This Presta valve core, here removed, has been a nuisance since day one. Once inflated, it holds the pressure well for a trip to the trails, but after 3-4 days, the wheel is flat again. The volume (29"x2.5") is a lot to be lost so quickly.
It's anyway good practice to inflate the wheels every time one goes riding, but I'd much rather not see the rim on the ground with the chequered carcass pattern of the tire showing outside.
I've been tightening the core using a valve core tool. I'm torquing by hand only, as it seems too small and too fragile. If I tighten really hard, the rim will at least remain off the ground for two days, but still, too much pressure is lost.
I'm not sure I should be using a wrench, or even a torque wrench. How do I stop a removable valve core from leaking?
The rubber seal (black part in the picture) seems to be what holds the air inside. Should I pay particular attention to twisting the top nut after inflation?
(I'm using a foot pump and not a hand pump, and so inadvertently unscrewing the core while removing the chuck should not be the culprit.)
The present question is a duplicate.
Even if the valve core comes out clean with no sign of sealant deposit, as in the picture above, one may well still have a tubeless setup.