HKS Hyper D coilovers Q?

[R15]

what is the valve at the bottom for?

[atmosports]

Been ages since I looked at a Hypermax D, but I'd be 100% certain it's there to charge the shock up with Nitrogen gas. Gas pressure at a guess as I've never checked a Hypermax D would be in the vicinity of 150-200psi, it could be higher or lower but that's about where most manufacturer's run.

[R15]

so would lessening this amount to say 120 have the effect of sontening the ride slightly?

[atmosports]

It'd have a similar effect to runner a softer spring, how much softer I have no idea without doing all the maths. The only major factor would be if the oil in the shock starts to caviate with the lower gas pressure but I doubt it would make much difference unless you went under 100psi. Just remember if you do try it & want to go back to what you had you'll need to find someone with Nitrogen to up the pressure again. I have no idea if playing with gas pressure will void any warranty etc & too be honest I've normally only changed gas pressure on a race-car as a last ditch effort when I've been short on time to seee if a softer or stiffer spring would work, I've never played with it on a road car I've also just reset them to what the manufacturer uses.