Is there any reason to leave these damn things on my bike?
 

They're constantly coming loose and rattling, and then there's always the possibility I can kill the tube by over tightening them after I inflate. Is there any reason to keep one of these valve nuts on the valve?

I find that valve nuts make excellent water bottle cage spacers, in those cases where the bottle cage would otherwise interfere with the front derailleur clamp band.

Other than that, I haven't found a use for them.

IF you have a Silca style push on pump head they are usefull as they hold the valve in place as you push the head on. And that was me trying real hard to find at least one excuse to use them. I do like to keep the caps on my MTB and cross bikes to keep the mud out though.

Sometimes they help stop that annoying ticking sound the valves can make on some wheels

I have always felt they help protect the tube from being cut by the rim hole where the stem and the tube meet.

I always use no thread valve stems. The pump goes on much more easily. Nuts are not an option.

They are nice spacers.

When I ran a service department I would try my best to source tubes with smooth valves so customers couldn't use those things or ask for them.

I realize the OP has traditional tubed clinchers, but for the tubeless crowd, these are pretty much essential, right? Because otherwise, there's nothing but air pressure holding the valve stem up.

Sorta yes.

But you use a completely different valve as you likely know.

ive seen someone push the pump's head onto the stem and dislodge the bead because the stem acted as a battering ram against the inside of the tire. they didn't realize it, made it out the door, and blew that tube pretty quickly.

I do have tubless MTB wheels but that stem does seem to be in there pretty tight, but that's a good point that I had not considered.

Not really a reason for that black plastic cap either.

btw when I run tubes i like Michelins b/c they aren't threaded.

SPP

I had some carbon rims where the valve rattled on the rough roads. These things tightened it down. No more rattling.

I just bought a set of carbon wheels that came with a couple of rubber grommets to center the valve stem. Haven't tried it, but then I've always just gone with a bare stem. We'll see....