door hardtop, mostly the low top lip of the outward opening, an inch or two in ride height can make a big difference (also an arguement for a higher spring rate).
 
Dartfreak75 ; yep that's it, with the very limited room in the wheelwell of a 2 door hardtop, mostly the low top lip of the outward opening, an inch or two in ride height can make a big difference (also an arguement for a higher spring rate).
I understand what you are saying but I dont think the ride height is gonna affect the clearance if the lip is gonna rub the sidewalls it would rub no matter the height but I may be wrong.
 
On a Duster/Demon/Dart Sport or even a Barracuda the ride height can make a big difference because of the high wheel opening. Raise the car a couple inches and you can hang all the rubber outside of the quarter, doesn’t even matter what fits inside the wheel well.

On a hardtop Dart unless you put a 6” lift on it you’ll still be dealing with that low wheel opening for tire clearance.
 
Well that leads me to the question about tires next... I believe these are 100% stock 14" s that came with the car. SOOOO. what size tire combos can I run? For now, I would like to clean up and use these rims. What size tires will fit and look decent and not soo puny. lol

IMG_20200312_160017.jpg


IMG_20200312_160032.jpg


IMG_20200312_155843.jpg
 
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Not much... You can check but I think they are 4 1/2 inch wide rims. If so you could do some 205-70-14s.
The easiest thing to do is find a set of factory 14 inch big bolt rallye wheels. They are 6 inches wide and open up a lot more possibilities. You might be able to find a set of used 14x6 inch wide steelies like you have that would take your factory hub caps, but make sure they are straight by taking the bare wheels to a tire shop and have them spin them on a balancer and check for straightness.
 
What rim /tire choices if I step up to a 15" or 16" rim? I was looking at the 15 " rallys or mabe something like this

R!.JPG


r2.JPG
 
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