Demon rear spring height

[Ironracer]

Thank you folks - appreciate all the info reported!! I have some measuring homework to do out in the garage.

I have to get back on this issue soon. I got derailed when the washing machine malfunctioned and provided me a flood that ran down into the basement. Been hauling wet junk out and running fans to dry the stuff that stays. Oh what fun....

Damn, that sucks...

 

[Ironracer]

Here is side view with SS springs. Might not be at all what you are looking for? But I will measure for you when I get home

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3rd Gen w/ a Lil overtired or stroke? Wicked Man, wish the 71 Demon i had didn't get away...

 

[Ironracer]

Factory XHD springs for A-bodies are 110 lb/in, not 140. SS springs start at 140 lb/in and go up to 160 lb/in.

Factory bumper height is listed here, which will give you the basic factory ride height (loaded). Full size version here The 1970 Hamtramck Registry - Chrysler Passenger Car Bumper Heights 1965 thru 1976 Slideshow
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Instructions for getting those heights are here The 1970 Hamtramck Registry - Chrysler Passenger Car Bumper Heights 1965 thru 1976 Slideshow
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Can I use the 12" # for my 74 Duster to set up my initial front end height? Then just check the sides? I've been sick *** heck for 6 weeks, covid to bronchitis, finally got some treatment. And moving a Lil. Wanna go finalize this mother so I can go for a ride

 

[72bluNblu]

Can I use the 12" # for my 74 Duster to set up my initial front end height? Then just check the sides? I've been sick *** heck for 6 weeks, covid to bronchitis, finally got some treatment. And moving a Lil. Wanna go finalize this mother so I can go for a ride

I don't see why not, I mean realistically you can set whatever number you want as long as you follow it up with checking/modifying the bump stops depending on what torsion bars you're running and setting the alignment (not to FSM specs for radials).

The better number to use for the front would be the suspension number though, the A-B spec'd in the FSM, since the suspension number is more important anyway. The factory didn't really give any corresponding number for the rear, which is where the bumper height thing comes in. But for the front suspension the FSM is pretty specific if you want to run stock heights...

 

[Ironracer]

I don't see why not, I mean realistically you can set whatever number you want as long as you follow it up with checking/modifying the bump stops depending on what torsion bars you're running and setting the alignment (not to FSM specs for radials).

The better number to use for the front would be the suspension number though, the A-B spec'd in the FSM, since the suspension number is more important anyway. The factory didn't really give any corresponding number for the rear, which is where the bumper height thing comes in. But for the front suspension the FSM is pretty specific if you want to run stock heights...

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Thanks Man! When I had the 66 Sat, the Old Pro (everybody's go to guy, since retired) pushed the front of the car up from where I had it. Ss in the rear, all factory parts, but poly bushings, front sway bar, w/ later k member. Car handed killer after he got done... SS in rear in the Duster too. Thinking I need to raise the front, but I'm darn near right on on the FSM # ... hmmmm... need to set height to lock (trq) the rear strut nut, then torque the LCA pin nut, drive way toe, and roll the block! Finding an alignment place is a joke. TAMPA BAY area..... you'd think someone would be worth a darn, they are all gone

 

[72bluNblu]

Thanks Man! When I had the 66 Sat, the Old Pro (everybody's go to guy, since retired) pushed the front of the car up from where I had it. Ss in the rear, all factory parts, but poly bushings, front sway bar, w/ later k member. Car handed killer after he got done... SS in rear in the Duster too. Thinking I need to raise the front, but I'm darn near right on on the FSM # ... hmmmm... need to set height to lock (trq) the rear strut nut, then torque the LCA pin nut, drive way toe, and roll the block! Finding an alignment place is a joke. TAMPA BAY area..... you'd think someone would be worth a darn, they are all gone

Yeah that’s exactly why I ended up buying my alignment stuff, I just do my own alignments on my Mopars. I’ll have them checked when I buy tires and stuff just to make sure I’m where I think I am. Most of those places are happy not to change anything with the amount of aftermarket parts I run.

