In order to convert kg/mm to lb/in do the following. Multiply the kg/mm amount by 56. So if you kg/mm spring rate is 6 kg/mm Front and 5 kg/mm Rear your lbs/in would be 336 lb/in Front and 280 lb/in Rear. Pretty Simple.

Below is a archive of Spring Rates for various stock and aftermarket springs for the s13 and s14. Enjoy, Please post any additions you may have to this list. Thanks!

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s13 Spring Rates

Stock '92 (from FSM)
Front & Rear: 102 lb/in
Front & Rear: 110 lb/in w/ HICAS

Eibach ProKit
Front: 114-200 lb/in | -1.8"
Rear: 114-148 lb/in | 1.6"

Eibach Sportlines
Front: 137-230 lb/in | 2.2"
Rear: 128-200 lb/in | 2.1"

Suspension Techniques: 1.3" drop
Front: 206 lb/in | 1.3"
Rear: 155 lb/in | 1.3"

5Zigen R-Rate
Front = 2.4-5.2 kg/mm | 134-291 lb/in | 1.3"
Rear = 1.9-5.0 kg/mm | 106-280 lb/in | 1.1"

Tein HA
Front = 6 kg/mm | 336 lb/in
Rear = 5 kg/mm | 280 lb/in

Tein HE
Front = 8 kg/mm | 448 lb/in
Rear = 6 kg/mm | 336 lb/in

Tein RA
Front = 10 kg/mm | 559 lb/in
Rear = 8 kg/mm | 448 lb/in

Tein RE
Front = 10 kg/mm | 559 lb/in
Rear = 8 kg/mm | 448 lb/in

Tein RS
Front = 10 kg/mm | 559 lb/in
Rear = 8 kg/mm | 448 lb/in

Tein FLEX
Front = 5 kg/mm | 280 lb/in
Rear = 4 kg/mm | 224 lb/in

Tein S.Tech
Front = 3.2 kg/mm | 179 lb/in
Rear = 2.9 kg/mm | 162 lb/in

Zeal Function B-6
Sreet Spec:
Front = 6 kg/mm | 336 lb/in
Rear = 5 kg/mm | 280 lb/in
Circuit Spec:
Front = 8 kg/mm | 448 lb/in
Rear = 7 kg/mm | 392 lb/in

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s14 Spring Rates

kg/mm DR21
Front = 4.8-3.0 kg/mm | 269-168 lb/in
Rear = 4.0-2.8 kg/mm | 224-157 lb/in

kg/mm DR Racing
Front = 6.6-3.2 kg/mm | 370-179 lb/in
Rear = 5.2-2.4 kg/mm | 291-134 lb/in

RSR Hard Springs
Front = 5.0 kg/mm | 280 lb/in
Rear = 4.2 kg/mm | 235 lb/in

TANABE SuperH
Front = 3.0 kg/mm | 168 lb/in | -28mm
Rear = 4.0 kg/mm | 224 lb/in | -9mm

TRUST Sport Springs
Front = 2.6 kg/mm | 146 lb/in | -25mm
Rear = 2.6 kg/mm | 146 lb/in | -25mm

HKS Super Sports
Front = 4.14 kg/mm | 232 lb/in
Rear = 3.46 kg/mm | 194 lb/in

Tein HA kg/mm
Front = 6 kg/mm | 336 lb/in
Rear = 5 kg/mm | 280 lb/in

Tein HE
Front = 8 kg/mm | 448 lb/in
Rear = 6 kg/mm | 336 lb/in

Tein RA
Front = 10 kg/mm | 559 lb/in
Rear = 8 kg/mm | 448 lb/in

Tein RE
Front = 10 kg/mm | 559 lb/in
Rear = 8 kg/mm | 448 lb/in

Tein RS
Front = 10 kg/mm | 559 lb/in
Rear = 8 kg/mm | 448 lb/in

Tein FLEX
Front = 6 kg/mm | 336 lb/in
Rear = 5 kg/mm | 280 lb/in

Tein S.Tech
Front = 4.8 kg/mm | 269 lb/in
Rear = 4.4 kg/mm | 246 lb/in

Zeal Function B-6
Sreet Spec:
Front = 6 kg/mm | 336 lb/in
Rear = 4 kg/mm | 224 lb/in
Circuit Spec:
Front = 8 kg/mm | 448 lb/in
Rear = 6 kg/mm | 336 lb/in

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Anyone know the spring rates for stock S14s, base and SE?

S-14

Apexi N-1 Coilovers
Front = 8 kg/mm | 448 lb/in
Rear = 6 kg/mm | 336 lb/in

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Whiteline Springs, parts 70055 and 70049

Front: 155Lbs/in | 35mm
Back: 165Lbs/in | 40mm

S13

KGMM S21 Sport
front: 3.2 kg/mm | 179.2 lb/in
rear: 2.6 kg/mm | 145.6 lb/in

KGMM S21 SuperSport
front: 4.6 kg/mm | 257.6 lb/in
rear: 3.8 kg/mm | 212.8 lb/in

KGMM S21 Racing
front: 6.6 kg/mm | 369.6 lb/in
rear: 5.2 kg/mm | 291.2 lb/in

Stock 1990 (from FSM):
Front & Rear: 112 lb/in (base)
Front & Rear: 123 lb/in (sports package)

RS*R race springs
5.00kg F and 4.5kg R

Linear Springs for S13

Tokico
Spring Rate - F : 3.0 kg/mm | 169 lbs/in
Spring Rate - R : 2.7 kg/mm | 150 lbs/in
Ride Height - F : -1.0 (expect -1 ~ 2 inch range)
Ride Height - R : -1.0 (expect -1 ~ 2 inch range)

RS-R Down
Spring Rate - F : 3.0 kg/mm | 167 lbs/in
Spring Rate - R : 3.0 kg/mm | 167 lbs/in
Ride Height - F : -1.5 est. (95-98 240sx drop)
Ride Height - R : -1.2 est. (95-98 240sx drop)

Tein S-tech (I think the ones in the first post are incorrect - I got these from Tein's website)
Spring Rate - F : 3.7 kg/mm | 207 lbs/in (MFG #'s)
Spring Rate - R : 3.2 kg/mm | 179 lbs/in (MFG #'s)
Ride Height - F : -1.5" (MFG #'s)
Ride Height - R : -1.2" (MFG #'s)


Progressive Springs for S13

H & R Sport
Spring Rate - F : 2.0~2.08kg/mm | 112~116 lbs/in
Spring Rate - R : 2.5~2.6kg/mm | 140~145 lbs/in
Ride Height - F : -1.3" (MFG #'s)
Ride Height - R : -1.3" (MFG #'s)

S13

Nismo S-Tune (not height adjustable)
_ _ _Front: 5.3 kg/mm | 296 lb/in
_ _ _Rear: 3.9 kg/mm | 218.4 lb/in

Nismo N1
_ _ _Front: 8/10/12 kg/mm | 448 - 672 lb/in
_ _ _Rear: 8 kg/mm | 448 lb/in