There's a listing of the spring rates that was posted by Duffy floyd on sccoa, with all the spring rates:
The Thunderbird spring rates are listed by year and application
below.
Year |
3.8L |
3.8L SC |
V8 |
1989 |
Front: 223-282 lb./in.
Rear: 361-501 lb./in. |
Front: 349-403 lb./in.
Rear: 509-637 lb./in. |
N/A |
1990 |
Front: 223-282 lb./in.
Rear: 361-501 lb./in. |
Front: 349-403 lb./in.
Rear: 509-637 lb./in. |
N/A |
1991 |
Front: 223-282 lb./in.
Rear: 361-501 lb./in. |
Front: 349-403 lb./in.
Rear: 509-637 lb./in. |
Front: 270-330 lb./in.
Rear: 361-501 lb./in. |
1992 |
Front: 223-282 lb./in.
Rear: 361-501 lb./in. |
Front: 349-403 lb./in.
Rear: 509-637 lb./in. |
Front: 270-330 lb./in.
Rear: 361-501 lb./in. |
1993 |
Front: 223-282 lb./in.
Rear: 361-501 lb./in. |
Front: 349-403 lb./in.
Rear: 509-637 lb./in. |
Front: 270-330 lb./in.
Rear: 361-501 lb./in. |
1994 |
Front: 223-282 lb./in.
Rear: 361-501 lb./in. |
Front: 349-403 lb./in.
Rear: 509-637 lb./in. |
Front: 270-330 lb./in.
Rear: 361-501 lb./in. |
1995 |
Front: 223-282 lb./in.
Rear: 361-501 lb./in. |
Front: 349-403 lb./in.
Rear: 509-637 lb./in. |
Front: 270-330 lb./in.
Rear: 361-501 lb./in. |
1996 |
Front: 223-282 lb./in.
Rear: 361-501 lb./in. |
N/A |
Front: 270-330 lb./in.
Rear: 361-501 lb./in. |
1997 |
Front: 223-282 lb./in.
Rear: 361-501 lb./in. |
N/A |
Front: 270-330 lb./in.
Rear: 361-501 lb./in.
LX Sport Option:
Front: 349-403 lb./in.
Rear: 509-637 lb./in. |
Definitions:
Progressive Springs: Also know as rising-rate springs or variable springs are like two springs in one. The first small amount of suspension travel gets the softer rate, which helps filter out potholes, bumps, expansion joints, and ruff road surfaces. After the first inch of compression the spring rate switches to the higher, stiffer rate.
Linear Springs: A linear-rate spring is designed with an amount of resistance in its first inch of compression that doubles with the next inch of suspension compression, triples with the next inch, and so on.
Free length: Free length is the height of the spring uncompressed.
Front and rear stock anti-sway bar information is available.
Click
Here
Eibach
Eibach-ProKit springs are of the progressive design and offer chrome silicon heat treated steel that is powder coated for a lifetime of protection. Eibach offers two versions of their ProKit for the 89-97 Thunderbird.
One is designed for the v6 3.8L normally aspirated (
part#3522.140) and is designed to lower the car
1.25" with a front spring rate of
286-411 lbs per inch and a rear spring rate of
514-714 lbs per inch. The free length of the springs are
16.375" for the front and
11.625" for the rear.
The other ProKit is designed for the v8 & Super Coupe (
part#3524.140) and is designed to lower the car
1.50" with a front spring rate of
286-411 lbs per inch and a rear spring rate of
514-714 lbs per inch. The free length of the springs are
16.125" for the front and
11.4375" for the rear.
Eibach makes their springs in the USA and the average discounted price for the springs are around $225.00 - $250.00 and come with a lifetime warranty against defects in workmanship and materials.
H&R
H&R springs are of the progressive design and are made from Bekaert wire from Belgium. The Bekaert wire is used exclusively because in durability testing, the Bekaert wire alloy has a much longer service life than any other wire tested. These materials ensure a defect-free function over the entire service life. H&R offers two versions of their Sport Springs for the 89-97 Thunderbird. One is designed for the V6 3.8L normally aspirated (
part#51623) and is designed to lower the car
1.60" in front and
1.40" in the rear with a front spring rate of
310-385 lbs per inch and a rear spring rate of
540-610 lbs per inch. The free length information was not available.
