lock nut is on my Presta to rim as well. I cannot understand how the air is leaking unless there is a burr that cuts a channel for the air to leak out and this is not always there so some have this leaking issue while other do not. It is interesting that the Shrader, for me, does not leak. have gone the route as a quick fix of putting a Presta to Shrader adapter on the Presta valve to get me pumped up.