Types of Shock Absorber

In common, there are 2 types of shock absorber which is oil shock-absorber and gas shock-absorber. Oil shock-absorber more comfortable compare to gas shock-absorber. Gas shock-absorber not contains 100% gas, it has oil act as the lubricant. To differentiate oil and gas shock-absorber when you want to purchase it, you can press the stalk. If it is oil type, the stalk will not back to the position when you press it down. The stalk that can go back to its previous position will definitely gas shock-absorber.
Some aftermarket shock-absorbers have double action type. This means the shock-absorber will faster the rebound action but this type of shock-absorber will wear out faster. Double action and single action shock-absorber is just talking about the percentage between the compress action and rebound action. Single-action shock-absorber has the ratio of 40% compress and 60% rebound.. Double-action is the vice versa. The higher the percentage, the more the action can hold-up. So when rebound action, spring will be helped by shock-absorber and it make the car back to its position faster.
Base on the design, shock-absorber have monotube and twin-tube design. For the car that giving high priority for comfortability and durability, twin-tube is the best choice. The more you give pressure for the twin-tube shock-absorber, the higher the hardeness level. This characteristics make same comfort when you have full passenger in your car or when you do self-driving. Monotube has same hardeness level in any pressure which means if you think your car is the most comfortable when have 3 passengers, then when you drive yourself it will be too hard and when you have full passengers it will be to soft. So the recommended one is twin-tube shock-absorber.
Now, there is self-leveling shock-absorber in the market. It makes you able to settle the hardeness level of the shock-absorber.
See also The Sign When You Need to Change Shock Absorber
You can read other useful tips about car in this site by clicking here.