Originally Posted by
HillRider
As Looigi noted, not all Presta stems are threaded and those nuts serve only that limited purpose. I discard them because the are a nuisance when you do have to repair a flat, both to remove the tire/tube and to reinstall it. Pressing with my thumb is easier.
They also serve to keep the stem in a radial orientation, reducing the risk of tear flats at the stem base.