Originally Posted by
JerrySTL
Both a presta and schraeder valve should close almost instantly once the chuck is removed unless it gets hung up. The air that you hear escaping is from the pump and hose.
How are you checking for the pressure drop? If using the pump's gauge, air filling the hose is enough to drop pressure. If using a pencil gauge, it's pretty easy to bleed off air before getting a reading. Plus those pencil gauges aren't very accurate. As a matter of fact, pump gauges aren't that accurate. I had a pump that read 20 PSI low at 100 PSI. In other words, it said 80 PSI.
As long as 'slightly over inflate' doesn't exceed the tire or rim recommendations, I'd recommend just doing that.
Part of the problem might be from the chuck being hung up, and any amount of air that does escape from the tube depletes the pressure quit a bit considering that we are dealing with a small tube size. I didn't notice such a problem with the 26" tubes of my MB.
I agree, those pencil gauges do present a problem and they pretty much just give you a ball park figure. I have a pretty decent gauge, but the problem I'm having is that with the cramped room on the small wheels I find it difficult to get the gauge on/off the valve without letting some air out, and some air in a small tire tends to be a lot regarding pressure. I'm thinking that having a pump where you can remove the pressure in the hose will allow for a much smoother removal of the chuck. Well at least I'm hoping.