Suspension Question - GT coils vs 620 lb coils - Page 2 - Vintage Mustang Forums

Thread Tools
post #16 of 18 (permalink) Old 03-20-2017, 07:25 PM
Join Date: Apr 2013
Posts: 33
a STOCK 1965-66 K-code/GT Coil spring is 600 pound increased rate--does not lower car 1 inch
jhayes4554 is offline  
Sponsored Links
post #17 of 18 (permalink) Old 03-20-2017, 09:31 PM
Senior Member
GT289's Avatar
Join Date: Sep 2006
Location: SoCal
Posts: 6,462
Originally Posted by jhayes4554 View Post
a STOCK 1965-66 K-code/GT Coil spring is 600 pound increased rate--does not lower car 1 inch
That would be a C5ZZ-5310-A spring. (1491 load rate, 0.60" wire diameter, 8 coils total in free length and 4.45" is the mean diameter)
From the math.......11,250,000 x (.6 x .6 x .6 x .6) / 7 x 7 active turns x (4.45 x 4.45 x 4.45) = 337 Lbs/in

The GT/Special Handling spring was not even close to a 600 pound spring.
Our .67 wire diameter spring for our kits was marketed at 540 pound and by the equation above is right around over 500.

Shelby used the stock springs; in conjunction with the Arning drop, that's how the cars ended up about 1/2" lower.

ex-Global West GM

As the drill sergeant said, "I taught you everything you know. I didn't teach you everything I know."

"Human beings, who are almost unique in having the ability to learn from the experience of others, are also remarkable for their apparent disinclination to do so."
- Douglas Adams
GT289 is offline  
post #18 of 18 (permalink) Old 03-20-2017, 10:19 PM
Senior Member
66/93project's Avatar
Join Date: Mar 2013
Location: El Paso, texas
Posts: 969
I ended up with 480# 1" lowering springs from npd. Spoke to a rep there a to the beginning of my journey and he suggested those. Cars feels nice. Has some roll but I've yet to install my awesome subframe connectors and I know that'll improve feel tremendously. The front suspension doesn't bounce like it would on stiffer springs.

66 coupe | deep impact blue | 17" US Mags Ramblers | DSS 331 | TFS heads/Stage 1 cam | Dynomax Bullet mufflers | 3.80 Trac Lok posi | C4/Shift kit | PA Performance Billet Servo/Finned deep pan | CalTrac bars | 120mm Halo led grill lights | iPad mini Console/hidden pioneer stereo | Enclosed trunk/10" Kicker
Finally completed- working on last bugs....
66/93project is offline  
Sponsored Links

Quick Reply

Register Now

In order to be able to post messages on the Vintage Mustang Forums forums, you must first register.
Please enter your desired user name, your email address and other required details in the form below.

User Name:
Please enter a password for your user account. Note that passwords are case-sensitive.


Confirm Password:
Email Address
Please enter a valid email address for yourself.

Email Address:


Human Verification

In order to verify that you are a human and not a spam bot, please enter the answer into the following box below based on the instructions contained in the graphic.

Thread Tools
Show Printable Version Show Printable Version
Email this Page Email this Page

Posting Rules  
You may post new threads
You may post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are Off

For the best viewing experience please update your browser to Google Chrome