As far as the height goes I wouldn’t go higher than factory. Literally the opposite happens compared to lowering, so where lowering ride height from the FSM specs generally improves suspension geometry for radial tires raising the ride height makes camber gain, roll center and other stuff worse.

 

[Ironracer]

Yeah that’s exactly why I ended up buying my alignment stuff, I just do my own alignments on my Mopars. I’ll have them checked when I buy tires and stuff just to make sure I’m where I think I am. Most of those places are happy not to change anything with the amount of aftermarket parts I run.

As far as the height goes I wouldn’t go higher than factory. Literally the opposite happens compared to lowering, so where lowering rods height from the FSM specs generally improves suspension geometry for radial tires raising the ride height makes camber gain, roll center and other stuff worse.

Damn...I didn't know that. On the 66, I had the largest height tires I could jam under the wheel wells ( after letting the frame hang the axle w/ a floor jack) and 205/70/14s front. So it may have needed it on that one... I'll double check the bottom of the adjustment lever to the slab and the bottom of the lower ball joint to the slab see where I'm at and if I do go up it probably won't be more than a quarter inch I think I'm within an eighth of an inch on each side already to the FSM specs

 

[72bluNblu]

Damn...I didn't know that. On the 66, I had the largest height tires I could jam under the wheel wells ( after letting the frame hang the axle w/ a floor jack) and 205/70/14s front. So it may have needed it on that one... I'll double check the bottom of the adjustment lever to the slab and the bottom of the lower ball joint to the slab see where I'm at and if I do go up it probably won't be more than a quarter inch I think I'm within an eighth of an inch on each side already to the FSM specs

Yeah the height of the tires is left out of the FSM specs, by subtracting those two measurements you're just dealing with the angle of the LCA. For comparison the stock tires, 6.95x14 or E70x14 are both ~25.7" tall. So if your front tires are taller than that you could have the same LCA angle as the FSM but if you measured at the bumper the ride height would be raised.

For radial tires the best suspension geometry really occurs when the A-B is fairly close to 0, the control arms are roughly parallel to the ground at that point so the camber gain is all negative, which is what you want for best handling. Obviously there's more to it than camber gain but the roll center improves with the car lowered at well. It's all a trade off of course, you just have to remember that the stock geometry (and therefore ride height) was based on what was best for bias ply's, not radials. It's just a nice coincidence that because the ride height is adjustable we can lower these cars and improve the suspension geometry for radial tires while still keeping the majority of the stock components and really the biggest issue that comes up is the lack of caster built into the UCA's.

 

[Ironracer]

Yeah the height of the tires is left out of the FSM specs, by subtracting those two measurements you're just dealing with the angle of the LCA. For comparison the stock tires, 6.95x14 or E70x14 are both ~25.7" tall. So if your front tires are taller than that you could have the same LCA angle as the FSM but if you measured at the bumper the ride height would be raised.

For radial tires the best suspension geometry really occurs when the A-B is fairly close to 0, the control arms are roughly parallel to the ground at that point so the camber gain is all negative, which is what you want for best handling. Obviously there's more to it than camber gain but the roll center improves with the car lowered at well. It's all a trade off of course, you just have to remember that the stock geometry (and therefore ride height) was based on what was best for bias ply's, not radials. It's just a nice coincidence that because the ride height is adjustable we can lower these cars and improve the suspension geometry for radial tires while still keeping the majority of the stock components and really the biggest issue that comes up is the lack of caster built into the UCA's.

Problem I have, as if I made the lca's flat the car would be sitting on the tires.. the top of the heaf of the adjustment bolts are already into the LCA by about 5/8"

 

[Demonx2]

Yeah the height of the tires is left out of the FSM specs, by subtracting those two measurements you're just dealing with the angle of the LCA. For comparison the stock tires, 6.95x14 or E70x14 are both ~25.7" tall. So if your front tires are taller than that you could have the same LCA angle as the FSM but if you measured at the bumper the ride height would be raised.

