I found this equation to calculate 100% critical damping:
2*sqroot(kg*spring in N)
I'm working with a PC game that uses kg for vehicle weight, kN/m springs, and N/m/s dampers. Multiplying the 100% critical value by .55 or .6 for slow damping is giving good results, but I'm not certain if this is accurately giving 55-60% damping ratio. Can anyone confirm if it is, or if not and I need to stop being lazy and learn differential equations? Thanks!