Similar to the insufficient stroke problem, the high-pressure gas injection creates a stiffer ride, enlarges friction etc. and is the main reason for deteriorating ride quality.
Some manufacturers have the base valve positioned above the free piston to lower the high-pressure gas injected. But this results in even further sacrifice in stroke space and a tendency to reverse the effect.
【Reference】 Why the mono-tube requires high pressure gas injection.
The twin-tube shares and creates the expanding/ contracting damping force with the piston and base valves, so there is no need for high-pressure gas injection.
However, the mono-tube creates the expanding/ contracting damping force with just the piston valve.
The mono-tube stroke action occurs when the free piston moves in the space created by the contracting piston rod. During this action, if there isn’t enough pressure on the free piston, it will easily move, over contracting and accurate contracting damping force will not be achieved.
For this reason, there needs to be enough high-pressure gas injected into the gas chamber to control the free piston.
When you inject high-pressure gas into the gas chamber, according to Pascal’s law, there will be an equal amount of gas pressure supplied to the amount of shock sustained. When this happens there will be high pressure applied on the oil seal, and the restraining force on the seal will increase therefore also increasing friction.