The other Sport Spring is designed for the V8 & Super Coupe (
part#51624) and is designed to lower the car
1.50" in front and
1.40" in the rear with a front spring rate of
310-385 lbs per inch and a rear spring rate of
540-610 lbs per inch. The free length of the springs are
16.25" for the front and
12.00" for the rear.
H&R makes their springs in Germany and the average discounted price for the springs are around $225.00 - $250.00 and come with a lifetime warranty against defects in workmanship and materials.
H&R Special Springs, LP
3815 Bakerview
Spur #7
Bellingham, WA 98226
Tel. 888-827-8881
(360) 738-8881
fax: (360)738-8889 |
Tokico
Tokico-Sport Lowering Springs are of the linear design and offer cold wound steel that is powder coated for a lifetime of protection. Tokico offers one kit for the 89-97 Thunderbird and it is designed to lower the car
1.25". The front spring rate is
326 lbs per inch and the rear spring rate is
577 lbs per inch with a free length of
15.70" in front and
11.07" in the rear.
Tokico makes their springs in the USA and the average discounted price for the springs are around $225.00 - $250.00 and come with a lifetime warranty against defects in workmanship and materials.
Tokico
1330 Storm Parkway
Torrance, CA 90501
Tel. (310) 534-4934 |
Suspension Techniques
Suspension Techniques-Sport Sport Suspension springs are of the linear design and offer cold wound steel that is powder coated for a lifetime of protection. Suspension Techniques offers one kit for the 89-97 Thunderbird and it is designed to lower the car
1.50". The front spring rate is
432 lbs per inch and the rear spring rate is
631 lbs per inch with a free length of
14.33 in front and
10.89" in the rear.
Suspension Techniques makes their springs in the USA and the average discounted price for the springs are around $220.00 - $250.00 and come with a lifetime warranty to the original purchaser of the product that it will be free of manufacturing defects so long as such purchaser owns the vehicle on which such products were originally installed. The warranty is transferable by the original purchaser for a warranty period of five years from the original purchase date.
Suspension Techniques, Inc.
(A Belltech Company)
2822 East California Avenue
Fresno, California 93721
Phone: (800) 595-7016
California and outside US: (209) 266-9173
Fax: (209) 266-4348
http://www.belltechcorp.com |
Jamex
Jamex-Sport Springs are of the progressive design and offer chrome-silicon heat treated steel that is powder coated for a lifetime of protection.
Jamex offers one kit for the 89-97 Thunderbird and it is designed to lower the car
1.50" - 2.00".
The spring rate is listed as
15% stiffer than the OE V8 sport springs with a free length of
17.00" in front and
11.50" in the rear. Jamex makes their springs in the USA and the average discounted price for the springs are around $125.00 and come with a lifetime warranty against defects in workmanship and materials.
Jamex
4975 C Energy Way
Reno, Nevada 89502
Tel. (702)857-4888
Fax (702) 857-1635
http://www.jamex.com |
Vogtland
As of 2021 Vogtland is the last aftermarket manufacturer making lowering springs for the Thunderbird.
Vogtland makes progressive rate spring in two sizes for the MN12 that are available in either a 1" drop or 1.6" drop. They have a gorgeous violet color like no other spring color on the market.
Vogtland North America is well know for it's involvement in NASCAR suspension technology. The quality of these springs are unmatched and highly superior to other springs available. The price tag for a set of MN12 springs is approx. $260.
The springs need to be broken in for a short period of time before they will settle exactly right. They should be set after about a week on the car.
www.vogtland.com
1" Vogtland: 315-412 front/530-650 rear
1.6" Vogtland: 365-400 front/600-713 rear
This came up when I was deciding on what springs to put on Lazarus. I went with the sport springs; the gg springs are softer, and ff are even softer. If it's not obvious, the 33gg are the ratings for front and rear, With the fronts heavier to take up for the engine.