Method of changing damping characteristics of twin-tube shock absorber

A method of changing damping characteristics of a twin-tube shock absorber, comprising:

• a hole formation step of forming a hole in an outer tube of the twin-tube shock absorber;
• an oil draining step of draining oil from the inside of the twin-tube shock absorber to the outside through the hole, the oil draining step being performed after the hole formation step;
• an outflow prevention valve mounting step of mounting in the hole an outflow prevention valve for preventing a fluid from outflowing from the inside of the twin-tube shock absorber to the outside through the hole, the outflow prevention valve mounting step being performed after the hole formation step;
• a replacement oil charge step of charging replacement oil from the outside of the twin-tube shock absorber to the inside through the hole, the replacement oil charge step being performed after the oil draining step;
• a gas sucking step of sucking a gas from the inside of the twin-tube shock absorber to the outside through a flow channel of the temporarily opened outflow prevention valve in a state that the outflow prevention valve is positioned on the upper side in the twin-tube shock absorber, the gas sucking step being performed after the replacement oil charge step and the outflow prevention valve mounting step;
• and
• a replacement gas injection step of injecting a replacement gas from the outside of the twin-tube shock absorber to the inside through the flow channel of the temporarily opened outflow prevention valve in a state that the outflow prevention valve is positioned on the upper side in the twin-tube shock absorber, the replacement gas injection step being performed after the gas sucking step.