What he said^^.If your shock valve and pump work properly the air you hear escaping is the air pressure remaining in the tubing and gauge of the pump bleeding off the pump and not the shock. Although their is still probably a very tiny amount loss during the disconnect.
When you reconnect the pump you will see a lower pressure than when you originally disconnected it. This is because some of the air from the shocks air can is transferred back into the tube and gauge of the pump. The "loss" you are seeing in the pressure reading is actually from the shock pump increasing the volume of space the air must occupy when the pump is reattached.
No you seem to be missing the point of 2obscura. When you reconnect the pump you will get a lower reading then what was actually in the fork/shock. This is because when you had for example 100psi in your shock and you connect the pump the volume increases and the pressure reduces to perhaps 90psi. Ok, at that moment there is 90psi in your shock but it used to be 100psi before you connected the shock.What he said^^^
So when you reconnect, it gives you the pressure in your fork.
Oh great, more things that needlessly require batteries.I bought this one it is simply awesome. I use for my fork,rearshock, dropper post and setting my tire pressure via a presta valve adapter.
Its a moto crossover product...
Solidly made, not too heavy to carry in my pack and"replaceable battery unlike foxes digital shock pump"
Works Connection - Digital Shock Pump - BTO Sports