What's this nut for?

Above is a picture of a presta valve, exploded. You see the stem, the valve core, the cap… and that weird little nut.

This is an installation nut, or a jam nut. Its job is to keep the valve from sinking into the wheel when you try to pump up the tire. Once there is enough air pressure in the tire to keep the valve from going under, the nut’s job is done and it should be removed.

There are several good reasons to remove the jam nut after the tire is pumped:

1      .     It rattles

2      .     It can corrode and fuse to the valve stem, making a simple tire change into a Herculean task

3      .     It adds weight

4      .     In cold weather it’s one more little metal thing you have to take your gloves off to mess with to change a flat

5      .     If it’s screwed down too tight it will squeeze the rubber tube against the edge of the rim hole and over many cycles of deflation/inflation and the normal wiggles and movements of riding it will cause a cut.

And there are a couple good reasons to keep it on:

1      .     It’s shiny

2      .     If you’re in the habit of letting your tires go completely flat, keeping it on might make re-inflation easier.

Most people these days are using extra-long valve stems and don’t need installation nuts at all. This trend is reflected by the increasing popularity of smooth, threadless valve stems.

There’s also a belief that that the installation nut will keep the valve from rattling. This is sort of true as long as the nut stays tight against the rim, but that picture above proves why that’s a bad idea. If you have problems with the valve shaking about, do like the pros and stack up a few layers of electrical tape, put a hole in the middle, and put that over the valve, like so:

But just because installation nuts aren’t particularly necessary doesn’t mean you should throw them away. They have lots of subsidiary uses, like acting as spacers when installing a rack:

Or they can be used as bracelets for your doll collection:

Or you can make a necklace out of them. Be creative and post your installation nut uses in the comments below.