Using compressor gauge to determine tyre pressure? I own one of these "pistols" used with compressors, but have no idea on how to use them to determine the pressure inside my (tubeless) tyre.

When I inflate my tyre the values on the gauge get immediately to 80 psi, which, I believe, is the average pressure in the whole tyre+compressor tank system?

Thanks in advance.
The little thing you operate with your finger controls a valve, opening the circuit from the compressor to the tire. Once you release the trigger, the valve is closed and the gauge will measure the pressure in the tire and in the little hose connected to the tire (if the connection to the tire valve is tight). The compressor will be isolated by the valve.

So, what you have to do is:


connect the hose to the tire valve
pull the trigger for a short time
release the trigger
read the pressure
if the pressure is not enough go back to 2


What you don't do is:


pull the trigger for long time: you are not inflating a car tire. The first time I let somebody use it for inflating my tires, I ended up with an exploded tube (they were used to inflate car tires)