Softer Shock absorber options
Explain...inquiring minds want to know! Please compare the KYB to the Bilstein
I'm sure
@72bluNblu or
@BergmanAutoCraft could explain it better but I'll give it a shot...
The first key thing to understand when dealing with shocks is that every vibrating system has a "natural frequency". This depends on the unsprung weight (wheel and tire, brakes, spindle etc for front or the entire rear axle), sprung weight (car itself) and the rate or stiffness of the spring. The system needs to have damping (shock absorbers on a car) in order to stop it from vibrating virtually forever or having the tires leave contact with the pavement and the required damping rate is based on the natural frequency. If the damping rate is too low (shocks are too soft) the car will bounce a lot after hitting bumps and have bad recovery time when making sharp turns. If it's too high the car will ride stiff and the springs won't be able to do their job properly.
So with that said different cars in different conditions need shocks with different damping rates. Unfortunately for classic Mopars you basically have cheap shocks that are either very soft/low damping rate to match up with factory spring rates or too firm like the KYBs. The higher-end shocks like Bilsteins in a nutshell have better control and react to different conditions better, as in going over potholes vs. driving fast on a twisty road because the way they work internally is more sophisticated. This is why adjustable shocks exist; when you want maximum suspension control you can dial-in the damping rate to match up with the spring rate and driving conditions. I actually plan to get adjustable shocks for my Duster since I do handling-oriented amateur racing stuff with it and the current stock replacements don't do jack with my 1.14" torsion bars, front and rear sway bars and Hotchkis rear springs.
KYB Gas-a-justs are good-quality shocks but they have progressive valving meaning the damping force is highest when the wheel is moving fast (over bumps or potholes) which is the opposite of what you want. In my experience they work best on trucks and 4x4s with big tires and lots of unsprung weight to keep things bouncing around too much. Bilsteins or other brands of high-performance car shocks have digressive valving which work the opposite; soft going over bumps but firms things up in hard cornering to keep the car stable and minimize unwanted weight transfer, like body lean.
So to the OP after all that, lol... if you just like to cruise your car and aren't concerned with making it handle super well go with some cheap Monroes or Gabriels, your ride will be much softer. Only downside in my experience is they're built like crap and like to blow out after not very long. I've had shocks from both brands go out within months of installing them. I know KYB makes an OE-replacement line of shocks called Excel-G which do ride soft, I've used them on other vehicles but I'm not sure if they have them in the right sizes for classic Mopars. In the past when I've searched by year/make/model for my Duster the Excel-G's didn't come up.
