Steve: The 1957 Ford shop manual gives the 57 Tbird rear springs (5 leaf) a deflection rate of 100/110 Lbs per inch. This seems soft but it will give you a starting point. Pete   Wanted to add; Front coil springs are 290 lbs/inch with a free height of 14.99 inch.

I looked up Eaton the other day - and they sure are proud of their springs - whew! The material they claim to use is pretty much universal - so rocket science isn't what they are selling. One of the local HAMB guys has suggested Arizona Spring as a place to "shop" here in Tucson, so I may go over there next week. Using a local source could be the best idea anyway.

Many of the web sources I've found all use the same part numbering scheme for the bird springs - so I'm thinking there is a "root source" vendor somewhere. Might take a while to find them....but it could net some better pricing (and more specific information). No one seems to know what the load ratings of the various varieties are.

I did grovel under the car yesterday, long enough to find a "fifth" leaf on my outfit - but the tiny fifth leaf doesn't look to be a major load carrying or stiffening member.

 
 Steve Metzger       Tucson, Arizona

Steve, my 55 originally had 4 leaves and I added one. I will say this it does firm the ride and turn control. I notice it much more now than when I did it. I was about 18 yrs old then!



I've always wanted to remove it and try a coilover setup instead just out of curiousity.



I also plan to fabricate a panhard bar and traction bar setup in the soon to be.



Back when, I simply disassembled the spring leaves and had them make an extra full length leaf at or local front end shop. It was an everyday thing. That shop is still in business today and will still make them up. Let me know if you want me to investigate that option.

       A  L  A  N   F  R  A  K  E  S   ~  Tulsa, OK    

    Check with Eaton Detroit Spring,Inc.--(313)963-3839 or www.eatonsprings.com as Frank suggested.They have over 166,000 stock applications and 24,000-plus OE blueprints to produce almost any manufacturer's specs and an in-house design staff that can create custom applications for any vehicle (copied from their brochure).  KID

Steve,

        You might check with Eaton in Detroit also. For reference if nothing else.

Frank/Rebop

Bristol, In ( by Elkhart) 

Thanks John - mine has four leaves and the frame re-inforcement straps - its an "'early" '56 I believe. I found a couple of places on the web:

www.thesuspensionking.com

www.generalspringkc.com

These two both offer 5 leaf "heavy duty" replacements, I'm thinking maybe I'll give them a call.

 
 Steve Metzger       Tucson, Arizona

Steve:

I believe the '55 Birds originally has 4 leaf springs.  The early '56s had 4 plus stiffener bars on the bottoms of the box frame, about 3/8" x 2", full length of the side rails.  This was to offset the cantilever effect of the continental spare tire.  Later '56s had 5 leaf springs and heavier frames.  57's  continued in the '56 configuration.  Since the 4 leaf setups sagged pretty quickly, I figure the 5 leaf springs became the replacement for all three years.  My 2 cents.

John in Selma, IN

John - "The Hoosier Hurricane"

I recently saw a comment (on another site) about the 1957 T-birds having a different (stiffer) rear leaf spring than the 55-56 models. Seems to me that whenever I've seen replacements for sale - the same part was listed for all three applications. Does anyone have direct experience with this?

I''ve been thinking I'd like to put some stiffer rear springs on my outfit - not outrageously so - but to control the axle a little better without auxillary traction bars. My first idea - and I may still go down this road - was to have a custom spring leaf made and then add it to what's on there now.

 
 Steve Metzger       Tucson, Arizona