I have seen a lot of youtube clips on how to fill a presta valve, but none seem to address this issue. First of all, is there a way to check the pressure on a presta valve with an air pressure gauge? I bought a floor pump with a gauge on it but I'm still wondering how you know if you have the right pressure. When I inflated the tires on my old bike (car valves) I would usually over inflate a little and then as I checked the pressure with the air gauge the tire would lose a few pound each time I check it until I got it down to the right pressure (65 lbs) If I check it one more time it would be under inflated and I would have to start all over. So I’m wondering, if I attach the air pump and inflate to 120 lbs, doesn’t the tire loose some pressure when I remove the air pump? Should I over inflate a little to compensate for this? How do I know if my tires are at the right pressure?