Leaf spring dimensions

[Steve Garner]

Yes, I know about all the other options, but I want to re-arch these XHD springs that are original to my 69 Superbee 383 car with the A36 packkage. The spring shop local to me does not have the specs to arch them to. They said they were looking for dimension E in my illustration. I can't find that dimension anywhere, however the front and rear measurements from the centre bolt to the eyes comes up. Does anyone know if those dimensions are measured at points A and B, which would give me the dimension needed for E. Thanks.

 

[33 IMP]

Sorry. I'm pretty sure the A and B dimensions are from the middle of the spring eye, to the middle of the rearend pin.
Maybe you could find a dealer (either local, or on the net) that has a new pair in stock, and ask for a measurement.

 

[Lefty71]

Why cant you jack up the car to the desired ride height and take the measurements??? I would think an experienced shop would know how far to "hyper" them based on the weight ratings of the spring.

 

[Steve Garner]

Why cant you jack up the car to the desired ride height and take the measurements??? I would think an experienced shop would know how far to "hyper" them based on the weight ratings of the spring.

Because the ride height has the springs in the loaded position, the arch is set with the springs relaxed and unloaded.

 

[j-c-c-62]

Yes, I know about all the other options, but I want to re-arch these XHD springs that are original to my 69 Superbee 383 car with the A36 packkage. The spring shop local to me does not have the specs to arch them to. They said they were looking for dimension E in my illustration. I can't find that dimension anywhere, however the front and rear measurements from the centre bolt to the eyes comes up. Does anyone know if those dimensions are measured at points A and B, which would give me the dimension needed for E. Thanks.View attachment 1590257

C, D, E unloaded as straight lines (chord), a, b & e are spring rate and load dependent.
Understand for most street/proper handling, a flat or very slightly arched spring is the goal, meaning you need to know your weight on the unsprung wheel/axle at rest to calculate your target "E" factoring in your spring rate.

 

[j-c-c-62]

Because the ride height has the springs in the loaded position, the arch is set with the springs relaxed and unloaded.

The simple weight of the axle and wheels will help over arch the leaf's a small amount.

 

[Frank Mopar]

I took my springs to a spring shop to have a main leaf added. Raised the car exactly 1”.

 

[Longknife]

Thats

I took my springs to a spring shop to have a main leaf added. Raised the car exactly 1”.

Thats exactly how I used to raise the rear on all my cars back in the day....

 

[j-c-c-62]

Thats


Thats exactly how I used to raise the rear on all my cars back in the day....

Long rear hangers did the same back in my day, and IMO, with a lot less drama.
Over arched leaf springs often promotes roll oversteer.

 

[Longknife]

Long rear hangers did the same back in my day, and IMO, with a lot less drama.
Over arched leaf springs often promotes roll oversteer.

I always thought those looked goofy. They didn't do the same thing either. Adding an extra leaf stiffened up the suspension a bit and reduced spring wrap when launching and raising an inch didn't cause over oversteer. There was no drama about it. It took about 30 minutes per side on a lift. The extended shackles hangers were a cheapo shade tree fix and added more chance of sway and handling issues, only installed by wannbe "mechanics" that didn't know any better.

 

[Frank Mopar]

He is my setup under a big of duress. Note rear of the spring is not clamped.

 

[Longknife]

He is my setup under a big of duress. Note rear of the spring is not clamped.
View attachment 1590659

HOOOK"N UP!!!!!

 

[j-c-c-62]

I always thought those looked goofy. And I suspect in that era you were in the minority They didn't do the same thing either. They accomplished the same thing Adding an extra leaf stiffened re-arching and adding a leaf are two different things up the suspension a bit and reduced spring wrap when launching and raising an inch didn't cause over oversteer. Raising 1" by re arching can cause oversteer I doubt you understand the kinematics here, do your homework There was no drama about it. This thread does not support that claim It took about 30 minutes per side on a lift. The extended shackles hangers were a cheapo shade tree fix and added more chance of sway and handling issues, only installed by wannbe "mechanics" that didn't know any better. Really?

https://s1.cdn.autoevolution.com/im...story-richard-pettys-1960-plymouth-fury_5.jpg

Granted that is a clone, but it was a very common set-up back in the day.

