Coilover Spring Rates Explained

One of our specialties is offering custom spring rate options on our coilovers. We often see requests for spring rates in both KG/mm and LB/in. All of our springs will be based off the KG/mm scaling, so we put together a handy chart here to help you convert over your spring rates from the standard scaling. 

Springs are rated in kilograms per millimeter (KG/mm) or pounds per inch (lb/in), which represents the amount of force required to compress the spring 1 MM at its fully extended length. A spring rated at 12 KG/mm will compress 1 MM for every 12 KG of force exerted on the spring. Compressing the spring 2 MM would take 24 KG pounds of force with a linear spring. Conversely on the LB/in scale, it is the amount of force required to compress the spring 1 inch at it's fully extended length. 

For reference, 1 KG/mm is roughly equal to 56 LBS/in.

LB/IN TO KG/MM:

700 lb/in = 12.5 kg/mm

650 lb/in = 11.6 kg/mm

600 lb/in = 10.7 kg/mm

550 lb/in = 9.8 kg/mm

500 lb/in = 8.9 kg/mm

450 lb/in = 8 kg/mm

400 lb/in = 7.1 kg/mm

350 lb/in = 6.2 kg/mm

300 lb/in = 5.3 kg/mm

250 lb/in = 4.5 kg/mm

KG/MM TO LB/IN:

16 kg/mm = 896 lb/in 

15 kg/mm = 840 lb/in 

14 kg/mm = 784 lb/in

13 kg/mm = 728 lb/in

12 kg/mm = 672 lb/in

11 kg/mm = 616 lb/in

10 kg/mm = 560 lb/in

9.0 kg/mm = 504 lb/in

8.5 kg/mm = 476 lb/in

8.0 kg/mm = 448 lb/in

7.5 kg/mm = 420 lb/in

7.0 kg/mm = 392 lb/in

6.5 kg/mm = 364 lb/in

6.0 kg/mm = 336 lb/in

5.5 kg/mm = 308 lb/in

5.0 kg/mm = 280 lb/in

4.5 kg/mm = 252 lb/in

4.0 kg/mm = 224 lb/in

3.0 kg/mm = 168 lb/in

2.0 kg/mm = 112 lb/in