For radial tires the best suspension geometry really occurs when the A-B is fairly close to 0, the control arms are roughly parallel to the ground at that point so the camber gain is all negative, which is what you want for best handling. Obviously there's more to it than camber gain but the roll center improves with the car lowered at well. It's all a trade off of course, you just have to remember that the stock geometry (and therefore ride height) was based on what was best for bias ply's, not radials. It's just a nice coincidence that because the ride height is adjustable we can lower these cars and improve the suspension geometry for radial tires while still keeping the majority of the stock components and really the biggest issue that comes up is the lack of caster built into the UCA's.

I get the part about measurement A. But for the 71 Demon, what is measurement B? My 71 Dodge FSM says"...and from lowest point of steering knuckle arm, at the centerline, on same side (Measurement B)." Is this measurement to be taken back where the arm attaches to the tie rod? That would be the lowest part of the arm. But where along the length of the arm would you take the measurement?

My A dimension is right at 8.5". Just need to decide where to measure B. If I use B as the lowest part of the knuckle where the lower ball joint is, I get 8-1/8" which means my difference is only 3/8" which is well below the FSM value of 1-5/8". Just need to determine where B is really to be measured from. That would explain why I think my car sits too low!

 

[72bluNblu]

I get the part about measurement A. But for the 71 Demon, what is measurement B? My 71 Dodge FSM says"...and from lowest point of steering knuckle arm, at the centerline, on same side (Measurement B)." Is this measurement to be taken back where the arm attaches to the tie rod? That would be the lowest part of the arm. But where along the length of the arm would you take the measurement?

My A dimension is right at 8.5". Just need to decide where to measure B. If I use B as the lowest part of the knuckle where the lower ball joint is, I get 8-1/8" which means my difference is only 3/8" which is well below the FSM value of 1-5/8". Just need to determine where B is really to be measured from. That would explain why I think my car sits too low!
View attachment 1715973887

The "B" measurement should be directly under the centerline of the lower ball joint, to the lowest part of the ball joint housing basically. Like in this picture from the '73 Dodge chassis manual. Pretty sure the vertical columns are supposed to be rulers in the original graphic, I added the red arrows. Anyway, it shows "A" at the bottom of the adjusting blade and "B" at the bottom of the lower ball joint on the steering arm.

 

[Ironracer]

I get the part about measurement A. But for the 71 Demon, what is measurement B? My 71 Dodge FSM says"...and from lowest point of steering knuckle arm, at the centerline, on same side (Measurement B)." Is this measurement to be taken back where the arm attaches to the tie rod? That would be the lowest part of the arm. But where along the length of the arm would you take the measurement?

My A dimension is right at 8.5". Just need to decide where to measure B. If I use B as the lowest part of the knuckle where the lower ball joint is, I get 8-1/8" which means my difference is only 3/8" which is well below the FSM value of 1-5/8". Just need to determine where B is really to be measured from. That would explain why I think my car sits too low!
View attachment 1715973887

Definitely, a trick " question/ answer " lol. Has had me scratching the noggin fer a second...

 

[72bluNblu]

Definitely, the wording in the FSM is a little tricky. If you have the digital version of the FSM from MyMopar you can magnify that picture a whole bunch, larger than what I posted above. Makes it a lot easier to see what they were trying to show with their “rulers” in the graphic

Also, the measurement is finding the angle of the LCA. So you can use different reference points if you want, as long as they cancel each other out. The real measurement, which also determines the true length of the LCA, is center of pivot to center of pivot, ie, center of the torsion bar socket to the effective center of the lower ball joint. But that’s hard to measure, so, the factory used points that were easy to measure repeatedly.

 

[Ironracer]

Definitely, the wording in the FSM is a little tricky. If you have the digital version of the FSM from MyMopar you can magnify that picture a whole bunch, larger than what I posted above. Makes it a lot easier to see what they were trying to show with their “rulers” in the graphic

Also, the measurement is finding the angle of the LCA. So you can use different reference points if you want, as long as they cancel each other out. The real measurement, which also determines the true length of the LCA, is center of pivot to center of pivot, ie, center of the torsion bar socket to the effective center of the lower ball joint. But that’s hard to measure, so, the factory used points that were easy to measure repeatedly.

