I recently installed a pair of Mopar performance leaf springs in my 69 Dart, Part number P4510268-9. They are sold as XHD original equipment spring. I got a good deal on them, but otherwise I wished I had never bought them.
As with SS springs, the passenger's side has a higher spring rate than the drivers side which has the car sitting about 1 inch higher in the rear on the passenger's side.
At the same time I was replacing the springs, I also had removed the driver's side torsion bar in order to pull the headers that were on the car. When I reinstalled the driver's side T-bar. I found that the driver's side was sitting lower now in the front with it's adjusting bolt set to the same position as the passenger's side.
Is this being caused but the higher leaf spring rate on the passenger's?

The pass rear stiffer rate could be pushing down the front.

As far as the bias design on an handling car, that gets debated. I have bias springs and kinda like it to balance traction getting coming of the slower corners.

The ideal approach is to scale each corner and adjust T bars to balance "as raced". If that leaves it a little unbalanced standing still that may not matter if it acts right rolling and especially under high power.

As far as my question. I found a old post where someone said that their SS spring were causing the front passenger's side to be lower than the driver's side. The opposite situation that I have.
A friend told me that I might have not had the control arm down enough when I reinstalled the T-bar. He is indicating that is why I have to crank the adjusting bolt so much more on the driver's side.
I really don't think that is the case.

I don't think that's the case either. If I'm recalling correctly my front-end rebuild a few years ago.. yes, you drop the LCA down to withdraw the T-bar.. but inserting the T-bar into the LCA socket differently on one side from the other would have a HUGE effect ---> that's going to twist one T-bar 30 degrees more than the other side.. it would not be an inch.

- Art

I haven't seen the XHD springs doing what the SS springs do (RR higher than LR). The normal deal with SS springs is to crank the LF T-bar up to level the car side/side, though some guys claim that messes up the SS spring setup's ability to control torque steer. Other guys run the same # on both rear and claim it works fine & avoids the leveling deal. Bottom line seems to be that every car's different. I've beaten the heck out of the Archive button to no avail, haha.
I'm fooling with that right now on a car to get it to quit hooking right; the street tires on it may be a contributing factor - this thing just BLOWS the tires off - but I'm not sold on that conclusion yet. This week's thinking is to clamp the front of the RR spring to see if that pre-loads it.

I chose after reading many threads about this subject, Mancini HD springs. Not SS springs. I went with Mancini springs because of the feedback. They are a level spring . No bias. A lot of people did not like the raised stance to once side, or how high the SS springs jacked the car up. I am happy with the HD springs. Nice ride height and level. I have them in my 69 Dart. Def thinking you have a torsion adjustment issue. The bars could of been adjusted to old worn rear leaf springs and would of needed adjustment anyways.

Here is a pic of the springs. When the I heard that a friend was selling them, I first asked if they were SS springs as I did not want to end up with a back end that was not level side to side. He said that they were XHD factory replacement springs.
After looking them over I noticed that there was a left and right side part number.
Both spring have a total of 5 leaves at the center bolt, but the lengths of the leaves and location of the spring clamps vary between the two.

I had the same problem on my 69 coronet. XHD springs DCC-4452982 and 3.This was on a completely new build,so i didnt notice it because i had to level it from the start.2 years later i was putting a rear sway bar on it and had a hard time hooking it up ,about 1" higher on the right side(jack stands under axle)I didnt like it .so i replaced them with mono leafs.I like it much better now.O yeah left side was 5 leaves right 5 plus 2 half leaves.

What does it matter if one torsion bar has more tension on it then the other? You have to level the car right? If the right rear has preload or more tension then the left, of course it will affect the diagonal corner.

Will biased leaf springs affect the front T-bar adjustment? Yes. Typical means is to adjust the opposing t-bar up a bit to offset the imbalance. Whether or not that impacts a drag launch depends and can vary from car to car and driver to driver.

Typically XHD springs don't do this but SS sets certainly do. I'd also verify both shackles are pointed rearward. Sometimes they can flip forward during install and if you miss this, then one side will sit higher.


Since you took the driver's side bar out and re-installed and now it sits low relative to the adjusting bolt, I'd lean towards not exactly duplicating its re-install, IE a hex off. The lower control arm should be as far down as possible to align the bar install. It is possible to raise it up to the next aligning hex and install without enough load on the bar. You would only want to do this if you are running a t-bar in the 1.2X size. Anything smaller will require adding more and mroe adjusting tension as t-bar diameter goes down to restore original ride height.

Thanks, I have been figuring that the right rear spring was the cause of the left front being a little down and needing more t-bar adjustment to level the front end. Both shackles are angled back even and correctly.
What puzzled me was that I had read where a higher spring rate on the right side would cause the right front to be down some. The opposite of my situation.
If these springs weren't so expensive ($212 for one spring). I would go out and by another right side one and then install it on the left side to level the rear.

In my experience, whether it is cornering or straight accelleration, the majority of weight tends to transfer diagonally and the opposing spring is what is usually impacted. Weight does transfer a percentage fore/aft and sideways, but the biggest impact is on the opposing corner.

Think of it like a four legged table. If one leg is a hair long, what happens?

yeah, it's diagonal as far as ride height front to rear.

I put SS springs on my coronet and the left rear was higher, i turned in the right front torsion bar adjuster a few turns to level everything out. the right front came up and the left rear went down.

Weight scales would sure come in handy about now.

Every 1962 and up Mopar A,B and E body car, stock or set up for drag racing, I have weighed all four corners on had more weight on the front end than the rear and the L/F had the most weight, a little less weight on the R/F, the L/R was heavier than the R/R without the driver
Once you put the driver in it does affect the weights on the corners also just like moving the battery to the right rear corner of the trunk
My old pump gas Duster with the motor moved back one inch and the rear end moved forward one inch with ladder bars and coil overs had 50.5 % weight on the front end with me in the car and full of fuel in the stock gas tank with two group 27 batteries in the R/R corner of the trunk and 49.5 % on the rear
That car sat level without me in it and had pretty near even front rise under WOT with stock six cylinder torsion bars adjusted to get the front ride height level in the middle of the stock FSM ride height specs.

Every car I put SS springs on always sits a bit unlevel. And I always have to adjust the torsion bars some to get them to sit ok. Some say don't change the torsion bars but I sure as heck wont drive a Mopar down the road sitting 4 or 5 inches unlevel. Actually my 63 sat more unlevel then most I do as it was a good 4 or more inches off and I adjusted my torsion bars to get it level. The car handles normal and works fine at the track. About the only thing they may contribute to is my 63 pulls the left front up more then the right front when I launch at the track but the car goes as straight as an arrow. You can have them sit a little unlevel of maybe and inch or 2 but I wont drive my Mopar sitting any more unlevel then that. And other then changing the leaf springs again if it sits off after new springs went on adjusting the torsion bars is the only way to level the car out some. I have adjusted many torsion bars on cars that got SS springs and they have all drove fine and worked fine at the track. Ron

What is ideal for drag racing may not suit the set up for everyone else.

One popular misconception is a strong spring is a taller spring. In the case of SS springs it is. The right rear is not only stronger (more leafs) but it also has more arch (height).

If preloading does not suit you. Dearch the passenger side or arch the driver's side an inch or two.

or get two right/left side springs instead of the "set".