Step 1.
Choose a pair of suitable-sized discs. Place the top disc (bigger hole) and bottom disc (smaller hole) into both ends of the coil spring.
Step 2.
Insert the compressor rod and make sure the rod and plates are interlock firmly with each other.
Step 3.
Fasten the rod by a 19 mm wrench drive until the spring is well compressed.
Do NOT use air tools.
Step 4
Release the spring carefully and install a new one.