do you use coilovers? It's how I determine the rates - on my race car I would run 6kg front /4kg rears on the street - 8/6kg was about as stiff as I'd like on the street and 10kg/8kg was racing pavement
right now I have 1.12 torsion bars rated at 248 and leaf springs at 200 (hotchkis is 170 for comparison) 3.5kg and 4.4kg respectively
The best way I found if you want to convert to kg rates is here:
https://www.redline360.com/garage/spring-rate-conversion-chart-easily-convert-kgmm-to-lbsinbasically divide by 56 to get the rate - I find it to be pretty close ride wise - there is other factors to consider like havinga big block up front vs a small block - I'd like to go with higher rates now that I've driven it the past few years, I took peoples advice and went withthe safer 1.12" bars I should have gone with the 1.24" I