Quick question, does this look awkward to you? Not concerned about the "Look" LOL, just wondering if you thought everything loomed legit,, as fas as LCA angle,, obviously it's real hard to tell from a pic.... 295/50/15 rear w/ SS Springs, 215/60/15 fronts...

 

[Ironracer]

Camera was sideways, on front view of
horizontal Lca , just ran out to take those....

 

[Demonx2]

The "B" measurement should be directly under the centerline of the lower ball joint, to the lowest part of the ball joint housing basically. Like in this picture from the '73 Dodge chassis manual. Pretty sure the vertical columns are supposed to be rulers in the original graphic, I added the red arrows. Anyway, it shows "A" at the bottom of the adjusting blade and "B" at the bottom of the lower ball joint on the steering arm.

View attachment 1715973922

Thx for that instruction. That is the way I measured it so clearly my 8.5-8.125=0.375 (3/8") measurement is too small. Makes the front end lower than it should be. I'll get a pic later and post to show what the LCA looks like.
I can fix that for the front but need to do something corresponding in the rear to get the right look! Still undetermined on which springs to buy.

 

[33IMP]

I get the part about measurement A. But for the 71 Demon, what is measurement B? My 71 Dodge FSM says"...and from lowest point of steering knuckle arm, at the centerline, on same side (Measurement B)." Is this measurement to be taken back where the arm attaches to the tie rod? That would be the lowest part of the arm. But where along the length of the arm would you take the measurement?

My A dimension is right at 8.5". Just need to decide where to measure B. If I use B as the lowest part of the knuckle where the lower ball joint is, I get 8-1/8" which means my difference is only 3/8" which is well below the FSM value of 1-5/8". Just need to determine where B is really to be measured from. That would explain why I think my car sits too low!
View attachment 1715973887

In my opinion..... your green Demon sits perfect, as is.

 

[ir3333]

Stock they sat quite low and handled well.First thing most guys do is jack them up and if you go to the wheel tire section you'll find the height all over the place.
A good starting point would be to have the wheel opening a couple of inches above the top edge of the rim.

 

[Demonx2]

Stock they sat quite low and handled well.First thing most guys do is jack them up and if you go to the wheel tire section you'll find the height all over the place.
A good starting point would be to have the wheel opening a couple of inches above the top edge of the rim.

I was thinking in the front, the top of the tire about an inch lower than the fender opening when viewed from the side (i.e. 1" gap). Then set the back end accordingly to get "the look" of a bit of rake (you can tell my age!) without looking jacked up. Just a bit of a muscular look.

Now that I better understand the measurement method, I think I'll crank up the torsion bars to match the FSM and see what that looks like. (I have P205/ 70R14 front tires, 25.4" dia.) I'll get a before and after pic of the LCA to show what it looks like.

 

[Ironracer]

I was thinking in the front, the top of the tire about an inch lower than the fender opening when viewed from the side (i.e. 1" gap). Then set the back end accordingly to get "the look" of a bit of rake (you can tell my age!) without looking jacked up. Just a bit of a muscular look.

Now that I better understand the measurement method, I think I'll crank up the torsion bars to match the FSM and see what that looks like. (I have P205/ 70R14 front tires, 25.4" dia.) I'll get a before and after pic of the LCA to show what it looks like.

I ran those tires on the front of my 66 satellite with a 10-in wide wall tire tucked under the back but they were 15s in the rear car handled Excellent Man those 205 70 14 that's a damn good Tire they also look pretty even on a 14-in rim because the side walls got some meat

 

[Demonx2]

So I did some measuring and pictures last night. I found a lot of hysteresis in the suspension and had to roll the car back and forth a bit in addition to bouncing it up and down between adjustments.

The first thing I did was measure the P205/70R14 BFG Radial T/A"s. The internet says the are 25.4" dia but in reality, as measured, they are exactly 24" diameter (measured vertically).

