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Types of Shock Absorbers and How They Work

Early motor vehicles were equipped with the same suspension systems that worked so well for horse-drawn carriages. Leaf springs deflected when a wheel hit a bump or hole and prevented the force from rocking the occupants of the vehicle. This type of spring was used because the friction between the leaves prevented the springs from continuing to bounce. This was why helical springs were impractical. That is until the development of the shock absorber.

What a Shock Absorber Does

There are many kinds of shock absorbers for many purposes. For example, a boat owner may use SPD gas springs shocks. As its name implies, a shock absorber absorbs the energy created in a spring when a vehicle hits a bump. This prevents the spring from dissipating its energy by continuing to bounce and makes for a smoother ride.

Types of Shock Absorbers

That are several types of shock absorbers and they use different principles to do their job. The two basic categories are twin-tube and monotube.


A twin-tube shock is made up of two tubes as you may have guessed. They are nested one inside the other. The inner tube is the working tube and the outer is called the reserve tube. There is a small valve at the bottom of the working tube that allows the hydraulic fluid to move in and out of the tube when the shock is depressed. This changes the mechanical energy of the bump into heat energy.

A twin-tube, gas-charged shock, has nitrogen under low pressure added to the reserve tube. This helps prevent the shock from overheating and hydraulic fluid from leaking out. The twin-tube, gas-charged design is the most commonly used shock absorber.


A monotube shock absorber has only one tube, called the pressure tube. There are two pistons and the tube is filled with gas and hydraulic fluid. The pistons are the pressure piston and the floating piston. The pistons move simultaneously and the gas and fluid are kept separated by them. Upon hitting uneven parts of a road, the piston slide in and absorb the energy of the bump. Slowed by the gas and fluid, the mechanical energy is converted to heat energy by the friction and the springs are prevented from bouncing.

The smooth ride you experience in your car happens because of the suspension system. It’s complex and involves several parts working together. Perhaps the most important of these is the shock absorber which lets you leave the bumps behind.