 

[70bigblockdodge]

If you measure the distance between the front spring hanger and the rear shackle in it's most forward position that the spring could still be installed, it would give you the maximum height of E dimension that would be practical. I would go 1-2" less than that because I have never had to do anything but swing the spring up into position and easily install the rear shackle, even on springs I have homemade.
Compare that measurement to the A,B measurement of your current removed spring and you should be able to get a close measurement to judge how much to re-arch. If your looking for exact spec.on rear ride height I doubt there ever was one specific number only a range.

 

[Steve Garner]

Thanks fellas. What I am trying to accomplish is getting as close to the exact factory ride height with the factory installed springs.

The car is a numbers matching car with full documentation going through a nut and bolt restoration. In my world it would seem a shame not to put the car back the way it was originally if you have all the original parts and supporting document. I don't think it's a particularly rare optioned car, but it is kind of neat. It's a 383 4 sp, buckets, console, ralleye dash and N96. It has the A36 axle package that gives it the Hemi/440 suspension (sway bar, half leafs on the left side) 26" rad, 7 blade clutch fan.

The objective is to have it appear just as it did as it rolled off the assembly line. The next owner can modify it like we did back in the day when we got them home.

 

[j-c-c-62]

Well, make sure the tires are properly inflated and there is no/little fuel in the tank.
If that was the known goal here, I would have remained silent.
Good luck.

 

[Longknife]

https://s1.cdn.autoevolution.com/im...story-richard-pettys-1960-plymouth-fury_5.jpg

Granted that is a clone, but it was a very common set-up back in the day.

And by the way I WAS a minority back in the day as I KNEW what I was talking about and I did things RIGHT, being a Chrysler factory trained mechanic and working at Chrysler garages from '69 to '79. Those extended shackles were widely used because they were cheap and easy.

 

[RemCharger]

I always thought those looked goofy. They didn't do the same thing either. Adding an extra leaf stiffened up the suspension a bit and reduced spring wrap when launching and raising an inch didn't cause over oversteer. There was no drama about it. It took about 30 minutes per side on a lift. The extended shackles hangers were a cheapo shade tree fix and added more chance of sway and handling issues, only installed by wannbe "mechanics" that didn't know any better.

Spot on.

 

[j-c-c-62]

And by the way I WAS a minority back in the day as I KNEW what I was talking about and I did things RIGHT, being a Chrysler factory trained mechanic and working at Chrysler garages from '69 to '79. Those extended shackles were widely used because they were cheap and easy.

Who obviously still hasn't as suggested done his homework.


Enough of the games.

From #9 here:
"Over arched leaf springs often promotes roll oversteer."

When an arched spring compresses from additional load on the outside wheel during a turn, the axle moves rearward in its upward arc, when the inside spring loses load in the same turn, it extends and it's arc moves that side of the axle forward.
Voila, we have roll oversteer.
That must have been left out of Chrysler mechanics training in the seventies, I guess.

 

[Steve Garner]

Who obviously still hasn't as suggested done his homework.


Enough of the games.

From #9 here:
"Over arched leaf springs often promotes roll oversteer."

When an arched spring compresses from additional load on the outside wheel during a turn, the axle moves rearward in its upward arc, when the inside spring loses load in the same turn, it extends and it's arc moves that side of the axle forward.
Voila, we have roll oversteer.
That must have been left out of Chrysler mechanics training in the seventies, I guess.

I've held a Journeyman's Cert since 1978 and had never heard that either. The explanation fails to take into account the straightening of the spring as it deflects. So while moving up in it's arc pivoting on the front eye brings the axle forward, straightening of the spring arc increases the distance from eye to centre bolt thus moving it rearward.