My '72 Dart project had minitubs and a pair of unknown springs when I bought the shell. Today I put the car on the ground and drove it a short distance. But it looks way low in the rear (raked?) and not even symmetrically. The shocks only have about 1.5 and 2.5" of rod exposed.

How much arch should there be in a stock spring? Or is this pair just not heavy enough for the car even though it no longer has a back seat?

Those look like a H.D. spring set(not stock OEM light duty 5 leaf springs) with 6 leafs on each side, is there a part number stamped into the bottom leaf facing down?
What does the rear shackle angle look like at rest, straight down angled to the front of the leaf spring or angled back towards the rear bumper?

Springs could be tired. I count 6 leaves in each side. The left side is almost flat. One thing you could check is with the car on jack stands supporting the frame, on a level floor, measure the distance between the front spring eye bolt holes to the ground. Should be the same. And if there are multiple holes in the box, insure both sides mounted in the same relative hole. Insure the rear spring hangers through bolt hole positions are the same as well. If everything measures up then it's time for some springs. Or throw another leaf in each side. You might also check for part numbers on the springs and post them here. MP SS springs have a left and right side orientation. Usually stiffer on the right spring than the left. 6 banger and 318/340 stock springs usually have the same pn on both sides, in my experience.

I will check tomorrow for part numbers. The rear shackles are angled backwards about 2" (spring eye behind the frame end of the shackle). The spring eye looks close to the frame rail. Is that how they're supposed to look?

You want the bottom of the rear shackles to be rearward from plumb (vertical) otherwise if it is in front, the spring will raise the car as it compresses in that arc over center.

ok, then the shackles are angled correctly. I suspect these old springs are just tired.

The battery is in the right rear of the trunk, and the fuel cell in the center. Stock heavy bumper. So back to my original question, shouldn't there be an arch visible in the spring? As pointed out, they look nearly flat just sitting there.

Something else occurs to me - if I don't have the ride height on the torsion bars set symmetrically, will that force the rear to sit differently too? Haven't checked for that yet.

The more heavy duty the springs are, the less arch they tend to have. If there is a negative arch to the rear spring, you may have some broken leafs in the spring pack. The leafs tend to break at the center bolt, which would be mid way between the the sides of the U bolts. One or two broken leafs in a spring will cause a pretty bad sag. If you bounce the back end of the car, does it return to the same level?

The reduced shock travel probably means someone put a set of shocks off a B body on your A body car, or something else is not right. I've seen broken springs with more shock travel the 1"-1 1/2". Generally, there should be a bit more then 4" of shock travel before the shock would bottom out.

Incorrect torsion bar adjustment will have an effect on the rear height, side to side. If the left torsion bar is significantly lower then the right torsion bar, the left rear will be lower then the right rear. Gene

I'll look them over closely for broken leaves. No negative arch, just awfully flat looking... yes, bouncing does return.

I bought the rear shocks a while back, through the classified ads here on Moparts (Calvert Rancho 9-way adjustables). They were supposed to be A-body, and they did bolt up and have enough extension to let the rear hang with the frame on jack stands. Didn't occur to me to check compression! Looks like I should check their part numbers, too.

Mopar springs, when installed and the car is on the ground, may appear to be nearly flat. In most cases, the installed arch is no more than 2". This is by design for improved handling purposes. Exceptions to this may be station wagons, trucks, and of course, drag race competition springs. Mopar oval track competition springs may actually have reverse arch to them.

From what I can see in your pictures, they appear a bit flatter than original, but not radically so. It could even be camera angle. Your overall ride height in relation to the wheel appears okay. The extra leafs mean they also have a higher rate so even though they may sit a bit lower, they have more resistance against bottoming. Judging from the length of your u-bolts, and the leaf count, these are not original.

If you have competition shocks, they are designed for spring with more arch. You may not be using the best range of their motion, but may still be adequate.

Unless you are bottoming out or bouncing around, there doesn't appear to be any major issues going on here. If either of these are the concern, they can be addressed with a change in either the springs(bottoming) or the shocks(bouncing). If you are simply unhappy with the ride height, then that can be changed with a spring with more arch(camber).

You may be able to flip the front spring mounts to gain some hieght.

Thanks for the suggestions everyone. The previous owner did (or had done) mini-tubs and relocated the front mounts into the frame rails. I need to take a close look and see if anything can be moved.

The bigger problem is that there's 1.5" difference in the ride height side-to-side... I suspect a cracked leaf, or just plain worn out.

If your front mount is i the frame rail, the flip trick above is not an option. Depending on their accuracy in doing the spring relocation, there may or may not be issues with the front hanger location. Some people put two mounting holes in the relocation kit, some only put one. I'd certainly recommend checking these mounting locations for the front spring eye and ensuring they are equal and/or try changing their mounting hole if you have a choice of two.

If your leaf mounts are indeed symetrical, you can offset the rear height difference by adjusting the front torsion bar bolts. The corner opposite of you high leaf can raise up a turn or two. This will tend to bring down the high rear corner and level out the view from the back.