Then I measured the existing top of tire to bottom of fender opening at the top of the tire. To me, this gap sets the "look" of the front end. As I built the car, it is at 3/4". Sitting my phone on the concrete floor standing up, here is what the LH LCA looks like, with A=8 5" and B=8.125" (B obviously does not change since it is just the dim of the lower part of the ball joint). These say then that my height = 3/8", well shy of the FSM of 1.625" (1-5/8").
LCA picture:

Then I adjusted the A dim to 9.5" (which sets the suspension ht to 1.375, still shy of the FSM value of 1.625"). That yielded a tire top to fender gap of 1.625 and frankly, looked excessive. So that tells me with this 24" tall tire, my suspension height will have to be less than the FSM specifies.

After a bunch of different settings, I settled on a tire to fender gap of 1-1/8" (suspension ht of 1", A = 9.125"). For reference, this sets the bottom of the fender opening (at the top of the tire) to be 25.125". Here is what the LCA looks like at this setting. It has a bit of a slope now:

Because the car is in the garage and blocked in by the avatar Demon, I couldn't get a good shot of the side look of the car. I'll have to wait until I can get the car out in the driveway to confirm this will be the right look.

Then, with the front where I want it, I'll put a jack under the rear of the body to see how much lift is needed to get the proper rake. Then I'll have to make a decision on what rear springs may give me this lift.

 

[testerli33]

I had the same "problems" with the rear height on my Duster. I had the original tired leaf springs with coil shocks in them, bought them already. I liked the height, but since I was redesigning the entire chassis at the front, I also wanted new springs and shock absorbers at the rear. I then decided on the Espo, 6 layers, floor height. Built in, frightening! Way too high:-( Then I bought the Hotchkis, installed them, they fit, exactly the height I wanted, but I had the problem that the shakers pointed too much towards the rear, and the shakers hit the chassis with the slightest bump. So I bought 1.5" lowering blocks and put the Espo back in. The height is absolutely fine, but I don't have much space between the shaker and the chassis here either, almost like the springs are too long. Spacers are not installed on the front hangers. The Espo should be a little tick softer, I'm not that much of a fan of lowering blocks. Does anyone know of an alternative spring? Otherwise I'll ask Espo if the 5 layers are also 1.5" lower

 

[72bluNblu]

I had the same "problems" with the rear height on my Duster. I had the original tired leaf springs with coil shocks in them, bought them already. I liked the height, but since I was redesigning the entire chassis at the front, I also wanted new springs and shock absorbers at the rear. I then decided on the Espo, 6 layers, floor height. Built in, frightening! Way too high:-( Then I bought the Hotchkis, installed them, they fit, exactly the height I wanted, but I had the problem that the shakers pointed too much towards the rear, and the shakers hit the chassis with the slightest bump. So I bought 1.5" lowering blocks and put the Espo back in. The height is absolutely fine, but I don't have much space between the shaker and the chassis here either, almost like the springs are too long. Spacers are not installed on the front hangers. The Espo should be a little tick softer, I'm not that much of a fan of lowering blocks. Does anyone know of an alternative spring? Otherwise I'll ask Espo if the 5 layers are also 1.5" lower

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That shackle position is fine, they're supposed to be pointed to the rear of the car like that. Even having the shackle vertical isn't considered ideal.

 

[testerli33]

I understand that the shakel position is OK, but the constant clicking is annoying :-( The problem wasn't with the original 5-ply springs, nor with the Espo, 6-ply, stock high. Then I installed the Hotchkis, and that's it notices that the shaker hits the chassis, so back to the Espo and lowering blocks installed, the problem remains, but I don't understand why. It worked without the lowering blocks, but the blocks don't change anything on the spring? I'm already thinking to reinstall the original leaf springs. Have 1.08 TB in front, Sway Bar Hellwig front and rear, Bilstein Shocks front and rear. Does anyone have any tips for me? Or have experience with other leaf springs which lower the car by about 1.5 inches without blocks ?

 

[Kiddart1]

I have mine as low as possible it's a Caltrac rear with a 3/4 spacer top of wheel well is at 27 inches to floor and the front is set at 26 1/2 inches to floor

I like mine sitting down in the weeds.