Dampers Function– A shocking introduction
A damper’s (commonly known as a shock absorber) function is to remove kinetic energy from the suspension system and control the spring. To fully understand what’s going on we need to dive a little deeper into the suspension. The damper is 1 of 3 vital parts that make up a vehicle suspension system. The other 2 are a spring and a linkage between the vehicle body and wheel, such as a double-wishbone, pushrods or swingarm etc.
The linkage allows the wheel to move independently from the body which not only improves ride comfort and handling but it also improves traction by keeping the tyre in contact with the ground (the prime function of suspension).
The spring supports the mass of the vehicle body and aids control of body roll. Most importantly, it absorbs any shocks from bumps in the road as kinetic energy. Any uncontrolled release of this energy would cause the vehicle to oscillate and bounce like a pogo stick and this is far from ideal because it breaks traction between the tyre and the ground reducing grip.
The damper controls the spring’s energy release by converting kinetic (movement) energy into heat via friction thereby reducing the amplitude of the oscillation – improving traction. An additional function of a damper is to control the rate/speed of a spring’s movement (extension/compression). Control of this is important as it determines how much a car rolls and weight transfers coming out of a corner and it is very useful for tuning understeer/oversteer out of a car.
Find out more about tuning understeer/oversteer in the adjustable damper article.
So, if the spring absorbs the shock and the damper reduces oscillation (by “damping”), it leaves one vital question… why are dampers commonly called shock absorbers when they clearly don’t carry out that function?
What’s inside the damper
Inside the damper, you’ll find a piston within a sealed oil chamber. One end of the damper is connected to the vehicle body and the other wheel. When the wheel moves up and down, it causes the piston to move which forces the oil to flow through one-way valve ports. The port size and amount of force needed to open the valve, controls the oil flow. By restricting the oil flow, the resistance causes friction turning kinetic energy into heat. Reducing oscillation of the spring “damping”.
On each side of the piston, the ports are covered by a stack of shims creating the one-way valve. These shims are designed to flex under the force of the oil flowing through the opening of the valve, then return to close the valve.
More about damper design, type and which is best for you.
Dampers have two movements: compression and rebound. Compression, also known as bump, occurs when the damper is compressed, such as when hitting an apex curb. When the damper extends, this is known as rebound. Each piston will have a compression face and rebound face within its own valve stack.
Penske Racing Shocks Liner Piston
By increasing the thickness of the shims on the stack, it increases the damping which makes the damper stiffer (hard) and the spring slow-moving with fewer oscillations. Reducing the thickness of the shim stack creates (soft) less damping with a fast-moving spring and higher oscillations. Using a damper dynamometer, a shim stack can be fine-tuned to give precise damping characteristics.
Damping that is too stiff means the suspension will not move easily. Causing the tyre to bounce on an uneven surface breaking traction, reducing grip or interferes with weight transfer because the damper doesn’t extend after it’s compressed. Too soft, and the spring will continue to oscillate because energy is not being removed as quickly from the system which will create a wallowing ride.