Originally Posted by
neil0502
That is normal ... just as you say ... to some extent. It's back-pressure coming from the tire. No surprise, you should see very little of it when inflating a brand new (0 psi) tube.
Glad you're doing more with the pump, now, than just getting that all-too-elusive upper body workout
If the tube is a presta, the back pressure leaking out is from the pump...
not the tire. The pressure inside the tube will close the presta valve unless you depress the plunger.
Schraders do the same except you have to depress plunger and hold it open to get air in them. They fill the hose as soon as you flip the thumb lock on the chuck.