By Scott Wilson
What’s this thing for?
Here 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:
And there are a couple good reasons to keep it on:
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 washers or 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.
Scott Wilson is an MFA writing student at Columbia College as well as a seasoned professional bike mechanic. Scott’s “wrenching” experience includes bike shops, racing teams, and professional triathletes across the US. The aim of Scott’s technical articles is to explain in detail how bicycles and their individual components work...and in doing so, help you keep your own bikes running better and lasting longer.