Is Presta valve lock nut useful?

[ManBearPig]

Ciao.
I have always had lock nuts with Presta valve inner tubes on my Giordano road bike, but there are a few guys I know who take them off. I understand that there is a chance that you can overtighten a lock nut and therefore irritate the tube in a way.

Do you leave lock nuts on and why? Have you experienced any advantages & disadvantages of having a locking nut?

[Painkiller]

There are pros and cons to each valve system. as for the Presta the lock ring is a Pro. it keeps stem in place should the tire become to low to push the pump valve on. Great feature! Finger tight is all u need to do once tire is inflated. For this reason I prefer schreader tubes with this type of stem also

[Jesper]

(03-06-2021, 08:00 AM)ManBearPig Wrote:  Do you leave lock nuts on and why? Have you experienced any advantages & disadvantages of having a locking nut?

I agree with Painkiller.
I have always used them, and have never experienced any problems. On my regularly used bikes that get higher mileage/Kms; I use 2. I do not over tighten the one at the rim, but I tighten the 2nd one hard to the other which acts as a "jam nut" and keeps both from loosening. Never an issue with that method, nor any tube damage.
I also tend to cut a small rubber "washer" made from old tubes and place it down on the valve stem before tube installation; Presta and Schrader. It needs to fit tight around the stem; I have to stretch it a bit. I always do this when using high pressure tires (>95 psi/6.5 bar); I usually ride at >120 psi/8 bar. It prevents the tube from pushing into the rim orifice and potentially damaging the tube in that area; especially if the rim tape has shifted over time. When installing a new tube I only tighten the nut enough to keep the tube in place. Once tube and tire installation is complete, including inflation, will I tighten the nut to the rim and add my "jam nut". On most rims (vintage, anodized, painted, chromed, and/or new) I use a small nylon washer between the nut and the rim to keep from marring the rim surface, always finishing using the second "jam nut" with that type of application.
I would venture to say that a few riders may exclude using them as a another means of weight reduction; and here I am adding more!