I have a Blackburn entry level dual head floor pump. I usually pump up my presta valve/tires to 105 psi. I noticed that when I remove the head, some air still comes out, no matter how quickly I try to remove the pump head. I wondered how much air I am losing here, so I ran a test. After pumping to 105 psi and removing, I re-attached the pump head and locked down with the lever. No air came out at this time, however I noticed that there is no reading on the pump. I then raised the pump handle to max and depressed one time. The reading then came up to 95 psi. I am losing 10 psi by just removing the pump head? I know on a presta valve that you have to unscrew the cap and then if you press down , air will quickly escape, but is this normal for my pump not to read until I pump one time? Thanks.