HD leaf springs vs. Standard for handling

Rusty knuckles

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69 charger with a 383. I think my leaf springs are worn out and I've been looking for a new set. My intent is a nice handling car. I'm not an autocross racer but I do enjoy the twisty mountain roads here. So my frame of mind is to do nothing that isn't an improvement in handling. I have a 7/8 rear sway bar installed and intend to install a front bar and bigger torsion bars this spring.

So back to leaf springs. I was thinking of upgrading to the HD leaves found in R/T chargers. However where they have 6 leafs on one side and 7 on the other they seem to be set up for drag racing. But looking at specs on both they have the same spring rates and same total capacity. So what am I missing here? I have zero need for a drag race suspension setup. Any suggestions?
 

66Satellite47

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The added leaf on the passenger side accounts for the natural torque of the axle and driveshaft. The Mopar XHD package (in the old days) was very good for general HP cruising. Otherwise call Springs & Things (ESPO). they have excellent leaf packages for a B Body.
 

Kern Dog

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You may find that with stiffer leaf springs, that 7/8” rear sway bar is too much. I had that setup and the car wanted to kick the tail end out in abrupt turns. FUN if you want it, ANNOYING if you don’t.
The condition is called oversteer.
I swapped in a 3/4” rear bar from an ‘83 Imperial. I have the Mopar Performance XHD leaf spring set with 2 RH sides.
 

Mr. Cranky

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You have a 7/8" bar on the back and no bar on the front or does it have the stock bar on the front? And I'm with Greg about having too large of a bar on the back vs the front can make it tail happy. Also, you can go with not so heavy springs and go with bigger sway bars that way it'll still ride decent in a straight line but will handle good in the turns....and of course with wider wheels and tires always helps.
 

66Satellite47

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You may find that with stiffer leaf springs, that 7/8” rear sway bar is too much. I had that setup and the car wanted to kick the tail end out in abrupt turns. FUN if you want it, ANNOYING if you don’t.
The condition is called oversteer.
I swapped in a 3/4” rear bar from an ‘83 Imperial. I have the Mopar Performance XHD leaf spring set with 2 RH sides.

Kern, I like the idea of passenger side XHD's on both sides. Shock and sway bar tuning is way beyond me.
 

Rusty knuckles

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You have a 7/8" bar on the back and no bar on the front or does it have the stock bar on the front? And I'm with Greg about having too large of a bar on the back vs the front can make it tail happy. Also, you can go with not so heavy springs and go with bigger sway bars that way it'll still ride decent in a straight line but will handle good in the turns....and of course with wider wheels and tires always helps.
Currently no front bar. It had one at one time but not since I've owned it. Installed the rear this winter and have only driven it once this way yesterday because i was curious. Took it to a open lot and did a little slalom and skid pad playing around. Nothing formal. Just jerking it around. Im certain its quite loose at higher speeds if i push it. Be good for drifting at the local drift events lol. Plan is for 1-1/8" front bar and 1.03 torsion bars from PST.
 

Rusty knuckles

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You may find that with stiffer leaf springs, that 7/8” rear sway bar is too much. I had that setup and the car wanted to kick the tail end out in abrupt turns. FUN if you want it, ANNOYING if you don’t.
The condition is called oversteer.
I swapped in a 3/4” rear bar from an ‘83 Imperial. I have the Mopar Performance XHD leaf spring set with 2 RH sides.
I'm good with a little oversteer. I do like this idea of 2 rights or 2l efts if I go the HD spring route. I wish there was more data on suspension tuning.
 

Darter6

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In 2007 we did this Cuda for the Hot Rod Power Tour.
Eaton Detroit Springs did the rear leaf springs. This had a 100 lbs increase over stock and a 2'' drop.
The car was built as a road cruiser for handling and a over drive 4 speed.
Eaton did leaf springs for several projects we did over the years. I am running the same 100 lbs and 2'' drop on my 63 Belevdere. They can do any rates you may want.

100_1169.JPG
 

Mr. Cranky

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Kern, I like the idea of passenger side XHD's on both sides. Shock and sway bar tuning is way beyond me.
Been a long time since doing an internet search but found a pretty good amount of info back when I did it....
 

davek

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ESPO ,bought them and was happy ,summit mopar hd springs are junk.
 

ckessel

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This one too if you can find it. The second edition with the red cover, the one in my avatar with my car on it, has the same info. Also if you can find the old circle track book, that would be helpful too.
Mopar Suspensions: Complete Guide for Building Mopar Suspensions for Street, Autocross, and Road Racing
Once I get my technology issue taken care of tomorrow, I can take a picture of the circle track book so you know which one. The later ones with the white covers don't have as much info as the older one.
 

66Satellite47

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I've heard from several folks that the newer Mopar springs are not durable. I know that the Mopar springs from the '70' & '80's were good. In the '90's the manufacturing changed location & again in the 2000's. I don't have direct experience with current parts. My SS springs are from early '90's. But they are not the correct spring for my car. So I have modified the leaf package to match what I used 40 years ago. I hope it works out with some tuning. My application is a mostly drag car. For a street cruiser I'd talk to the ESPO guys, or Detroit Spring, but they are really pricey.
 

hunt2elk

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I'm good with a little oversteer. I do like this idea of 2 rights or 2l efts if I go the HD spring route. I wish there was more data on suspension tuning.
I'm fairly certain that ESPO sells the factory style staggered XHD as well as a matched pair of XHD if you want them the same on both sides.
 

Rusty knuckles

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Dang those are some spendy books. I guess my search-fu isn't great. I've found lots of info of "I installed brand x this and brand y that and my car feels so much better." I guess what I've tried finding is similar to what you see in dyno articles with starting with a baseline, adding various components and showing their results. Here's a stock suspension lateral G capability and body roll angle (as examples) at whatever parameters. Then we installed this part from brand x and here's those numbers again. Then same part from brand y. Stuff like that.
 

davek

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Since when? Mine are from 2006 and the car hasn't sagged enough to notice.
bought a set for my 74 challenger and was not happy with them,they are yard art I couldnt give them away even though I tried. Made in Mexico ,they just didnt sit right for me. Leafs are not hard to install so I dont know what the problem was.
 

ckessel

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For sure the books are spendy, a good reason to watch for them at garage sales/shows/swaps/used book stores etc.
 

Mr. Cranky

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Me....I don't worry too much about springs. Even ones that are flat work well with 'big' sway bars. After all, the springs pretty much just hold the car up off the ground. If you like your car riding down the road like a 1 ton pickup, yeah, go for the heavy duty stuff. Our cars suffer from torsion baritis and that's a good thing because they are adjustable. Coils are not but so long as each rear leaf is about the same, the car will still act well with....big sway bars! Now if you want to go road racing....that's another story. And for even more handling.....splay your rear leafs a good inch or so outwards using offset rear hangers. Think about it. For a car that leans a little bit, it works.
 
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