I use the Novara tubes too. I think they are made by kenda and I know their valves stick. I tap the valves to let some air out first then start pumping. Usually the pressure builds up in the hose so that my guage reads over 100 and then the valve pops audibly. At that point the pressure guage drops to whatever the actual pressure in the tire is (usually 80 something before I top them off) and you can pump your tires up. I don't know that any other valve will work any better but I would like to try Schwalbe's which I hear don't lose pressure for a long time.