KW damping and valve technology, 2-way

KW\’s adjustable dampening technology is offered for a wide selection of applications and vehicle class categories.




Damper Basics – The function of a shock absorber

A shock absorbers job is to subside vibrations caused by the wheels, axles, and body. So the technically correct name for it would be a vibration damper. When driving over irregularities, the created shock or vibrations are absorbed by the suspension.

The spring wants to absorb and release stored energy. In a short sequence of these repetitive processes, a vibration arises. These movements are transmitted via the piston rod to the shock absorber. Here the kinetic energy is converted to heat by hydraulic resistance in the shock absorber valve and reduces the vibrations to an inaudible minimum.




  • Rocking of the body at successive irregularities
  • Gasp or strong immersion during acceleration or braking
  • Jumping wheels
  • Swerving when braking
  • Spinning in corners with a lacking tracking



The shock absorbers used in vehicles are usually twin-tube dampers or mono-tube dampers. A piston moves in an oil-filled cylinder in both damper types. The piston forces the oil through the valves, which creates resistance to the oil flow with the help of various holes and orifices.

During rebound, the oil flows from the outer tube back into the inner tube. In addition to the channels in the bottom valve, the oil also has to flow through the rebound valve located at the piston rod, to get into the piston housing.




How a KW twin-tube shock absorber functions

When a car deflects while driving, the oil which is slightly under pressure, will be displaced by the immersion of the piston rod. It flows into the outer tube through the bottom valve (compression valve) which controls the flow speed.







The spring wants to absorb and release stored energy. In a short sequence of these repetitive processes, a vibration arises. These movements are transmitted via the piston rod to the shock absorber. Here the kinetic energy is converted to heat by hydraulic resistance in the shock absorber valve and reduces the vibrations to an inaudible minimum.




Rebound adjustment

Independent adjustable rebound damping






Rebound adjustment by an allen key



Rebound adjustment by attachable adjustment knob, when space allows



Rebound adjustment by integrated adjustment wheel







16 Clicks – Best perfomance and easy adjustment

KW Variant 2 and KW Street Comfort coilover kits provide 16 clicks of rebound adjustment.
Rebound adjustments can be made to reflect more dynamic driving characteristics or complement a change in tire selection like a different set of tires or winter tires.
The Variant 2 coilover provides the user more then just the height adjustability of a coilover it. The adjustable rebound feature allows the user to dial in a more sportier tighter handling characteristic or a more compliant comfortable setting suitable.




Technical details of adjustable rebound damping


Oil flow during “hard” rebound stroke



Bypass orifice with closed adjuster position. Digressive damping characteristic and the maximum achievable rebound damping. Damping is determined by the setup specific preload of the valve spring at the piston.

The result:
A firm but not a hard rebound stroke adjustment avoids rolling- and pitching motions.

Oil flow during “soft” rebound stroke



Bypass orifice with open adjuster position allowing for a progressive damping characteristic and ability to achieve minimum possible rebound damping .The bypass oil volume (black arrows) is not available anymore for the spring preloaded valve at the piston and the damping.

The result:
A lower rebound damping increases the driving comfort.



Graphic representation of the relation from damper speed (m/s) to damping force (N) when adjusting the rebound damping.




Compression adjustment

Individually adjustable compression damping






Spring plate

The KW spring perch is a completely underrated component. It not only holds the helper spring and main spring at the right position, but it also minimizes the vibration noise of the springs. Depending on the vehicle type and application, KW manufactures the spring perch of high quality aluminum alloy or a polyamide composite material. Whether made of aluminum or the composite material which is also rust resistant, the spring perch which is painted in the typical KW purple is very light weight.

Helper spring

The so-called helper spring is made of high quality chrome silicon steel in flat wire design. It keeps the main spring above the polyamide spring perch under tension, no matter what level of lowering. As soon as the weight of the vehicle presses on the helper spring, all windings are pressed together – the spring “goes on block”.

Polyamide intermediate ring

The intermediate rings made of a light poyamide composite material used by KW not only hold the springs, but also minimize the vibration noise of the springs. Furthermore they isolate the rolling noices of the body.

Bump stop with integrated dust protection system

The dust cover prevents water and dirt particles reaching the piston rod seal package. Depending on the manufacturer, the dust cover is made of elastomer plastic and also serves as a passive suspension element.

Linear spring rate

If a suspension spring is winded linear, the force increases in direct proportion to the compression travel. A spring rate of 70 Newton (N)/mm means that 70 N must act on the spring to compress it by one millimeter.

High strength main spring

Progressive spring rate

At a progressive spring rate, the suspension spring consits of differently strong spring windings. When a force acts, the weak windings give up at first and then the stronger spring windings. The same effect can also be achieved by the use of two springs placed on top of each other.

The high-strength spring made of chrome-silicon steel is vehicle specific adjusted in the respective suspension damper in its spring rate for long life it is multicoated. It is also called the main spring at coilovers. With brands such as KW, the spring “sits” after years just minimally.

Suspension spring

Not only the damper or vibration shock absorber of a KW coilover kit affects the springing behaviour but also the KW spring does. The resulting kinetic energy is stored by the spring during compression and converted into heat energy from the damper.

The spring rate tells the amount of force (N) that has to act to the spring, so that it immerses by a millimeter. Simply explained: the higher the spring rate, the stiffer the spring, and the more force must act on the spring to compress it.

Composite collar for height adjustment

KW uses a threaded ring made of a resistant polyamide composite material with a stainless steel insert. Even if dirt particles such as brake dust or sand grains hit the polyamide collar will not be damaged. If anodized aluminum spring perchs are used after repeated lowering adjustment friction of any contamination may cause microcracks on the anodized surface. If the unprotected aluminum threaded ring directly touches the steel or stainless-steel strut thread oxidation will occur. In the worst case, height adjustmant will now not be possible anymore. With the durable KW coilovers in inox-line and the used polyamide collar, this is not the case.

Stainless steel “inox-line” strut housing with integrated shock absorber

The strut housing of KW coilovers are made of high quality stainless steel and are an investment for the entire life of the car. At all weather conditions, the stainless steel KW coilovers are 100 percent corrosion resistant and have an unlimited life.

The functioning of lowering via the dirt-resistant trapezoid thread and the composite collar is designed for long use. During a salt spray test, there was no oxidation of the KW coilover struts. So even after years, the lowering is not affected.




KW damping technology in detail

KW damping technology in detail – Function of KW twin-tube dampers

When a car deflects when driving, the oil which is lightly under pressure, will be displaced by the immersion of the piston rod. It flows into the outer tube through the bottom valve (compression valve) which controls the flow speed. During rebound, the oil flows from the outer tube back into the inner tube. In addition to the channels in the bottom valve, the oil also has to flow through the rebound valve located at the piston rod, to get into the piston housing.

The damper of a suspension kit converts the kinetic energy of the suspension spring into heat energy and passes it into the environment. When driving a curve, the KW coilover kit works in the curve inside of the vehicle in rebound and in the curve outside in compression damping.







What does the rebound have influence on?

The rebound damping directly affects the operating speed of the piston rod rebound springing and the expansion rate of the suspension spring. So it also determines how fast the suspension spring is expanded back in their original position. At the KW coilovers Variant 2 and 3, the driver can adjust the rebound via 16 precise clicks.

So the diameter of the rebound valves will be opened for a softer driving behaviour and closed for a tighter setup. With the adjustable rebound of the KW coilovers, the vehicle handling and comfort can be influenced.