OK, but what will that do to the front heights? Offset them too, right?

I am not so sure the amount of arch is as crucial is as how the springs move when in use. Meaning, maybe stating the obvious, any compression movement that that moves the rear axle forward on the outside wheel in a turn, reduces oversteer characteristics, and any movement that moves axle rearward under compression on the outside wheel of a turn, promotes oversteer, on leaf spring cars,that move the axle thru a small arc under different loads. The inside wheel is the opposite, but plays less effect since it carries less load/grip when cornering. This should be easy to visualize.

This is why production springs have very little arch, for toe control.

Drag race springs (without traction aids) generally want stiffer front segments, a higher front eye, and bias for launch control.

Today I measured the front ride heights... and found to my surprise that the left was much lower than the right! At least an inch. I knew it would have some effect, but I'm surprised at how much difference it made to the rear heights

To fix it I had to disassemble the adjusting bolt & block since the threads were galled and would barely turn, but with the help of my Lang (USA made) rethreading set, it's adjustable again. The damaged bolt threads are past the area of adjustment that I need anyway... something else I probably knew about and forgot to fix several years ago.

Now, with the fronts equal, the rear is now just about equal too. But they are both too low (the bead edge of the rim lines up with the rear quarter lip. I want it a couple of inches higher anyway, especially since the front can't be down on the deck with my 8 qt pan, Lakewood and underchassis headers/dual 3" with X-pipe exhaust.
Looks like it's time to order a pair of springs!

Edit: there is less than 1.5" compression travel on the Calvert/Rancho shocks and they bottom out with a good push on the trunk. Definitely designed for a higher ride height...

Now you see the impact of front ride height on rear height. Diagonal weight tranfer acts much like a see-saw. If one corner is too high, adjusting the opposing corner can change it.

With a min-tub and inboard springs, its a distinct possibility a previous owner had competition springs on it, which have considerably more arch than stock and would be consistent with the longer travel shocks.

If you want a taller overall ride height, there are only two ways to get there, change the mounting location of the springs, or change the arch of the springs. Changing the arch in the springs can be done by have the pack dis-assembled and re-arched or swapping in a higher arch set. Higher arch sets can be custom made with whatever arch and rate desired, from a place like Springs and Things, or you can go the simple bolt in Super Stock route.

If it were me, I would upgrade to Caltracs and his springs. You have not posted a side view of the car so it is hard to get a good idea of ride height.

I'm thinking of buying a set of Caltrac bars (especially since I already have the shocks) They work with stock springs too, don't they?

You have to fix your springs already so why not get the right ones to start? The bars will work with stock springs but not as well as the monos. I know because I have done it. Get the whole package from Calvert.

The Dart will mostly see street time and the mono-leafs show quite high spring rates. We have crappy roads here in rural MO, too.

The monoleafs are $429/pr plus shipping, too. Budget is a factor here... one reason it's taken me 21 years to go from a bare block to a running car I can start to debug

I may experiment with clamping the front segments - have you tried that and how'd it work out?

Clamping the spring ends on the front segment will help with traction, but qon't do a thing for ride height, or short shock travel.

You either need to relocate the ends of the spring height lower on the body, put more arch in the springs, or replace the springs if you want to change the ride height. I suppose you could go old school and add longer rear shackles, but I wouldn't go there. Gene

Right, I didn't mean to imply that clamping would change the ride height. I just brought that up since I'd mentioned Caltracs. I've read too many bad things about longer shackles to want to go there either

These springs are ancient. I'm going to replace them. Then we'll see

Replacement leaf spring sets from Springs and Things in your choice of arch will run around $220-250 a pair. SS competition springs from Mancini will be around $300 a pair. Shipping is on top of those prices.

If budget is a concern, you could remove and dis-assemble your current packs, purchase a pair 2" add a leafs for around $50, and re-assemble your springs with the lift spring, adjusting the leaf count for your ride preference.

If you don't have one already, pick up the Mopar Chassis book and learn how to tune the leafs you have now before you run down the Cal-tracs path on a predominately street use car.

I've read that add-a-leafs will only band-aid things for a while?

I've still got my Direct Connection Chassis and Engine books that I bought in '83 and have read them

Caltracs don't sound like the best option for the street, so far.

Exactly.
Stock springs were designed to be flat under average intended use. That's why there were so many different spring packs.

reposting from another thread:
Increasing the rear arch can improve launch on the drag strip if properly combined with sticky tires. It is also used sometimes by circle track cars in combination with other changes to improve coming off the corners.
On a production car, arch can have negative handling effects.
Flat is basicly correct. This is how Chrysler designed 'em. Chrysler explains it in the in this booklet about handling.

Trying to find the original rear ride height is difficult.
The only rear height info I've seen from the factory is at Hamtramck Historical.
http://www.hamtramck-historical.com/PassengerCarBumperHeights-01.shtml Note that on page two that these are for fully loaded (5 passengers, full fuel) but does not say what options. Also the bumpers are somewhat adjustable and the body has some slop. So these are visual body related, not so much suspension setup info.


