The ride comfort of your car depends on a combination of things in your car's suspension system. The most obvious of these is the condition and type of shock absorber used, but tire size and shape, spring stiffness and anti-roll bar stiffness also affect how your car handles bumps, turns and dips. In general, changing a car's suspension to increase its performance and handling characteristics will decrease ride comfort, and vice versa. The key is to find a compromise that meets your needs for both comfort and handling.
Replace your car's shock absorbers with new gas shock absorbers. Shocks can wear out over time, causing a rough ride. Gas shocks are more forgiving than hydraulic shocks over bumps and potholes.
Choose new tires with a higher sidewall than your current tires. Low-profile tires (with a short sidewall) do not flex very well when they hit a bump, which transfers shock to the rest of the suspension system.
Replace the springs in your suspension with softer springs. If handling around curves is a concern, choose progressive springs, which are soft under light compression and stiff under heavy compression. Otherwise, choose soft linear springs, which have a consistent response regardless of compression.
Add an anti-roll bar designed for regular road use if your car does not have one. Avoid stiff anti-roll bars designed for racing, which increase cornering performance but decrease ride comfort. An anti-roll bar will reduce vehicle sway around corners.
Shock absorbers, springs and anti-roll bars do not have a standardised rating system describing stiffness. Ask a trusted mechanic to recommend the softest, most comfort-enhancing models or read the descriptions in a manufacturer's catalogue or on their website. The first two numbers in a tire size description refer to the width in millimetres and the aspect ratio as a percentage. Divide the second number by 100, then multiply the result by the first number to determine the height of the sidewall in millimetres.
Changing your car's suspension system can alter the handling in unexpected ways. Drive cautiously after such alterations.