HKS SUSPENSION is for great driving performance and very comfortable ride.

HKS’s suspension is Single Tube type design. We think this is the best suspension structure for a sport, street, and comfort in driving. It will have ideal traction in all kinds of street for both performance and comfortable driving. HKS suspension is all Single Tube type and made in our factory which produce a best product in quality.

Single VS Twin

Twin tube damper has some problems such as cooling problem, vacuum problem in gas room caused by piston stroke and bubbles due to mixed air with oil. Because of these problems, it is hard to keep damping force. With gas type single tube structure of HKS, all above problems are solved. HKS gas type single tube structure removes outer case of twin tube. Gas and oil rooms are divided. The gas room absorbs capacity change of oil room due to piston stroke. Damping force occurs when oil flows through piston valve and it is controlled with the valve. Free piston moves up and down by gas pressure, and it divides oil and gas completely. Thus, oil room is always pressured to prevent bubble or vacuum problems.

Aeration & Cavitation

Single tube type can divide “Oil room” and “Gas room” so that it can prevent *Aeration and *Cavitation, which are common problems of twin tube type. Single tube damper has proper damping force for steady and comfortable ride that we cannot feel with twin tube damper.


Problem that air is mixed with oil. Air contacts to valve and makes noise.


Air in oil due to aeration or any other reasons, expands and becomes bubble because of rapid pressure drop. If cavitation happens, it is very hard to have proper damping force.

Piston area, Valve, Orifice(hole)


Single tube type are able to have larger piston area.* Because of larger diameter of piston and improved orifice, it reacts subtlety against even slight input from road. That is why, single tube type can eliminate road shock that twin tube cannot and it delivers comfortable ride and quick response handling.

 * It is not only increased area, but every part need to work properly for best damper performance. Thus, the piston needs to be proper size.



Cylinder of single tube type faces to air directly for better radiation than twin tube. Oil life will be longer.
Product Performance will not change for long time. Thus, users can feel “Performance of single tube and difference from twin tube type” for long time.

* Oil is damaged earlier when it is used under hot temperature or mixed with oxygen (air).

Inverted type

It is not possible to design inverted layout for twin tube type. With inverted layout, suspension will be stronger and it helps better handling and to have more information from road. Stability is also improved.

* Shock absorber of strut type suspension works as a part of suspension link. Thus, to increase strength of suspension, shock absorber needs to be inverted.

* Damping force — The force to reduce vertical vibration of car body. Evaluation of damper itself is the timing and volume of damping force.

* Inverted type and Normal type — Piston of Inverted type shock absorber is located at lower position and cylinder is above. Normal type is opposite.