If you will be taking it to the track, then the arch may be helpful.

Adding helper springs is only good for specific loaded situations. Otherwise its stiffening the rear roll rate and can lead to oversteer when your not going to appreciate it.

Or maybe to be more precise, flat and approaching level.

The shock absorber has less travel when standing more upright. The original position has a very steep angle to it. You not only lost compression travel but the same shock is now stronger in that position.

Though you may hear others say don't do that.... you can very easily re- arch your spring sets. I personally have done many of them. in fact , I put the whole spring pack in a press at one time ! measure your free arch . with the spring lying on its side on the ground . measure from the centering pin [ that bolts the set together] up to a center line through the spring eyes. put the springs in the press -- the front segment should be bent at about 4 and 6 " back from the front eye. a good 20 ton press will put 1/2 " more arch in them. try to put pressure in 2 places 2" apart . be careful! it takes effort. the spring will bend a long way and still come back so bend some and re-measure it . the springs may settle back some ...the 1/2 " will get you about 1 " in rear ride height gain. you will be happy with it. cost 0.00 $$$ or , you can put in longer shackles at the rear.....

the toe is fixed in a solid rear axel. you have to bend the tubes to change it . rear steer is what you are talking about . as the leafs compress, they move the rear end back... if the arch is different in the pair of springs, the long side will move further and will steer .....

It rear steers because “toe” has changed through suspension travel - toe relative to the centerline of the car.

On a hard turn one rear tire toes in the other out - relative to the centerline of the car.

However that is not true with deep arched springs if both wheels stay both on same side of axle centiliter in a hard turn, There is still a steering factor, but its not because wheels are moving opposite directions. This exception would certainly not be the norm.

ek3's has a valid point about using the term 'toe'. We understand what was meant but it could mislead someone. Rear steer effect is more correct description. Toe is better reserved for the relation of the wheels to each other.

AFter looking at it I agree some people would get confused by using the reference to toe.

Rear steer or the correct term “thrust angle” is better.

I am NOT picking on anyone.... toe is when the distance between a pair of tires is not the same . toe in, is less, toe out is more... when cornering in a left hand turn , the right rear [ body ] will roll over and this causes the right rear spring to flatten out making the right rear tire to move back. at the same time , the left rear [body ] is coming up, causing the left rear tire to come forward. thus the rear end has turned to the right . just like a pair of wheels on a creeper do when it is turning . the toe has not changed at all or at any time . if you place toe plates on the rear and measure , what you have is what you have .you can turn the rear but , both tires are moving together . the front spring segment travels through an up and down arc as well and as the spring is flattened out , it gets longer so that side goes backwards. the opposite happens to the other side ! just trying to explain- I know you meant the same thing.

I just wanted to give the op an option of arching his current spring packs and not spending any cash.....

Thanks, I appreciate the extra detail. But I only have a 12 ton press and anyway I'd need more than 1/2" arch, at least on one of them.

I think these 46 year old springs have had their day and it's time to recycle them into coat hangers New ones will be here tomorro.

I don'think your springs are original, so I wouldn't necessarily put them out to pasture yet, but if they do not provide the ride height and drag performance you want, then there is no point in keeping them. Their low arch and higher than stock rate does make them desirable to handling applications. You might be able to resell them to an interested party.

What springs did you order, if I may ask?

These: https://www.generalspringkc.com/product_p/33-909.htm

It says "2-1/2 inch lift" so I was a bit wary - but they finally came today and I just finished putting them on. The car looks just right. I don't know if the spring relocation has the front eye at the same height as original - it may have been lowered by whoever did the work.

The shackles are pointing towards the rear, but at a less acute angle. With the old springs, the rear eye was just about hitting the frame. I may try lowering the front just a hair. It's a little high right now but Milodon oil pans are expensive to replace!

Now for alignment, what should I do about the front ride height? I weigh anywhere from 260 to 295 lb depending on the season so should that much weight be in the driver's seat? Will only occasionally have a passenger.

What season should I drop in for the plentiful fixings?

I might be able to help you balance the car out riding shotgun.

Yes but do talk to your alignment guy, some systems compensate for drivers weight (avg wt I would assume). Might not be critical but asking is free. I dont have the last word on this but I would want a "neutral" alignment with my weight in barbells setting on the pass side & instruct him to pull em over to the drivers side when he drives it on the rack before he exits the vehicle. My 65 dart just floated down the road when done (with max caster)

When you say "neutral" it sounds like you mean: with my weight in the driver's seat while it's on the rack, right?

Three bags of ready-mix (240#) or Portland cement (282#) should be close enough, and easy to handle compared to iron weights

I've got tubular A-arms so should have plenty of caster available. Manual steering, currently stock 24:1 but if PST ever makes a 20:1 box I'll buy one. Figure around +4 degrees is OK (I'm not too worried about increased steering effort).