What's This Nut For?

October 12, 2017 - Scott Wilson answers a burning question on our guest blog.

What’s this nut for?

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

It’s 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 (photos below). Once there’s 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 — fighting to get the valve out of the rim.
  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. And 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. And 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 the 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 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 or on Adventure Cycling’s Facebook page.

Photos by Scott Wilson

Scott Wilson is a recent graduate of Columbia College’s MFA, nonfiction writing program, a nine-year veteran bicycle mechanic, and long-time reader of Adventure Cyclist magazine. He lives in Chicago and his writing can be found in anthologies by the Chicago Center for Literature and Photography, and the Chicago Anthology by Belt Publishing. His personal blog, where he writes about the technical aspects of cycling from an insider’s perspective, is BikeBlogorDie.com 


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Ralph Sherwood Schwer October 17, 2017, 3:04 PM

Here in Australia we got rid of fiddly, useless presta valves over sixty years and completely replaced them with Schrader car valves, which are so much easier to pump up. While living long term in Vietnam, where bicycles come with presta valves, I immediately changed to Schrader valve tyres. If they work on racing cars, they can definitely work on bicycles. ALL bicycle tubes should use Schrader valves.

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