1956 are rear springs worn out?

woodeye

woodeye

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Gold Member
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Mar 12, 2021
Thunderbird Year
1956
I'm getting ready to start working on my 56. last year it looked like the car might be hanging low in the rear. Is there a standard height the car should sit off the ground measured at the rockers or the top of wheel arch on the fenders.
Is there a kit that would include the spring, shackles, bolts and bushing.
Also I've read that guys recommend up grading to larger front and rear sway bars. How big were OEMs to know what I have now.
 

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woodeye said:
I'm getting ready to start working on my 56. last year it looked like the car might be hanging low in the rear. Is there a standard height the car should sit off the ground measured at the rockers or the top of wheel arch on the fenders.
Is there a kit that would include the spring, shackles, bolts and bushing.
Also I've read that guys recommend up grading to larger front and rear sway bars. How big were OEMs to know what I have now.
Click to expand...
I am not sure about the "factory standard" of height the frame should be from the ground but if it is drooping, they are probably shot. My 55 has a set of shackles to raise the rear but I know the springs are fatigued. You can buy replacements for about 300 a side or go to a local spring shop and have them re-arced. I suggest the former. Fresh steel is best. Once the steel fibers are yielded, they don't last long when re-yeilded. The problem is this: Getting the bolts out. The forward bolts are much more difficult and can require equipment that you don't likely own. It is worth the money to have them either remade (local shops do this routinely) or purchased new from one of the many specialty suppliers and taken to a shop for R&R. And never let them toss the old ones. Hang onto anything removed.
 
24" from center of taillight to the ground.
 
For 55 and 56 (57 different)

Factory Heights, measured from the center of the headlight to the ground (front) and the center of the taillights to the ground (rear)

Front 28.6
rear 22.76

With two people in the car
 
What's the source for these numbers?
 
Last edited by a moderator:
The best method is to deteremine the "free arch" with the springs out of the car; if there is some stat that others may have on what that should be. It is a measurement from the the midpoint of a horzontal line between the "eyes" of the spring to its midpoint. at the peak of the arch.

Repro springs are prob best, many re-arching shops don't do it correctly as its a big deal - the springs have to be re-shaped and then "annealed" properly. Eaton springs is one of the few that still do it properly. The attachment is about vintage Corvette springs but it applies to nearly all vintage cars.

In my expereience these folks make the best repros but they aren't cheap:
www.eatondetroitspring.com

Find Leaf & Coil Springs For Your Vehicle (Also Shocks, Installation Kits, & More) - EATON Detroit Spring

Select the Year, Make, Model, Body Style, and Engine Size of your ride below. Help Ordering Online If you cannot find your springs in the parts lookup below, call us during office hours at 1 (313) 963-3839. Alternatively, fill out this form completely to request a quote from our sales team.
www.eatondetroitspring.com www.eatondetroitspring.com
 

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After 67+ years probably 75% of the T-Birds are not level due to worn springs. For 1955 and 1956, the center of the taillight should be 22.76 inches from the ground, and the center of the headlight should be 28.67 inches from the ground. For 1957, the center of the taillight should be 23.30 inches from the ground, and the center of the headlight should be 28.07 inches from the ground.

doug7740
1955 Thunderbird Blue

Untitled.jpg
 
4VE said:
I am not sure about the "factory standard" of height the frame should be from the ground but if it is drooping, they are probably shot. My 55 has a set of shackles to raise the rear but I know the springs are fatigued. You can buy replacements for about 300 a side or go to a local spring shop and have them re-arced. I suggest the former. Fresh steel is best. Once the steel fibers are yielded, they don't last long when re-yeilded. The problem is this: Getting the bolts out. The forward bolts are much more difficult and can require equipment that you don't likely own. It is worth the money to have them either remade (local shops do this routinely) or purchased new from one of the many specialty suppliers and taken to a shop for R&R. And never let them toss the old ones. Hang onto anything removed.
Click to expand...
Your dimension from the tail light to the ground is meaningless. That is a static dimension, the spring is a dynamic device that is designed to flex under a specific range of loads. The "push back" of the spring is an engineering calculation. The spring guys know their materials and loads. The spec you seek concerns the dynamics of the material, dimension of the arc, number of leaves, dimensions of the leaves, etc. I suggest you acquire NEW springs designed for a 1955 TBird from a reputable vendor. And yes, the car did not come with a rear stabilizer bar. Get one, you won't regret it.
 
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