This is probably a basic question but I have searched a bit and cannot find a great answer.
This is my first set of tires with Presta valves, and I think I am using them incorrectly.
After I pump up a tire using a floor pump with a presta valve I seem to get a lot of air escaping when I remove the chuck from the valve. I experimented by pumping it up to 120, removing the chuck (and hearing the "woosh" of air when I pulled it off), then re-attaching the chuck. The reading was almost 105. So I lost 15 psi from removing the chuck? Is that normal? Is the chuck broken (brand new Specialized Airtool Pro)? Am I doing something wrong (likely!!)? When the guy in the LBS showed me how to use the pump he got the same air escaping sound when he pulled the chuck off, so I assume it is normal.
Thanks to anyone who can help me here...